The Neurochemistry and Molecular Biology of Behavior
Karen L. Overall, MA, VMD, PhD, DACVB, ABS Certified Applied Animal Behaviorist
Center for Neurobiology and Behavior, School of Medicine, Psychiatry Department, University of Pennsylvania
Philadelphia, PA, USA

Introduction

The behavior of any animal is the result of some complex integration of all organ system responses. As such, behavioral signs of any condition are non-specific. Behavioral phenotypes are the result of dynamic processes occurring at regionally specific brain regions which the affect both the behavioral phenotype and the neurochemical response. Response depends on both the characteristics of the neuronal cell types and their projections and is tightly linked to molecular responses associated with the various receptors. The extent to which this extremely plastic process is responsive to environmental input may be constrained by a 'genomic response surface' that acts to define boundary conditions (1). The complexity involved in behavioral responses is the prime reason why they are so poorly understood, except in their extreme forms. Yet the single most common reason clients seek help for their pets--regardless of the pathology--involves a behavioral change. Because all physical conditions can be affected by anxiety, and all behavioral conditions can worsen when an animal becomes physically ill, a modern understanding of veterinary behavioral medicine must involve a mechanistic approach that seeks to understand complexity, rather than to ignore it. While daunting, it is exactly this approach that has provided us with some baseline for a molecular understanding of learning, insight into the potential cellular and neurochemical effects of behavior modification, and a rationale for pharmacologic intervention that ameliorate behavioral pathology, instead of suppressing or masking non-specific signs.

Learning

Most veterinarians have had little training in behavior, neuropharmacology, or behavioral genetics. Hence, we lack the basic information that will allow us to understand learning--whether as a result of routine exposure or the artificial construct of behavior modification--at any kind of mechanistic level. Only by removing behavior and learning from a 'black box' approach and attempting to understand at least some aspects of these processes at the cellular level, can we begin to understand why certain interventions produce alterations in phenotype.

Associational learning occurs primarily in the hippocampus, and is a special case of neuronal plasticity (2). Repeated, high-frequency stimulation of any neuron results in increased efficiency of receptor stimulation of second messenger systems. This is the first phase of 'cellular' learning and memory. If this stimulation is repeated sufficiently often the continued stimulation of second messenger systems stimulates neurotrophic factors to induce gene transcription and protein translation.

Reward structures

It's important to understand reward structures and what these mean at the cellular and molecular level for behavior modification. Behaviors are reinforced or learned best if every time they occur they are rewarded. At the cellular level, repeated reinforcement insures better, more numerous, and more efficient connections between neurons (3,4). Stimulation is induced when a neurochemical in a synapse triggers a receptor to engage it. This stimulation of the receptor engages second messenger systems in the post-synaptic cell, usually cAMP. The result is cellular memory or long-term potentiation (LTP). By itself, this initial process represents E-LTP or early phase LTP and STM (short-term memory). The process is short-lasting, RNA and protein-synthesis-independent, and the result does not persist or become self-potentiating unless the stimulus is consolidated into L-LTP late phase LTP, which is a more permanent form (5). E-LTP can be induced by a single train of stimuli in either the hippocampus or the lateral amygdala.

In contrast, L-LTP and LTM (long-term memory) requires repeated stimulation of cAMP, induction of cAMP response element binding protein (CREB--a nuclear transcription factor), and is long-lasting, protein synthesis dependent, and is RNA transcription dependent (5). When stimulation continues, BDNF enhances neurotransmission and potentiates what is called activity-dependent plasticity at synapses (e.g., learning), particularly in the region of the brain most involved in learning, the hippocampus. This effect can also occur in the lateral amygdala and is one modality postulated to be involved in learned or conditioned contextual fear (5).

This neurobiology is important to consider in the context of reward systems. It explains why continuous reward works best in acquiring a behavior (E-LTP and STM) and why intermittent reward acts best to maintain a learned behavior (L-LTP and LTM). This neurobiology explains why a really excellent reward (jackpot) can help you learn or reinforce a behavior quickly and why a really horrible experience can stimulate the amygdala to encode learned panic or phobia. The amygdala, itself, is an incredibly complex few cubic mm. Almost all outgoing tracts that control some higher forms of integration of behavior in the cerebral cortex, hypothalamus, brain stem et cetera have their efferents shaped by the location of their origin in the amygdala (6). Additionally, the lateral amygdala is likely the site where memories of conditioned (learned) fear are created through a process involving neuronal plasticity (5). In fact, if one lesions or inactivates the lateral amygdala, it is impossible to either acquire a fear or to express a previously acquired fear (7).

Psychopharmacology--roles for neuronal stimulation, synaptic plasticity, and receptor protein translation and transcription

Medications are now routinely used to treat behavioral concerns. They are likely not used often enough in the early phases of anxiety, and remain almost completely unexplored as an aid in helping to train dogs to learn complex tasks better and faster. This should change soon as preliminary data for rodents have been very promising. The best drugs to help treat behavioral conditions are the tricyclic antidepressants (TCAs) and the selective serotonin re-uptake inhibitors (SSRIs). These 2 classes of drugs and their descendants have made the use of broad-acting compounds like progestins, tranquillizers, sedatives, and anti-convulsants, at best, anachronistic. What makes TCAs and SSRIs special and why are they so useful for anxiety disorders?

The key to the success of these drugs is that they utilize the same second messenger systems and transcription pathways that are used to develop cellular memory or to "learn" something. This pathway involves cAMP, cytosolic response element binding protein (CREB), brain derived neurotrophic factor (BDNF), NMDA receptors, protein tyrosine kinases (PTK)--particularly Src--which regulate activity of NMDA receptors and other ion channels and mediates the induction of LTP (long-term potentiation = synaptic plasticity) in the CA1 region of the hippocampus (2, 8, 9).

There are two phases of TCA and SSRI treatment: short-term effects and long-term effects. Short-term effects result in a synaptic increase of the relevant monoamine associated with re-uptake inhibition. The somatodendritic autoreceptor of the pre-synaptic neuron decreases the firing rate of that cell as a thermostatic response. Regardless, there is increased saturation of the post-synaptic receptors resulting in stimulation of the -adrenergic coupled cAMP system. cAMP leads to an increase in PTK as the first step in the long-term effects. PTK translocates into the nucleus of the post-synaptic cell where it increases CREB, which has been postulated to be the post-receptor target for these drugs. Increases in CREB lead to increases in BDNF and tyrosine kinases (e.g., trkB) which then stimulate mRNA transcription of new receptor proteins. The altered conformation of the post-synaptic receptors renders serotonin stimulation and signal transduction more efficient (10, 11). Simply, TCAs and SSRIs work so well because they stimulate the neurochemicals involved in anxiety-related pathways, and because the augment the rate at which learning occurs because of the parallel effect on pathways and mechanisms involved in learning.

Knowledge of the molecular basis for the action of these drugs can aid in choosing treatment protocols. For example, the pre-synaptic somatodendritic autoreceptor is blocked by pindolol (a -adrenoreceptor antagonist) so augmentation of TCA and SSRI treatment with pindolol can accelerate treatment onset. Long-term treatment, particularly with the more specific TCAs (e.g., clomipramine) and SSRIs, employs the same pathway used in LTP to alter reception function and structure through transcriptional and translational alterations in receptor protein. This can be thought of as a form of in vivo "gene therapy" that works to augment neurotransmitter levels and production thereby making the neuron and the interactions between neurons more coordinated and efficient. In some patients short-term treatment appears to be sufficient to produce continued "normal" functioning of the neurotransmitter system. That there are some patients who require life-long treatment suggests that the effect of the drugs is reversible in some patients, further illustrating the underlying heterogeneity of the patient population considered to have the same diagnosis.

Relevance to aging dogs and cats

The neurochemical processes associated with cognition are the ones affected in aging cells. The receptors, channels, and components of the cellular response associated with learning are impaired in aging (12). The variants of aging most studied in dogs and cats primarily involve those where amyloid production or degradation is impaired (13-15). Mental stimulation, exercise, and daily anti-oxidant administration have all been shown to delay brain aging, and, or reverse some of the damage and restore some cognitive function (16-18).

Results have been more dramatic in dogs than in humans, in part, because we can constrain dogs to eat a relatively invariable diet in which large amounts of anti-oxidants may affect palatability.

These diets, or supplements that mimic the effects of the diets, appear to work best when mental and physical stimulation is also present. Most pets in industrialized countries are under-stimulated. Aerobic exercise is experienced only by the exceptional pet dog, and dog patterns of exercise tend to mimic those of their humans. Furthermore, old dogs and cats are seldom mentally stimulated. Clients should be encouraged to ask their dogs and cats to perform reasonable tasks (e.g., bring a specific toy), and they should incorporate as many 'puzzles' into daily life as possible. This could be as simple as holding a treat in one hand and asking the dog or cat to choose which, or feeding animals who eat dry food in treat balls. Other suggestions for how to enhance the life of aging animals can be found in the companion handout included (19).

The key to modern behavioral medicine lies in our ability to formulate and test hypotheses of mechanism in a rigorous manner using the arsenal available from fields not usually associated with clinical endeavors: cellular biology, molecular genetics, and neurobiology.

Protocol for geriatric animals

We all age, and some of us do it a lot better than others. The same is true for your cats and dogs. Cats can be considered middle-aged starting somewhere between 8 and 9 years and entering old age when they are 13 or so. For dogs the issue is more complex because the larger the dog the shorter the life. This association has yet to be well explained, but there is some association between size and cell growth that is likely important. That said, if you have a toy breed, they may follow a cat-like pattern. If you have a medium-sized breed (25 kg), the dog is middle aged somewhere by 7-8 years and becomes old by 10-11 years. Larger breeds are middle aged by 6 years and old by 8 or 9 years. Thinner dogs live longer than fatter ones and may age differently. As for humans, aging for dogs and cats has never been a more palatable experience, but we need to understand the joint physical and behavioral needs of aging to insure the healthiest outcome.

Play and exercise

People assume that their dogs and cats slow down and won't play as they age. This assumption is likely wrong, but will become self-fulfilling unless the clients change their own behaviors. If people assume that dogs and cats stop playing when they are out of puppyhood or kittenhood they will not play with them. This is wrong. The best way to prepare for a successful and healthy old age is to prepare for a successful and healthy adulthood.

Leash walking

All dogs and cats--yes--and cats--benefit from leash walking. Leash manners are best taught when the animals are babies. If cats become accustomed to harnesses and leashes when they are young they will be willing to exercise on a lead when they are older. Mental stimulation is part of exercise. When your pet goes for a leash walk they are not just exercising their legs: they are exercising their nose, their brain, their social skills. All of these need stimulation. New data on humans shows that exercise provides for muscle health, but also has far-reaching benefits on how well neurons in the brain function. We need to remember that--no matter what their age--animals just left in the yard by themselves neither get the exercise they want and need, nor do they get the mental stimulation. If you doubt this--videotape your dog the next time he or she is alone in the yard. This is where outdoor cats have it all over dogs who are locked behind fences: they at least get to explore and contribute to the wide-spread olfactory and social environment. The trade off for cats is that fewer outdoor cats make it to old age than do indoor cats. The same is true for dogs who free-range. There is simply no way around it: all animals benefit from leash walking, and all animals should be comfortable on a lead.

As dogs and cats age they may experience arthritic changes in their neck and spine. Accordingly, the lead and collar style you have used for the youngster may not be appropriate for an elderly animal. Regardless, the tools you choose should do no harm. This is the best argument for choosing head collars and harnesses as restraint and guidance devices throughout life.

As the dog or cat slows they will still enjoy slightly more sedate leash walks. It's the client's job to learn what the distance limit is and prepare for it, either by knowing when to turn around, or having a car or cart available to take the dog or cat home. Very elderly dogs and cat may miss exploring the olfactory and social environment. A well padded cart, wagon, or wheel barrow can redress this concern if it is well oiled and maintained and gently pulled.

If your pet is accustomed to doing a job for you on their walks (e.g., carrying the mail or a newspaper) insure that they can still do this comfortably. This means insuring that their teeth aren't hurting and their neck is not so arthritic that carrying the object causes pain. Dogs and cats will endure horrible pain to please, and we do a less-than-adequate job of assessing pain. If your pet cannot carry their usual package, make a new one for them. This is could be a lighter paper, a toy, or some other object that is light and allows them to participate in your life.

Running with other dogs or cats at play groups

If your dog or cat enjoyed running or playing with other animals as a youngster, they will not want to give this up in old age. Play with a member of your own species is also a terrific form of physical and mental stimulation where non-vocal signals conveying concern or level of ability / debility will be easily recognized. This means, though, that you have to pick your play group or play mates. Companions that are evenly matched by temperament, ability, and size are even more important the older the dog or cat gets. You do not want your older pet to be injured or frightened. Smaller groups or pairs of animals--always supervised--are ideal. Make sure that you always carry water and dishes, towels, and a few treats to reward good behavior. Watch to insure that your pet is not becoming exhausted: stumbling, deep, erratic panting, and moving away from other animals are all signs of this. If your pet is not ready to leave, but needs a rest, take the dog or cat away from the others, offer them water, wipe them down with a damp towel, if needed, and have them lie down on the towel or blanket you have provided. Sometimes watching other dogs or cats play is enough. If you fear that there is any risk of heat exhaustion buy and carry with you one of the newer pads that contains a gel that acts as a coolant for your pet when they lie on it. If your pet becomes incoordinated and cannot attend to you at any time--take them to the vet immediately. Heatstroke is an emergency. Remember--older animals experience stresses more profoundly and more acutely than do younger ones. Again, be prepared to carry or provide transport for elderly pets who are tired.

Car trips

Trips in cars will always be enjoyable, if the dog or cat enjoyed them as a puppy or kitten. Even a dog or cat who is deaf, blind, and arthritic will enjoy a car ride if they did so earlier in life. The tactile sensation of motion and air, the olfactory stimulation, and the pure comfort of being included in their people's daily lives do not diminish with age. In fact, the value of these outings may increase as the animal loses access to other activities they may have enjoyed. Cats are relatively easily picked up and placed in the car on a bed or blanking with a seatbelt through the harness, or in an open crate. Dogs will need more help. There are now at least a ½ dozen commercially available ramps that help dogs enter and exit cars--and boats. Very arthritic dogs will still need help getting out: down is harder than up and gravity is going to help them fall if they are unsteady. Once in the car, padding (a bed or blanket) and a seat belt, crate, or barrier is essential. Older dogs move less easily and can only slowly compensate sudden changes. They must be protected during these trips. Be aware that older animals may be more sensitive to temperature extremes, so dogs and cats who always went with you in the late fall and early summer, may not be able to do so now without suffering--perhaps fatally--from cold or heat that you did not think was extreme.

Pain and very aerobic activities

Many people whose dogs participate in higher levels of obedience, agility, frisbee, flyball, et cetera worry about aging, pain, and performance capabilities. Your first concern must be the well-being of the dog. Aging can be viewed by the dog as a release from punishment if he or she has been unfortunate enough to have lived with someone who demand perfection in a competitive activity, and for whom nothing is good enough. One could hope that most people reading this handout will not fall into that category. If the dog really enjoys the activity but is increasingly struggling with jumps, catches, et cetera, consider massage, hydrotherapy (usually swimming), supplementation with nutriceuticals or specially formulated food, and, or anti-inflammatory agents. The number of anti-inflammatories available for dogs and cats is growing daily. These can be used to relieve and prevent discomfort (as with humans they are best used before the pain is felt), but should never be used to push the dog to a level that the human demands. Periodically step back and ask yourself what is in the dog's best interest. All competitive activities can be modified for older dogs: jumps can be lowered, frisbees can be thrown horizontally and a shorter distance, as can balls, courses can be shorter, et cetera. Even herding dogs can get help: I've seen farmers drive elderly collies to the sheep who need to be moved, have the dog do what's needed, and then pick the dog up and put him or her back in the truck or cart. This way everyone's needs are met. Remember, if your pet worked in any capacity, they still need to feel useful. The extent to which they need to work to feel useful will vary between animals and your job--as your pet's ultimate caretaker--is to learn what will humanely work for your dog.

Swimming is as good for dogs and cats as it is for people. Physical therapy for health and to address injury or aging is still not common for pets, but there are centers that offer canine or feline swimming. These facilities are ideal in that they have life vests, have created pools where animals will not panic and where they can feel their footing, et cetera. You can create the same types of environments at home with some effort. It may be that you have an out-of-ground circular pool that's a uniform 4-6 feet deep. Fit a life jacket to the pet. Get in the pool. Have someone gently hand you the pet. Shepherd them around the pool encouraging leg movement. Do not let your pet become tired or scared. Hand or gently haul the pet from the pool (some canine life jackets come with handles for this purpose), and towel dry. If you start with short swims, the pet can and will work up to more aerobic and strengthening activities if they enjoy the water. If possible, do what hydrotherapy facilities do: heat the pool. If you cannot do this, pets can go in hot tubs if and only if:

 The temperature is not at it's maximum,

 The jets are off,

 No chlorine is involved,

 The pet is supervised (which means you are in the tub with them),

 The time spent in the tub is short,

 You do gently perform range-of-motion exercises with their limbs, and

 The pet cannot become chilled when taken from the tub.

Also, pet hair clogs filter systems. You'll need a plan to deal with this.

Please be aware that older dogs and cats who are blind fall into and drown in pools every year. This can be prevented with adequate supervision and fences.

Support for the failing--carts and slings

Physical instability and pain is linked to anxiety. Many animals who could get more exercise are afraid to do so either because they hurt or they are concerned that they will not be able to recover. The time to begin to use carts, slings, or manual help is before it is needed. Perhaps the dog needs to be supported in a sling or with a hand under their rump only occasionally to go up the stairs. Knowing that there is help, if needed, will not only allow the dog to continue to use stairs, but will allow the animal to develop a signal system with their human indicating which days require help. This signaling can be as simple for the dog as standing at the bottom of the stairs and looking up. Likewise, carts don't have to be an 'end of mobility' decision. Instead, they can provide support and mobility at times when the animal is weaker, but still cognitively be able to learn to use such support creatively. Investigate these options--which are growing for dogs and cats--before you need them. If you don't like the idea of carts and slings, one option as you, the human, ages is to only obtain dogs that are of a size that you are sure that you can always carry.

Diet, treats, and eating

As pets age they may become 'finicky'. Fussy behavior may be the result of mouth or tooth pain or some change in digestive function. Here's where you need to insure that your older animal is healthy. You should have a physical exam with complete lab work at least once a year when the animal becomes middle aged. Do not wait until your pet is ill--a baseline lab evaluation will allow your vet to recognize changes early and to learn how long laboratory values have been out of whack. This information is critical to determining the type and quality of care your pet will receive as he or she ages. As animals become older, it may be reasonable to have check-ups every 6 months. Ask your vet.

If your pet needs professional dental care do it as soon as possible. Dogs and cats who cannot chew their food experience a loss of pleasure from one of the most pleasurable activities of their lives. They also have gastrointestinal upset because the food is not well processed before getting to their intestines. You should have been brushing your cat's or dog's teeth all their lives, but if you have not--it's not too late to start and there are many products that can facilitate this. Depending on how well your dog or cat processes their food, you may wish to change diets with age. If your pet has a favored biscuit, they can likely still have this although for some animals on protein restricted diets the protein in the biscuit will have to be factored into their overall diet. Talk to your vet. Also, even if your dog's or cat's lose teeth, they can still enjoy biscuits and food toys if there is no pain in their mouth.

A sudden change in eating behavior in an older animal should warrant a visit to the vet. This is one reason why you should watch your pets eat so that you know what normal is for your companion.

All clients should be aware of the incredible developments that have occurred in the pet food industry in terms of supplements and foods specially formulated with anti-oxidants, the 'anti-aging' compounds. In controlled studies, these foods and supplements have been shown to increase a pet's willingness to be active, to retain cognitive abilities, to interact well and with enjoyment with humans and other animals, to sleep well and with fewer disturbances, and to retain house training. These studies have all shown that the anti-oxidants help, as does exercise and mental stimulation, but the largest effects are for the combination of the anti-oxidants and mental and physical stimulation. This will work for your pets, it should work for you, and you should do it!

Elimination behaviors

As dogs and cats age they can become arthritic and confused, just like us. Pain and joint immobility can be associated with an unwillingness to eliminate as the dog or cat had previously. In some cases this then leads to a cycle of constipation followed by diarrhea. Fecal material that is retained continues to lose water to the colon. The feces then become hard and are difficult to defecate. As the intestinal tract fills, the urgency associated with this imbalance then leads to defecation of hard feces followed by diarrhea. Whether it causes pain or not, at some point we have no choice--we must eliminate. By addressing the pain and mobility issues, we can prevent this messy cycle that upsets pets and clients, alike.

Regular exercise promotes regular digestion. Anti-inflammatory pain killers will allow pets to maintain or increase exercise as discussed above.

If water and food dishes are at head height cats and dogs who have arthritic necks will be able to eat and drink without pain and so will eat and drink more normally. Water or broth can be added to all foods to make them easier to chew and swallow and to provide more water for digestion. In this age of microwaves, all feline and canine meals can be warmed to make them easier to chew and to aromatize the volatile compounds in the foods. Stimulating the sense of smell often increases intake.

Agents that address constipation can be regularly added to the meals of older animals. Psyllium, the same bulk-forming agent used for humans, if added to meals with water will make the feces softer and easier to pass. This is really important for animals whose hips are less mobile and those whose hips hurt. For pennies a day, cats can have 1/4-1/2 teaspoon of psyllium mixed into food, and dogs can have ½-2 teaspoons, depending on size, type of food, and activity level of the dogs.

As hips fail, and as pain increases, dogs and cats may be less able to control their urination. It may be too painful to maintain a full bladder, or it may not be neurologically possible to do so. There are a couple of simple changes that can be implemented that will make the pet's and client's lives easier.

 Dogs can be taken out for leash walks earlier. Don't wait for the dog's bladder to be full--let the dog empty his or her bladder before it's full. This will insure that if there is a leak, the leak will be small, and also that the dog will get more exercise and more stimulation, which will help them remember to eliminate when given the opportunity.

 Dogs can also be taught to use a canine litter box. These are now commercially available. This will involve retraining the dog, so the client who is considering this needs to do it while the dog is still capable of learning new associations. For very little dogs, or for dogs who are at high risk for hip dysplasia and other mobility problems, clients may wish to dual train their dogs to eliminate in these boxes and outside as usual. This is also a good recommendation for people who intend to travel with their dogs and stay in hotels.

 Dogs can be diapered. Long haired dogs should be trimmed to help with this. If this is the choice the clients MUST be prepared to change the diaper often, clean and dry the dog, and apply an unscented cornstarch powder to creases. Urine scalding and bed sores are considered signs of neglect and, or abuse in dogs.

 There are medications that will help older dogs who have decreased bladder muscle tone, regardless of cause. Most of these medications involve phenylpropanolamine (PPA) or a similar compound, and can be used safely in dogs if laboratory and physical exam is performed and the clients maintain a good dialog with their vet.

 Steps are a problem. Clients can either carry dogs or, if the dog is big, build ramps or use carriers that help support the dog to allow them access to the outside. Dog doors must be 'handicapped accessible'. This may mean removing the bottom lip and make them flush with the floor.

 For cats, litter boxes may need to be made lower. Cookie sheets or shorter litter boxes with the side cut out can help.

 Cats should not have to go any further than they easily can to find a litter box. This may mean that the clients need one litter box per room. While less than aesthetically pleasing, this is not a difficult situation to maintain and the boxes can be removed and the cat placed in a smaller, provisioned area if the client wishes to have a party or guests who won't understand.

 Cats develop arthridides and hip dysplasia, also. This means that stairs can be a problem. If the cat has problems, they cannot be expected to go up and down stairs to eliminate--regardless of how they had behaved in the past. A litter box must be available where the cat stays. If cats had been previously accustomed to jumping up to a litter box, perhaps to keep the box away from dogs, a new plan will have to be devised. Clients can invariably be creative when they have to be.

 Cats who use cat flaps may need to have a flap that moves more easily and one that requires less of a step. Doors that are flush with the floor, without lips, prevent tripping.

Sleeping

Changes in sleep cycles are common with age. When cognition begins to fail, the alterations become tremendously abnormal: animals pace aimlessly at night and sleep deeply during the day, the pacing may end with the animal in corners or vocalizing with no object of the vocalization apparent to the client, et cetera. Good exercise and diet, and comfortable sleeping areas, may help older animals sleep better and more regularly. The dog or cat who may never have had a bed needs and deserves one in old age. Dogs and cats who are painful for any reason need beds with orthopedic grade foam. These are now readily commercially available. All bedding should be washable. This is not only for the sake of the pet--anything that makes the client's life easier will help with the maintenance of the animal.

If the sleep changes are truly extreme, it's time to talk with your vet about medication. There are commercially available cognitive enhancing and, or anti-anxiety agents that work. This is a quality of life issue, and medication can provide that quality.

Interactions with other animals

The longer animals can maintain relationships with other animals the better. Most animals are very good at reading non-vocal signals and if they know the elderly cat or dog will not insist on impossible or painful interactions. In fact, clients could learn from watching how other cats and dogs treat their elderly companion.

The introduction of a younger animal to an older pet can be both a godsend and a bane. Painful cats and dogs, deep in the stages of terminal old age, will not have the physical or mental plasticity to tolerate pain and endless invitations to play. However, having a younger animal around the elderly one can stimulate the old cat or dog mentally and physically in a good way. If the client does not also have an adult animal or another youngster who can take the brunt of the play, they may wish to consider getting one. Otherwise, the clients will have to wear out the youngster and protect the elderly pet from unwanted attention while insuring that they also have the company and stimulation.

The ideal time to get a younger pet is as the older animal is entering late middle age. The 8 year old dog who you thought would never play again not only will play, but will look like a puppy. Additionally, by acting in the role of 'foster parent' to the new baby in the house, all mental faculties are well exercised. Another pet can add years to the life of the older animal, and improve its quality in ways we likely do not fully understand.

Stimulating the nose and the mind

We now know that there is some association between measures of cognition and growth, maintenance, and function of the olfactory neurons. The olfactory neurons are unique in the world of nerves because they are only 1 cell away from the outside world in the olfactory epithelium within the nose, and this is the only nervous tissue that continues to regularly grow and regenerate throughout life. When humans begin to suffer cognitive losses we also note that they have an impaired sense of smell. Whether by stimulating smell we can enhance cognition is unknown, but in animals for which their most complete information comes from scent, we must assume that the maintenance of the olfactory system is not independent from that of the cognitive system. Let your dog or cat use their nose. Take them on walks where you have hidden treats. Use food toys where the pet has to work to get special food (assuming that the physical state of the animal is coupled to the difficulty of the toy). Create food puzzles using upended flower pots, rocks, and hollowed bones all placed on trays with food in the hidey holes. Let dogs and cats explore the scent world outside. Take them to new areas since the data show that dogs and cats sniff more when they are in unfamiliar environments, or when they are on trails that other animals pass.

Massage and physical manipulation

Dogs and cats can benefit from deep muscle massage and range-of-motion exercises, as do we as we age. Because canine and feline sizes and musculature vary considerably, talk to your vet about the right kind of pressure to exert that does not cause pain or anxiety. Many massage therapists are now also willing to take canine patients or to teach clients basic massage techniques. This has a dual benefit: giving a massage can be almost as relaxing as getting one.

After injury, or as aging changes your dog's or cat's mobility, range-of-motion activities can help prevent or regain lost function. Limbs should be slowly but firmly moved through an entire cycle of movement. Before you can be successful at this you need to know how the limbs of dogs and cats naturally move. The time to best learn this is when your pet is young and more tolerant. Discuss with your vet if this option can help your pet. If so, have your vet demonstrate the range of motion and practice on a compliant animal first. Any animal who becomes fearful, resistant, or aggressive should be re-evaluated. Many cranky animals, in fact, become more docile because such activities decrease pain and stiffness.

Finally, anti-inflammatory medications and those that address pain (analgesics) are now widely available by prescription from your veterinarian for cats and dogs. There is no longer any reason for dogs or cats to suffer without redress.

Manipulations--ear, teeth, nails, and coat care

Any dog or cat who resented or fought maintenance care when young will tolerate it less when old. But the older animal needs such care more. Overgrown nails will make it harder to walk on already painful joints, ear infections and waxy buildup will further compromise hearing, bad, infected, and loose teeth will compromise nutrition, and mats that hurt will make a dog or cat who is globally more painful overly reactive. Old age is not the time to muscle an animal into some restraint posture and do everything, forcefully, at once. Actually, there probably never was a time when such force was a good idea, but it is a particularly bad idea for elderly animals. Instead, use a soft washcloth and delicious toothpaste to work on 1 or 2 teeth a day. Trim one paw or a few nails on that paw at a time. Soak ears one day, and clean them over the next day or 2 and then repeat. Choose which section of the pet to groom if a whole-body groom is too scary or painful. Trim coats, if warranted. A short clip can make an elderly cat or dog feel, look, and move in a more sprightly manner. The resistance to such clips is all ours: it's we who worry that the pet won't live long enough for the coat to grow again. Put the pet's needs first, and you may find that for many years you maintain a clipped pet who is a constant state of having some part of their toilette done. If they are happy and unafraid, this is good.

End notes

The suggestions discussed above are simple, and they can help repay--just a little bit--of what our best furred friends so freely and generously provide us. It's not fair that dogs and cats don't live as long as we do, but they can live well and happily even as they pass through their last years. We will become better and more humane people for insuring that this is so.

References

1.  Overall KL. Pharmacological treatment in behavioral medicine: The importance of neurochemistry, molecular biology, and mechanistic hypotheses. The Veterinary Journal 2001;62:9-23.

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19. Overall, KL. Protocol for Geriatric Animals. From: Manual of Clinical Behavioral Medicine for Small Animals, Elsevier, St. Louis, 2005.

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Karen L. Overall, MA, VMD, PhD, DACVB, ABS Certified Applied Animal
Center for Neurobiology and Behavior, School of Medicine, University of Pennsylvania
Philadelphia, PA


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