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Dog Brain Chemistry and the Use of Medications and Behavior Modification

Adrienne is a certified dog trainer and former veterinarian assistant who partners with some of the best veterinarians worldwide.

Brain chemistry can cause fear and aggression.

Brain chemistry can cause fear and aggression.

The Role of Chemical Imbalances in Dog Behavioral Problems

If you own an aggressive or fearful dog, you may be wondering what may trigger those bouts of aggressive or anxious displays you witness and how medications may play a role in the recovery process. Just as in humans, chemical imbalances may occur in your dog's brain and can play a primary role in the behavior of your dog. Taking a look at your dog's brain chemistry may be helpful in many cases. Let's take a virtual walk into your dog's brain so to have a generalized sense of what may be possibly going on in there.

In This Article

  1. What's in Your Dog's Brain and How Does It Affect His Behavior?
  2. What Medications Are Used in Dogs With Behavioral Problems?
  3. Do Medications Help Dogs?
  4. My Experience With Medications vs. Behavior Modification

What's in Your Dog's Brain and How Does It Affect His Behavior?

The brain of a dog is ultimately quite similar to the brain of humans in many ways.

  • They both include a limbic system, where emotions and memories are stored.
  • Also, both brains share the same basic neural chemistry, explains Stanley Coren.
  • This means that just as humans, dogs may suffer from emotional problems such as anxiety, fear and anger.
  • This paves the path to behavioral problems such as depression, stress-related disorders, irrational fears and compulsive, obsessive disorders.

Neurotransmitters, which are an important component of brain chemistry in humans and dogs, are chemical messengers responsible for carrying, boosting and modulating signals between neurons. There are two types of neurotransmitters:

  1. Excitatory neurotransmitters: These excite the neuron, stimulating it to action. Examples are norepinephrine, epinephrine—aka adrenaline—and cortisol which are fight and flight hormones produced by the adrenal gland.
  2. Inhibitory neurotransmitters: These inhibit the neuron, decreasing its action. Examples include serotonin and GABA.
  3. Excitatory and inhibitory neurotransmitters: These can have both effects depending on the receptors. Examples are acetylcholine and dopamine.

Excitatory Neurotransmitters

Let's take a closer look into these neurotransmitters and their role in canine behavior.


Also known as adrenaline, epinephrine along with norepinephrine and cortisol participate in the flight and fight response by making your dog's heart pump harder, opening the airways, and increasing blood flow to major muscle groups in response to a threat.


Along with epinephrine and cortisol, norepinephrine is a stimulant and participates in the fight-or-flight response, by increasing your dog's heart rate. At the same time, norepinephrine is also a mood enhancer which explains why along with serotonin, norepinephrine has a positive effect on the brain.


This steroid hormone is also released in response to stress along with norepinephrine, epinephrine. When a dog gets into "flight or fight" mode, this chemical is often released and is why it is often referred to as the "stress hormone." Karen Overall of the Center for Neurobiology and Behavior at the University of Pennsylvania found that aggressive dogs displayed an increased level of cortisol in their blood and in a similar fashion did dogs who were fearful and anxious. A study determined that aggressive dogs had 21 units compared to 10 in non-aggressive dogs.

Inhibitory Neurotransmitters


This is a neurotransmitter found in the intestinal tract and central nervous system. lt is thought to be responsible for general feelings of happiness and well-being which is why it is often referred to as the "feel-good" hormone. A study by researchers at Zaragoza University in Spain determined that dogs that were aggressive had lower levels of serotonin in their blood. To be exact, such dogs had 278 units compared to 387 in non-aggressive dogs.

Serotonin, unfortunately, cannot be supplied in the form of a pill or injection. Interestingly though, a class of drugs known as tricyclic antidepressants (TCA) helps slow down the reabsorption rate of the neurotransmitters serotonin and norepinephrine, allowing their levels to rise. A drug belonging to this class is clomipramine.

On the other hand, another class of drugs known as “selective serotonin reuptake inhibitor," often abbreviated as SSRI, helps block the reabsorption of serotonin allowing more serotonin to be available for extended periods of time, explains Certified Applied Animal Behaviorist, Benjamin L. Hart. Drugs belonging to this class include fluoxetine, sertraline and paroxetine.

Note: Buspirone is a serotonin 5-HT Agonist known for activating serotonin receptors, and mimicking the effect of serotonin.


GABA stands for Gamma-aminobutyric acid which is a neurotransmitter responsible for regulating neural excitability. Benzodiazepines help enhance the effect of this neurotransmitter, reducing the firing rate of neurons in the central nervous system.

Excitatory and Inhibitory Neurotransmitters


"Dopamine helps coordinate the dog's motor skills, attention, reinforcement and reaction time and it has an impact on the brain’s mood area where “good feelings” originate" explains dog trainer Nicki Tudge. When neurotransmitters transfer excessive dopamine dogs can become agitated, impulsive and easily reactive, creating an excitatory response. On the other paw, when dopamine levels are reduced the dog becomes under-reactive, creating an inhibitory response.


This neurotransmitter at a cardiac level has an inhibitory effect, which lowers heart rate. However, acetylcholine, may also behave as an excitatory neurotransmitter at the neuromuscular level in skeletal muscles.

What Medications Are Used in Dogs With Behavioral Problems?

The most common class of drugs used in behavior modification are benzodiazepines (BZs), monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), according to the ASPCA. These medications may be prescribed by a veterinarian or board-certified veterinary behaviorist.

  • Acetylpromazine (Acepromazine)
  • Alprazolam (Xanax) BZ
  • Amitriptyline (Elavil) TCA
  • Buspirone (Buspar) serotonin 5-HT Agonist
  • Fluoxetine (Reconcile, Prozac) SSRI
  • Clomipramine (Clomicalm) TCA
  • Diazepam (Valium) BZ
  • Paroxetine (Paxil) SSRI
  • Propranolol (Inderal)
  • Selegiline (Deprenyl, Anipryl) MAOI's
  • Sertaline (Zoloft) SSRI

Do Medications Help Dogs?

While behavior modification alone may help dogs in need and change emotions and brain chemistry, it is also true that in certain severe cases, medications may be needed so to stop the brain from interfering with learning appropriate behavior. Following are some benefits and reasons why medications may be needed in severe cases:

  1. When your dog is in a fight or flight state of mind, he is ready to react and not capable of learning. With medication, your dog will be calmer and has better chances for learning.
  2. Medications may speed up the learning process.
  3. Some medications such as benzodiazepine act quickly if given before exposure.

However, there are also cases where the use of medications, is counter-productive and there are also disadvantages. Here are some of the cons:

  1. There are risks for side effects and paradoxical effects.
  2. As the dog is weaned off the medication there may be relapses.
  3. Most medications are not a quick fix, may need to be taken for a while before effects are seen
  4. Medications should not be used alone; but rather, along with a behavior modification program.

My Experience With Medications vs. Behavior Modification

While I am not a big fan of meds, I think in severe cases and in certain dogs they do help take the edge off (by fixing imbalances in neurotransmitters) so to open up the lines for learning so the dog can cognitively function. And this is a good reason why vets should refer clients to trainers/behavior consultants so the vet can take care of chemical imbalances and the trainer/behavior consultant can handle the behavior modification process. This partnership should help prevent veterinarians from unnecessarily increasing dosages and owners from becoming frustrated because the "meds are not working." And in some cases, the dog may even not need any meds at all, because the trainer/behavior consultant may have alternative approaches/calming aids/methods up their sleeves.

I worked on a case with a behaviorist where the dog had inter-dog aggression and the drugs were needed because according to the behaviorist the dog was reactive no matter the distance. I had my doubts on this though. The fact is, this dog was in a fenced area with the other dog at a distance in a separate fenced area. It seemed to me the drugs were perhaps needed to make him comfortable and work sub-threshold in "THAT setting." If I had this case on my own, I would have been curious to know if in a different setting and with more distance it was possible to find a threshold "oasis" without the need for drugs.

A while back, I was called to work on a case of severe inter-dog aggression where the dog was not walked for over a year in a neighborhood surrounded by fenced dogs. There was little opportunity to find a comfortable threshold distance here because of how the neighborhood was displayed. It took weeks of daily work to get to the point of walking him past the dogs without reacting, but we finally made it. So in my experience, drugs can make the process easier and perhaps even shorten it, but I am not a big fan of them when vets prescribe them because of obvious risks for side effects and the fact that once the dog is weaned off, I have seen relapses (just as in people), whereas with no drugs, the process took longer but the results seemed to be more reliable, at least in my humble opinion.

What do studies say? "Drug therapy is rarely curative by itself and in most cases is only indicated as ancillary therapy in a behavior modification program" according to this abstract.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.


Lin Bauer from CapeTown South Africa on February 06, 2020:

Thank you I will try this next time, having him on a leash until he is calm.

Adrienne Farricelli (author) on February 06, 2020:

Hi Lin,

With anxious dogs like that, treatment generally falls more under behavior modification rather than training. I would prevent him from having direct access to guests to prevent rehearsal of the trouble behavior (nipping, acting anxious) and would suggest keeping him distant with a leash (to keep him under threshold) and gradually work on changing his emotions towards people coming into the house. Because of the importance of correct implementation of behavior modification and safety, it's important to enlist the help of a dog behavior professional using force-free behavior modification. Severe cases of anxiety may require meds prescribed by the vet. This is just an example of the type of work I did with a dog anxious about a person entering the home.

Lin Bauer from CapeTown South Africa on February 05, 2020:

I have a very anxious 2 yrs old GSD he gets very anxious when people come to my house, he is then unable to control himself and starts to nip,after a nip he increases his distance & is very submissive. He is otherwise very obedient we do go to training in a group every week where he is the "perfect" dog, he gets anxious when there is a lot of excitement or sudden movement. He was rescued at 6wks, his mother passed away at this time from abuse & neglect, I got him at 3mnths. We immediately started puppy training. He is very protective of my two granddaughters. I have a 15yr cocker spaniel who he adores but every now and then he seem to "snap" and snaps at her grabbing her by the ears, he has never hurt her or broken skin, immediately afterwards he goes into a submissive position & goes to lick her face. I also have a 4yrs Belgium Mallinois, & 1yr Swiss Shepherd, he has not behaved like that towards them, he does get over excited when he plays with the Swiss & hurts her she she then yelps & walks a way, or when I notice the play is escalating I will say "gently" he then backs off & continues play more calmly. He is a high energy dog, we walk for 1hr 5/wk, 2hrs beach walk x1/wk & obedience class with play afterwards x1/wk. He was neutered at 9 Mnths, he does not do resources in his food but does guard my granddaughter when he is in the room with her, my daughter the other day opened the bedroom door & walked in without identifying herself, he snapped & barked and nipped her on the leg.How can I do to help my dog who is gentle except when these episodes happen.

Alexandra Bassett on May 26, 2019:

Great article. Very thorough overview. Thank you!

Adrienne Farricelli (author) on August 23, 2018:

John, before thinking about chemical imbalance, it may be worthy considering other dyanamics taking place such as fear aggression or resource guarding. Please consult with a professional to help determine the underlying dynamics and triggers.

John Pryce on August 20, 2018:

I have a Jack Russell dog that sume time's tries to bite dogs or people can she have chemical imbalance

annerivendell from Dublin, Ireland on September 17, 2012:

Another great hub. What an interesting area too! Voted up.

Adrienne Farricelli (author) on September 16, 2012:

Nat Amaral, I agree dogs should get an individualized treatment plan since they all respond differently to treatment. The one size fits all definitely does not apply here.

Adrienne Farricelli (author) on September 16, 2012:

Thanks Mary, I am studying to further continue my education (this time specializing in getting a canine psychology degree), so you will see more and more articles tackling dog behavior for some time!

Nat Amaral from BC Canada on September 16, 2012:

I love this hub. Yes, I think there should be treatment for the aggressive dog behavior because of some past experiences (bitten by 2 different dogs on 2 different occasions), but that should be done with some caution. Every dog will respond to it differently, and in some cases, it won't always be good.

Mary Hyatt from Florida on September 16, 2012:

As always, you have written a very informative Hub. You are certainly an expert in canines and their behaviors. I've never had an aggressive dog, thank goodness.

My Miniature Schnauzer is an easy going dog for the most part.

I voted this Hub UP, etc. and I will share this good info.

Adrienne Farricelli (author) on September 16, 2012:

Thank you. Studies have shown that diet can have a calming effect on dogs. One study suggests that tryptophan helps dogs suffering from aggression and hyperactivity. This makes sense, since trytophan is know for causing sleepiness in humans after drinking milk or eating chicken/turkey along with a carbohydrate snack.

Larry Fields from Northern California on September 16, 2012:

Hi Alexadry. Loved your hub.

I used to take my neighbor's family's Border Collie mix on day hikes. I found that a home-made 'treat', consisting mainly of Carob powder and butter-flavored Crisco, had a slight calming effect on Gurr. When we stopped to eat lunch, he would get that for 'dessert', after a handful of his regular kibble. Milk Bone dog biscuits had the opposite effect. Go figure.

Voted up and interesting.