It turns out that your dog's brain isn't all that different from your own. Dr. Nicholas Dodman, director of the behavior clinic at Tufts Cummings School of Veterinary Medicine, North Grafton, MA, has been studying compulsive behaviors in dogs, horses and cats for decades. And for years he's been encouraging using these animal models to help understand what's going on with people with obsessive-compulsive disorders (OCD). However, he's had to wait for both popular scientific culture and gene identifying scientific techniques to catch up with his notions.
Today, science has finally met up with Dodman.
The window first opened in 1991 with work published in the American Animal Hospital Association Journal and the Archives of General Psychology about repetitive licking in dogs. "It turned out that it (the repetitive licking) was a dead ringer for human OCD," Dodman says.
Dodman has been waiting to prove his theory -- that while compulsive behavior may be expressed differently in dogs than in people, such behavior is all pretty much the same. "The only differences are in the ways compulsive behaviors are expressed as a result of species and breed," Dodman explains.
For example, Border Collies, an intense herding breed, generally express their breed-specific compulsive behavior by chasing lights. Bull Terriers convey compulsion consistent with their predator lineage by chasing their own tails. Dobermans don't suck their thumbs (maybe they would if they had thumbs) but do express their breed-specific compulsive behavior by sucking on their own flanks, and sometimes sucking on blankets.
Interestingly, thumb-sucking can be a compulsive disorder in people. Other examples of OCDs include non-stop double-checking to ensure appliances are turned off, compulsive hand-washing, even self-mutilation like pulling out hair.
Dodman says he believes the genetic explanation for compulsive disorders is all pretty much the same, whether it's a horse that cribs (grabs a solid object, such as a stall door or fence rail with its incisors, arches its neck and sucks in air), a cat who sucks on fabric, a Doberman who sucks on his flank, or a person who compulsively sucks his thumb.
That's where Dr. Edward Ginns, director of Medical Genetics and Molecular Diagnostics Laboratory the University of Massachusetts Medical School, Worcester, comes in. Neurotransmitters in human and canine brains are identical, and overall dog and human brains are pretty much the same. So, it makes sense -- at least to a growing number of scientists -- that studying canines can actually lead to answers about human health. Ginns sought to study dogs for another reason. as well. "My approach has been to study isolated populations," he says. "And that's what dog breeds are."
So, the UMass group harvested Doberman DNA from 94 flank-sucking and/or blanket-sucking dogs. Then Ginns and his team compared that DNA to the DNA of 73 "normal" Dobermans. "And there it was, bingo," says Dodman, the author of several top-selling pet books.
"Bingo" is a specific spot on chromosome 7 which contains a gene called Neuronal cadherin-2, or CDH2. This spot consistently appeared at a far higher frequency in the compulsive dogs.
At first, this finding may not seem significant. But consider the flurry of activity happening as a result. For starters, scientists at the National Institutes of Health are now sequencing the same gene in people to determine whether it's linked to human OCD.
Ginns points out that more work needs to be done to formalize the specific alteration in chromosome 7, but the outcome for dogs might be a new class of drugs to more efficiently target compulsive behaviors in dogs, and also ultimately for people. Right now, SSRI drugs (like Prozac) are used to treat compulsive behaviors in dogs with mixed success. The odds for success are far greater with behavior modification.
The genetic finding offers proof, for the first time, that at least for dogs, there's likely a genetic predisposition for compulsive behaviors. Still, these behaviors only seem to occur in dogs, cats and horses with the right set of environmental stressors, which is also true for people. However, since no one completely understands the relationship between genetics and these stressors, this work could be a start.
For sure, if the gene is confirmed in Dobermans, breeders in the future may be able to use a simple blood test to determine if the genetic defect indicating a higher risk for compulsive disorders is present before breeding. Careful breeding could lessen the chances of the problem occurring in Dobermans, and potentially other dog breeds, even other species.
Dodman does have DNA samples collected for other breeds; Bull Terriers will be investigated next. Dodman says he guesses the same gene alteration may be present in other breeds, and even in people.
"I'm confident that we're on our way to a better understanding of the expression of compulsive behaviors, and that will help dogs and also help people," Ginns says.
(Steve Dale welcomes questions/comments from readers. Although he can't answer all of them individually, he'll answer those of general interest in his column. Write to Steve at Tribune Media Services, 2225 Kenmore Ave., Suite 114, Buffalo, NY 14207. Send e-mail to PETWORLD(at)STEVE DALE.TV. Include your name, city and state. Steve's website is www.stevedalepetworld.com; he also hosts the nationally syndicated "Steve Dale's Pet World" and "The Pet Minute." He's also a contributing editor to USA Weekend.
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