An exploratory study about the association between serum serotonin concentrations and canine-human social interactions in shelter dogs (Canis familiaris)

The monoamine neurotransmitter serotonin (5-hydroxytryptamine [5-HT]) is involved in neuronal excitability, regulates mood and cognition, and is implicated in the regulation of a wide range of social behavior. Understanding its role in social behavior would be useful in understanding and improving human-animal interactions, in particular, the human-dog interaction. Examination of canine social behavior is crucial for screening shelter dogs to be placed for adoption or for identifying dogs that need behavioral intervention. Behavior problems in dogs can arise because of long-term stays in shelters. The aim of this study was to determine whether serum 5-HT is related to behavioral responses in shelter dogs. Fourteen mixed-breed castrated male dogs, with no signs of aggressive behavior toward humans, were selected for exploring the relationship between 5-HT and social behavior in dogs. These dogs were individually observed by an operator during a sociability toward humans test, and their behavioral responses toward the operator were evaluated using a simple test constituted by 7 episodes: Operator approaches the door of the pen, coaxes the dog, attempts to sit the dog and ask for its forelimb, attempts to put a collar on the dog, walks with the dog on a leash, throws a tennis ball against a wall and plays alone, and throws the tennis ball and invites the dog to play with him once. Each episode was scored from 2 to 8, with low scores representing the most fearful dogs. Blood samples were drawn from the cephalic vein during routine health checks, and some serum was retained for 5-HT analysis. A weak linear correlation between the behavioral scores from operator-dog interactions and 5-HT levels (r2 = 0.31, P < 0.05) was found. According to these preliminary data, markers of the serotoninergic system could be related to the sociability of dogs toward humans.