157 | A preliminary study on the interplay between serum neurotransmitter levels and the behavioral phenotype of Canis familiaris

Federica Arrigo¹, Raffaella Cocco², Claudia Giannetto¹, Giuseppe Piccione¹, Alberto Cesarani^3|4, Giuseppe Pulina³, Sara Sechi², Francesca Arfuso¹ | ¹Department of Veterinary Sciences, University of Messina, Messina, Italy; ²Department of Veterinary Medicine, University of Sassari, Italy; ³Department of Agriculture, University of Sassari, Italy; ⁴Department of Animal and Dairy Science, University of Georgia, Athens, GA, USA.

Domestication and selective breeding have profoundly shaped the behavioral phenotypes of domestic dogs, resulting in marked differences among breeds in temperament, motivation and stress reactivity. These traits are closely regulated by neuroendocrine mediators, including neurotransmitters involved in mood regulation, reward processing and stress responses (1,2). The present study aimed to investigate the possible relationship between the blood levels of selected neurotransmitters such as serotonin, dopamine, norepinephrine, prolactin and beta-endorphins and the behavioral phenotypes in different dog breeds. Clinically healthy dogs belonging to several breeds were enrolled and underwent behavioral assessment through owner questionnaires, ethograms and standardized behavioral tests. Blood samples were collected under standardized conditions and analyzed using validated immunoassays. Serotonin and dopamine concentrations were below the reference ranges in 62% and 70% of dogs, respectively, whereas beta-endorphin levels exceeded reference values in 49% of the study population; norepinephrine concentrations remained within physiological ranges in 68% of dogs, with significant positive correlations observed among serotonin, dopamine and norepinephrine (p < 0.001).The results showed that reduced circulating levels of serotonin and dopamine were observed, suggesting alterat ions in mood-related and reward-related neurochemical pathways. Elevated beta-endorphin concentrations were commonly detected, indicating activation of stress-related adaptive mechanisms, while norepinephrine values generally remained within physiological ranges. The neurotransmitters investigated showed coherent patterns of interaction, reflecting the close functional integration between reward, mood and stress regulation systems. The breed significantly affected the values of beta-endorphins and dopamine (p < 0.001). Specifically, dogs belonging to Crossbreed showed higher beta-endorphins values (p < 0.001) than dogs belonging to Labrador, German Shepherd, Pit Bull and Fonni’s dog breeds. Labrador showed higher beta-endorphins, dopamine values than Crossbreed, German Shepherd, Pit Bull and Fonni’s dog (p < 0.001). Altered neurochemical patterns were often associated with behavioral manifestations such as hyperreactivity, aggression, anxiety and compulsive behaviors, particularly in dogs whose living conditions or activities did not adequately satisfy breed-specific motivational needs. Conversely, dogs engaged in structured working or research activities displayed more balanced neuroendocrine profiles and fewer behavioral alterations. In conclusion, the evaluation of circulating neurotransmitters and stress-related hormones represents a valuable approach for improving the understanding of breed-specific behavioral phenotypes. This integrative assessment may support breeders, trainers and veterinarians in selecting suitable dogs for specific tasks and in promoting animal welfare through management strategies that respect innate behavioral predispositions.