Effects of Stroking on Salivary Oxytocin and Cortisol in Guide Dogs: Preliminary Results

SIMPLE SUMMARY: Oxytocin, a nonapeptide hormone produced by the hypothalamus and secreted by the pituitary gland, plays a peripheral role during labor, birth, and nursing. Since this role is well known nowadays, scientific interest in this hormone has shifted from its peripheral functions to its central functions, such as the onset of parental care, the regulation of social bonding, and modulation of the emotional state. For this final reason, this study intended to investigate the possible variations of salivary oxytocin induced by two different conditions: a positive condition (5 min of human–dog interaction) and a negative condition (5 min of isolation). Because oxytocin function is known to be affected by stress, salivary cortisol concentration was determined after both conditions and a stress–behavior assessment during the isolation phase was performed to further assess signs of distress. A significant increase in salivary oxytocin was observed only during the positive condition and, although no signs of distress were observed during the isolation phase, a correlation between the variations of salivary oxytocin and cortisol concentrations was found. These findings highlight the possibility of measuring the potential impact of stress on the oxytocinergic system during behavioral tests. ABSTRACT: This pilot study aimed at investigating how salivary oxytocin levels are affected by human interaction and isolation in eight guide dogs (six Labrador retrievers and two golden retrievers; four males and four females, 21.87 ± 1.36 months old) just before assignment to the blind person. Each dog engaged, at one-week intervals, in a positive (5 min of affiliative interaction with their trainer) and a negative (5 min of isolation) condition. Saliva samples used for Enzyme Immunoassay (EIA) quantification of salivary oxytocin were collected before and immediately after both experimental conditions. In order to assess potential hypothalamic pituitary adrenal (HPA) axis activation that could have affected oxytocin levels, saliva samples were collected 15 min after both experimental conditions for EIA quantification of salivary cortisol and a behavioral assessment was performed during the negative condition. The results were compared using the Wilcoxon test (p < 0.05). Oxytocin concentrations showed a statistically significant increase after the positive interaction (p = 0.036) and no difference after the negative one (p = 0.779). Moreover, no difference (p = 0.263) was found between the cortisol concentrations after each experimental condition and no signs of distress were observed during the isolation phase. These preliminary findings support the hypothesis that stroking dogs has positive effects on their emotional state independently of hypothalamic pituitary adrenal axis activation.