The Role of Prolactin as a Potential Biomarker of Stress in the Domestic Dog

This research documents significant contributions to physiology and ethology for the domestic dog, whose interest is growing among society. Considering that prolactin has been reported to be a remarkable index of stress response, both acute and chronic, in several species, this research aimed to: a) Investigate the possibility of using a commercial ELISA kit for measuring canine prolactin in blood for the quantification of canine prolactin in saliva, due to the lower invasiveness of saliva collection. A validation protocol was done, and the possible correlation between prolactin concentration in saliva and plasma was assessed. Results concluded that saliva was not an adequate matrix for the kit to reliably quantify canine prolactin. b) Investigate the possibility of using a commercial ELISA kit for measuring cortisol in blood for the quantification of canine hair cortisol. Results were satisfactory. c) Investigate the role of prolactin in the stress response through an extensive analysis on sheltered dogs. Serum cortisol and prolactin, hair cortisol, and behavioural and demographic variables were considered. Results were generally in agreement with previous studies and expected relationships. Although other authors already established the possibility that prolactin may be a reliable marker of acute stress, our results showed that: (a) Prolactin might be a reliable biomarker of chronic stress; and (b) Prolactin and cortisol could be different alternative ways to respond to stress.