65.1 Saturday, Jan. 5 Endocannabinoid regulation of glucocorticoids â€" its for the birds DICKENS, M.J.*; BENTLEY, G.E.; Univ. of California, Berkeley; Univ. of California, Berkeley email@example.com
Endocrine regulation of corticosterone (CORT) release during the stress response is well described in wild birds. Neural mechanisms impinging upon this endocrine system and regulating it seasonally are less well defined. Typically, the CORT response is down-regulated during molt in seasonally-breeding birds, yet underlying mechanisms of this phenomenon are unclear. The endocannabinoid (eCB) system, a lipid-signaling pathway, may act as a central influence upon baseline and stress-induced CORT release in a seasonal manner. Here, we demonstrate a role for the eCB system in regulating the changing CORT response between breeding and molting conditions. First, using two groups of male European starlings, we targeted action at the eCB neural receptor (CB1) by injecting a CB1 specific antagonist, AM251, and measured subsequent CORT concentrations. CORT significantly increased with injection of the antagonist regardless of observed seasonal changes in CORT concentrations. These data suggest that blockade of the eCB signal releases the CORT response. Notably, the antagonist resulted in greater CORT increases in breeding males. Thus, the eCB system likely acts to inhibit the CORT response, an effect which may be stronger in breeding versus molting birds. Using in situ hybridization, we confirmed the presence of CB1 receptor expression in the paraventricular nucleus (PVN) of the hypothalamus, hippocampus (HP) and nucleus taeniae amygdala (TnA), sites known for their role in eCB-mediated CORT regulation in mammals. qPCR data suggest that the highest degree of CB1 expression in these nuclei occurs in the TnA followed by the HP and then PVN. Overall, these findings indicate a previously unidentified role for the endocannabinoid system in the regulation of the avian stress response.