Sex differences in plasma corticosterone release in undisturbed chickens (Gallus gallus) in response to arginine vasotocin and corticotropin releasing hormone

In birds, two neuropeptides, corticotropin releasing hormone (CRH) and arginine vasotocin (AVT), are major regulators of the hypothalamo-pituitary-adrenal axis (HPA) during the stress response. In birds, however, the relative efficacy of CRH and AVT to stimulate the HPA axis in males and females remains unknown. The purpose of this study was to determine the time course of CORT release following central CRH and AVT administration to male and female chickens. Chickens were fitted with a stainless steel cannula surgically implanted in the lateral ventricle and a catheter chronically inserted in the jugular vein. Birds were housed individually in cages behind a one-way glass partition and unnecessary noise was avoided during the sampling period. Each bird received a single 5.0 μl intracerebroventricular (ICV) injection of either saline (SAL), AVT (10 and 100 pmol), or CRH (10 and 100 pmol). Blood was sampled remotely every 15 min for 2 h and plasma CORT was determined by radioimmunoassay. There was a significant increase in plasma CORT concentration in males injected with 100 pmol AVT beginning at 15 min post-injection through 2 h compared with SAL injected birds. In males, injection of 100 pmol CRH was significantly more effective in releasing CORT compared to an equal molar concentration of AVT or SAL. In females, ICV injection of 100 pmol AVT induced moderate increase in CORT levels. In contrast, 100 pmol CRH significantly increased plasma CORT compared to SAL injected controls but the CORT response was nearly 50% less than that obtained in males.