The Role of the Avian Vasotocin 1a (V1a) and V1b Receptors in the Neuroendocrine Regulation of Stress

The avian vasotocin receptors type 4 (VT4R) and 2 (VT2R) are homologous to the mammalian vasopressin receptors V1aR and V1bR, respectively.  With respect to the neuroendocrine regulation of stress in birds, it has been shown following acute psychological stress, that the avian V1aR and V1bR and corticotropin releasing hormone 1 receptor (CRH-R1) and 2 receptor (CRH-R2) displayed significantly different gene expression levels compared to controls.  Brain distribution of the avian V1aR showed its presence not only in neurons but also in glia, particularly in all ten circumventricular organs.  Dense V1aR immunoreactivity (ir) was found in the organum vasculosum of the lamina terminalis (OVLT) and sub-fornical organ (SFO).  In birds subjected to a physical stressor, intraperitoneal injection of sodium chloride, significantly increased V1aR gene expression occurred in the SFO as well as the OVLT compared to controls.  It was also shown that the dorsal portion of the nucleus of the hippocampal commissure (nHpC) contains a population of CRH neurons in close vicinity to V1aR ir glial cells.  Cells within the dorsal nHpC likewise showed significant activation following acute stress based upon Fos protein immunoreactivity.  Functional data suggest that (1) both the avian V1aR and V1bR are involved in the neuroendocrine regulation of psychological stress, (2) the avian SFO and OVLT containing V1aR-ir glia appear to play a role in physical stress and (3) CRH neurons within the dorsal region of the nHpC are involved in the stress response.  Supported in part by grants from NSF (#O842937) and the Arkansas Biosciences Institute.