Immunohistochemical characterization of chicken pituitary cells containing the vasotocin VT2 receptor

Abstract

Research in mammals has demonstrated a variety of regulatory effects of vasopressin and oxytocin on endocrine functions of the anterior pituitary gland. Less evidence is available regarding the hypophysiotropic action of arginine vasotocin (AVT) comprising vasopressic and oxytocic activities in birds. Some hypophysiotropic effects of AVT may result from its interactions with brain circuits controlling pituitary functions, whereas others are caused by its direct affect on pituitary cells. Use of an antiserum to the vasotocin receptor VT2 (VT2R) has revealed numerous immunoreactive cells in the anterior pituitary gland of the chicken. The objective of the present study has been to identify endocrine phenotypes of chicken pituitary cells containing VT2R by means of immunohistochemical labeling. VT2R immunoreactivity has been found in all cells immunoreactive for adrenocorticotropin and alpha-melanotropin. Approximately 10% of labeled lactotropes are also immunoreactive for VT2R and lie around the anatomical boundary dividing the cephalic and caudal lobes. In both corticotropes/melanotropes and lactotropes, immunoreactive VT2R is present in a narrow layer outlining cell bodies. Immunoreactive VT2R is not found in gonadotropes, thyrotropes, or somatotropes. These results provide evidence for the important role of VT2Rs in mediating effects of AVT on endocrine secretion from corticotropes and, partially, from lactotropes.

Distribution of the Vasotocin Subtype Four Receptor (VT4R) in the Anterior Pituitary Gland of the Chicken, Gallus gallus, and its Possible Role in the Avian Stress Response

“…The VT4R shown to be present in the cephalic lobe (Fig. a,b ), similar to our past data addressing the distribution of the VT2R , provides further evidence for a functional division of the avian anterior pituitary. The AVT and CRH neural projections to the rostral portion of median eminence would transport the neuropeptides (AVT and CRH) to the anterior portal capillary system, thereby influencing pituitary cells present in the cephalic lobe .…”

Localization of three types of arginine vasotocin receptors in the brain and pituitary of the newt Cynops pyrrhogaster

“…The expression of the VT2 receptor in a small population of lactotropes in the chicken anterior pituitary has recently been reported (Jurkevich et al 2008). Although the physiological significance of this effect is open to debate, AVT stimulates the release of prolactin from cultured anterior pituitary cells of the turkey (Proudman and Opel 1988;el Halawani et al 1992).…”

“…In mammalian species, AVP V1b receptor expression occurs in corticotropes (Lolait et al 1995;Hernando et al 2001), and the role of this receptor in mediating vasopressin-induced ACTH release from the anterior pituitary has been confirmed (Antoni 1993). The V1b-type receptor is also expressed mainly in corticotropes in avian species (Jurkevich et al 2005(Jurkevich et al , 2008. In mammals, corticotropin-releasing factor (CRF) is a major stimulator of ACTH release (Vale et al 1981).…”

Brain Arginine Vasotocin Immunoreactivity Differs between Urban and Desert Curve-Billed Thrashers, <i>Toxostoma curvirostre</i>: Relationships with Territoriality and Stress Physiology

“…In birds, both central and peripheral AVT administration increase plasma CORT [Romero and Rich, 2007;Jurkevich et al, 2008;Madison et al, 2008]. This increase is greater in urban than in desert Relationship between AVT-ir at the ME and plasma osmolality in both urban and desert thrashers.…”