Immunohistochemical localization of chicken gonadotropin‐releasing hormones I and II (cGnRH I and II) in turkey hen brain

Abstract

The distribution of cells and fibers immunoreactive (ir) for either chicken gonadotropin-releasing hormone I (cGnRH I; [Gln8]GnRH) or II ([His5,Trp7,Tyr8]GnRH) was determined in brains of turkey hens to reveal whether these peptides occur in separate neuronal systems. ir-cGnRH I cells were located: along the medial aspect of the ventriculus lateralis, nucleus accumbens, and bed nucleus of the stria terminalis; ventral to the tractus septomesencephalicus and extending medially to the third ventricle, and caudally into the lateral hypothalamic area; and in a diffuse band extending from the nucleus preopticus medialis to the nucleus dorsomedialis anterior thalami. cGnRH I fibers were evident in these areas in addition to the hippocampus, nucleus subhabenularis medialis, nucleus ventromedialis hypothalami, and median eminence. Two groups of ir-cGnRH II cells were observed: a magnocellular group lying between the substantia grisea centralis and the nucleus ruber; and a parvicellular group lying medial to the nucleus of the basal optic root and extending into the lateral hypothalamic area. ir-cGnRH II fibers were prominent in limbic structures (cortex piriformis, lateral to nucleus taeniae, hippocampus); olfactory areas (tuberculum olfactorium, nucleus subhabenularis lateralis, nucleus septalis lateralis); areas that in other avian species have steroid-concentrating cells or receptors (medial edge of lobus parolfactorius, nucleus septalis medialis, nucleus periventricularis magnocellularis, nucleus dorsomedialis posterior thalami); and areas containing ir-GnRH I cells or fibers but not in median eminence. These results suggest that cGnRH I and II occur in separate neuronal systems and that cGnRH II does not directly promote pituitary gonadotropin secretion.

Sex differences in the response to environmental cues regulating seasonal reproduction in birds

“…However, based on its anatomical distribution, cGnRH-I appears to be the primary regulator of gonadotrophin secretion in birds (e.g. Millam et al 1993;see Ball & Hahn (1997) for a review). This system exhibits remarkable seasonal plasticity in several avian species in that there is a marked decline in the expression of the peptide after the onset of photorefractoriness (see Ball & Hahn (1997), Dawson et al (2001), MacDougall-Shackleton et al (2005) for reviews) and even a seasonal decline in the release of gonadal steroids in response to GnRH stimulation of the pituitary-gonadal axis during the breeding season (Jawor et al 2006).…”

Identification, localization, and regulation of passerine GnRH-I messenger RNA

“…The main population of cGnRH-I-ir cell bodies in the avian brain is a bilateral cluster in the pre-optic area (POA) that extends from the anterior commissure to the supracommissural division of the organum vasculosum of the lamina terminalis. Cell bodies immunoreactive for cGnRH-II are situated in the midbrain (Juss et al 1992, Millam et al 1993. GnRH-I immunoreactive neurons typically project to the median eminence, allowing regulation of pituitary gonadotropin release.…”

Prior Experience with Photostimulation Enhances Photo-Induced Reproductive Response in Female House Finches

“…While GnRH-ir cell bodies were not seen in both sections from some 291 birds, GnRH-ir fibers were always present. Although the GnRH antibody recognizes 292 both GnRH-I and -II, only GnRH-I and not GnRH-II cell bodies are present in the septo-293 preoptic area (Millam et al, 1993;van Gils et al, 1993;Sharp, 2005). Previous studies 294 have found that this region is innervated by central photoreceptors (Saldanha et al, 295 1994(Saldanha et al, 295 , 2001) and responds to photostimulation with increased fos-like immunoreactivity 296 Follett, 1995, 1997;Millam et al, 2003) Mauro et al, 1989Mauro et al, , 1992.…”