Meeting Abstract

56.6  Tuesday, Jan. 5  A functional neuropeptide system in avian gonads MCGUIRE, Nicolette L.*; KANGAS, Kristina; BENTLEY, George E.; Univ of California, Berkeley; Univ of California, Berkeley; Univ of California, Berkeley nicolette@berkeley.edu

Several hormone systems identified in the vertebrate brain and classified as neurohormones are synthesized in and have a localized action on the gonads. The expression and action of GnIH (gonadotropin inhibitory hormone) has been characterized in the hypothalamus and pituitary, respectively. The action of this neurohormone is to inhibit the synthesis and secretion of luteinizing hormone and follicle stimulating hormone from the pituitary. Despite knowledge of the presence of transcripts and mature forms of GnIH and GnIH receptor (GnIHR) in vertebrate gonads, a functional role for the gonadal GnIH system has remained unclear. The nature of this system in the gonads may be very different from its more characterized counterpart in the central nervous system. Here we present several lines of evidence for the expression and action of GnIH and GnIHR in the testis of house sparrow (Passer domesticus) and European starling (Sturnus vulgaris). Using coamplification RT-PCR with an endogenous control (β-actin), we show that the testes of photorefractory, non-breeding, European starlings produce significantly more mRNA for GnIH and GnIHR than the testes of photostimulated, breeding, starlings. Using house sparrow testis culture and EIA, we demonstrate that GnIH significantly reduces testosterone production. These data indicate a role for gonadal GnIH in maintenance of gonadal regression on a seasonal basis and rapid suppression of gonadal steroid release within the breeding season.