Meeting Abstract

P1.127  Saturday, Jan. 4 15:30  Acute Restraint Stress Decreases Gonadotropin-Inhibitory Hormone Immunoreactivity in the Zebra Finch Hypothalamus ERNST, DFK*; LYNN, SE; BENTLEY, GE; Univ. of California, Berkeley; College of Wooster; Univ. of California, Berkeley dfkernst@berkeley.edu

Gonadotropin-inhibitory hormone (GnIH) acts to inhibit reproduction at all levels of the hypothalamo-pituitary-gonad (HPG) axis. GnIH in the hypothalamus increases with acute stress in some birds and mammals, thus representing a mechanism by which stress can inhibit reproduction. The zebra finch is an opportunistic breeder for which timing of breeding is closely associated with unpredictable environmental cues. Thus, the zebra finch GnIH system may be more sensitive to stress than that of seasonal and/or continuous breeders. To test this, we collected tissues from males and females in mixed-sex aviaries immediately after capture or following 60 min of restraint. As expected, restraint significantly increased plasma corticosterone in males and females. Contrary to studies on other species, immunocytochemistry for GnIH revealed significantly fewer GnIH immunoreactive (-ir) cell bodies in the stressed birds. There was no sex difference in GnIH cell number in either treatment or control animals. Our data indicate that the GnIH system of zebra finches responds strongly to acute stress, but by a reduction of GnIH peptide, rather than the predicted increase. Further research will determine whether the stress-induced reduction of GnIH-ir cell bodies is a consequence of increased GnIH release or decreased gene expression in response to restraint. Regardless, our data suggest that although GnIH responsiveness to stress appears to be conserved, the directionality of response does not. Variation in the GnIH response to stress among species might be the result of ecological adaptations or species differences in GnIH function, though additional research is necessary to draw firm conclusions.