Fos-induction in gonadotropin-releasing hormone neurons receiving vasoactive intestinal polypeptide innervation is reduced in middle-aged female rats

K. Krajnak, K. L. Rosewell, P. M. Wise

Research output: Contribution to journalArticlepeer-review

Abstract

A hallmark of reproductive aging in rats is a delay in the initiation and peak, and a decrease in the amplitude, of both proestrous and steroid-induced surges of LH and a decrease in the number of GnRH neurons that express Fos during the surge. The altered timing of the LH surge and the decline in Fos expression in GnRH neurons may be due to changes in the rhythmic expression of vasoactive intestinal polypeptide (VIP), a neuropeptide that carries time-of-day information from the circadian pacemaker, located in the suprachiasmatic nuclei (SCN), to GnRH neurons. The goals of our study were to determine if aging alters 1) the innervation of GnRH neurons by VIP and 2) the ability of VIP to activate GnRH neurons by examining the effects of aging on the number of GnRH neurons apposed by VIP fibers and the number of GnRH neurons that receive VIP input that express Fos. Immunocytochemistry for GnRH and VIP; or GnRH, VIP, and Fos was performed on tissue sections collected from young (2-4 mo), regularly cycling females and middle-aged (10-12 mo) females in constant estrus. The number of GnRH neurons, GnRH neurons apposed by VIP fibers, and GnRH neurons that express Fos and apposed by VIP fibers were counted in both age groups. Our results clearly demonstrate that aging does not alter the number of GnRH neurons that receive VIP innervation. However, the number of GnRH neurons that receive VIP innervation and coexpress Fos decreases significantly. We conclude that the age-related delay in the timing of the LH surge is not due to a change in VIP innervation of GnRH neurons, but instead may result from a decreased sensitivity of GnRH neurons to VIP input.

Original languageEnglish (US)
Pages (from-to)1160-1164
Number of pages5
JournalBiology of reproduction
Volume64
Issue number4
DOIs
StatePublished - 2001
Externally publishedYes

Keywords

  • Aging
  • Circadian rhythm
  • Gonadotropin-releasing hormone
  • Hypothalamus
  • Neuropeptides
  • Suprachiasmatic nucleus

ASJC Scopus subject areas

  • Reproductive Medicine
  • Cell Biology

Fingerprint

Dive into the research topics of 'Fos-induction in gonadotropin-releasing hormone neurons receiving vasoactive intestinal polypeptide innervation is reduced in middle-aged female rats'. Together they form a unique fingerprint.

Cite this