Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 53, Issue 3 B191-B195, Copyright © 1998 by The Gerontological Society of America
Alterations in the opioid control of LHRH release from hypothalami isolated from aged male rats
SJ Nazian, CS Landon and JR Dietz
Department of Physiology and Biophysics, College of Medicine, University of South Florida, Tampa, USA. snazian@com1.med.usf.edu
Several lines of evidence have suggested that the opioid control of
gonadotropin secretion in the male rat is altered with aging. Because
neural control of gonadotropins is mediated through luteinizing hormone
releasing hormone (LHRH) secreting neurons, we examined the postulated
changes in the opioid control of gonadotropins more directly by studying
isolated hypothalamic fragments in vitro. Hypothalami from young (75-90
days) and old (18-20 months) males were examined for their ability to
release LHRH when incubated with increasing doses of naloxone in a
semi-static culture system. Serum concentrations of testosterone and
luteinizing hormone (LH) in the donor animals were both significantly lower
in old male rats compared with young males. Basal secretion of LHRH was
similar in both age groups. Two-way repeated measures ANOVA indicated that
naloxone stimulated a significant dose-dependent increase in the release of
LHRH into the media. ANOVA also indicated a significant effect of age. We
conclude that the changes in the endogenous opioid systems reported to
occur with aging are, in fact, linked to differences in LHRH secretion and
thus to differences in the dynamic relationship between testosterone and LH
in older male rats.
