Different responses of gonadotropin-releasing hormone (GnRH) release to glutamate receptor agonists during aging.

GnRH release from hypothalamic explants from young and aged male Wistar-Kyoto rats was evaluated following stimulation with glutamate receptor agonists. Glutamate stimulated GnRH release to a similar extent in hypothalami from young and old animals, whereas N-methyl-D-Aspartate (NMDA) and kainate appeared more efficacious in young and old rats, respectively. Old rats were unable to respond to a maximal stimulating concentration of glutamate when they had been previously exposed to a challenge with the same agent. These results demonstrate that responsiveness to glutamate receptor agonists changes during aging, suggesting the involvement of distinct glutamate receptors in the control of GnRH release during different phases of lifespan.