Dehydroepiandrosterone administration reverses the inhibitory influence of aging on gonadotrophin-releasing hormone gene expression in the male and female rat brain
Résumé
Dehydroepiandrosterone (DHEA) has been shown to exert a beneficial influence on some aging-associated deficits in rodents. It is well documented that in the rat, aging is associated with a decline in reproductive functions. In order to evaluate the effect of DHEA on GnRH gene expression in aged animals, we have studied the effect of 2.5-d administration of DHEA to young (50-54 d of age) and aged (18 mo of age) rats of both sexes. In the young males, DHEA induced an 18% reduction in the hybridization signal. In the aged animals, the mRNA levels were 10% lower than those observed in the young rats. DHEA completely restored the mRNA levels when compared to those detected in young male animals. In the young female, DHEA produced a 11% increase in GnRH mRNA, whereas, in the aged animals, hybridization signal was decreased by 28%. DHEA administration to aged females induced a 33% increase in the amount of mRNA, thus completely reversing the influence of aging. These results indicate that the decrease in GnRH gene expression which is likely involved in the loss of reproductive functions in aged rats can be totally reversed by a short term administration of DHEA which restored the GnRH neuronal activity. They also suggest that DHEA might play a role in the prevention and/or improvement of some deficits associated with aging through stimulation of GnRH biosynthesis.