Further observations on the effects of neonatally administered monosodium glutamate on the reproductive axis of hamsters

Abstract

The purpose of the present investigation was to study the alterations in the reproductive neuroendocrine axis of adult male and female hamsters given saline or 8 mg MSG/g BW on both Day 7 and Day 8 of the neonatal period. As adults all female hamsters given monosodium glutamate (MSG) were acyclic, had significantly lower uterine and pituitary weights and significantly lower levels of FSH in the plasma and anterior pituitary glands. Histological examination of the ovaries revealed only small follicles. In addition only 7.3% of the neurons in the arcuate nucleus of the hypothalamus (ARC) were morphologically intact. The histochemical activity of the enzyme 3-β-hydroxysteroid dehydrogenase (HSD) in the interstitial cells of the ovary was comparable to that found in control tissue, but all the cells were hypertrophied. All adult male hamsters given MSG on Day 7 and Day 8 of the neonatal period had significantly lower testicular, seminal vesicle and pituitary weights as well as lower FSH levels in the plasma when compared with controls. Approximately 14% of the neurons in the ARC were found to be morphologically intact, significantly higher than in the comparably treated female animals. The seminiferous tubules were atrophic histologically in only 3 of the 8 animals; the remaining animals had tubules, similar to those of control animals. The histochemical activity of HSD in the interstitial cells was weaker than that seen in control animals. The results of this investigation suggest that the injection of MSG in females on both Day 7 and Day 8 of the neonatal period results in a lesion of the ARC that is more severe than that found in a similar group of male hamsters or in females given MSG on Day 7 or Day 8 alone. In addition all female animals were acyclic with this treatment. These results also substantiate previous reports in which MSG-induced lesions of the ARC result in alterations in FSH, but not LH, secretion in the hamster.