Feeding behaviour alteration in rats due to neonatal monosodium glutamate (MSG) administration

A. P. GARCÍA; SALAZAR V; C. ARIZNAVARRETA; M HERMANUSSEN; J. A. F. TRESGUERRES

Praga

Workshop; EURISKED/CREDO. Cluster Workshop on Multi-organic Risk Assestment of Endocrine Disrupters; 2005

ABSTRACT Obesity, advanced vaginal opening, altered pattern of gonadal hormonal secretion, irregular cycling, altered sexual behaviour and infertility are the effects described for the neonatal parenteral administration of monosodium glutamate (MSG) to rats. The actual experiment was conducted to determine the potential effects of oral MSG administration on some parameters of pubertal development and the reproductive system. To achieve this objective thirty Wistar pregnant rats were divided in four groups (control, injection, MSG 2,5 and MSG 5 group), receiving diets containing 0, 0, 2.5, or 5.0 g/day MSG respectively from day 14th of pregnancy onwards. Offspring injection group was neonatally s.c. injected with MSG (4mg/g BW) on alternate days for the first 10 postnatal days (day 2, 4, 6, 8, 10). The other groups received saline solution injections on the same days. After weaning, MSG feeding was continued in the offspring at the same concentrations until day 90 of life. From day 22 onwards, vaginal opening, occurrence of 1st estrous and preputial separation was checked daily. Half of the pups were sacrificed at day 30 of life and the rest at day 90 by decapitation. Testis, seminal vesicles, uterus and ovaries were collected. Plasma was also obtained for the determination of Luteinizing Hormone (LH) and Testosterone. An important delay of vaginal opening and 1st estrous occurrence in both groups receiving MSG orally was observed (p 0,05). In contrast, parenteral neonatal MSG administration induced an evident advancement (p 0,01). The animals presented neither significant changes in the relative weight of ovaries and uterus nor in LH plasma levels. Males injected with MSG showed an important decrease in testis relative weight at 30 days of life (p0,01), similarly, significant reductions were observed in plasma LH levels (p0,01) and testosterone testis levels (p 0,05) at 90 day of life. However, in this group no effect on vesicles seminal relative weight and the time occurrence of preputial separation was detected. The animals treated orally did not present changes in testis and seminal vesicles relative weight nor in preputial separation occurrence time, although it was observed a slight decreased in LH plasma levels and a very significantly decreased in Testosterone testis concentration (p0,01). We can conclude that offspring pre-pubertal development and reproductive parameters are affected by oral intake of MSG in a different manner than the rats administered parenterally with this substance, being the effects more evident in the reproductive development of female pups.