THE NEONATAL NEUROTOXICITY OF MONOSODIUM L-GLUTAMATE ON THE SEXUALLY DIMORPHIC NUCLEUS OF THE PREOPTIC AREA IN RATS

The neurotoxic effect of monosodium L-glutamate (MSG) on the morpholog ies in the darkly stained sexually dimorphic nucleus of the preoptic a rea (SDN-POA) and the lighter-staining surrounding area (non-SDN-POA) within the medial preoptic nucleus (MPN) was evaluated. Male and femal e Long-Evans rats were used. MSG (4 mg/g of body weight) was administe red subcutaneously to pups on days 1 and 3 postnatally. Normal saline was used as the vehicle. At the age of 6 months, the rats were sacrifi ced and the brain tissues were fixed for histological examination. The morphological changes, i.e., total volume, density, total neuron numb er, neuronal nuclear volume (NNV) and ratio of pyknosis, of the SDN-PO A and non-SDN-POA within the MPN, were estimated using the AMS VIDS II I semiautomatic image-analytic system. The results indicated that neon atal MSG treatment caused significant neuronal loss and decreases in t otal volume of the SDN-POA and non-SDN-POA of male and female rats. Ho wever, only the SDN-POA of MSG-treated male rats showed a significant increase of pyknosis and a decrease of neuronal density, ,4 significan t enlargement of NNV in the SDN-POA and non-SDN-POA was observed in MS G-treated male rats. These results indicate that the MPN shows sex-spe cific and area-specific changes after neonatal neurotoxicity due to MS G.