Effect of low estrogen on neurons in the preoptic area of hypothalamus of ovariectomized rats.
The purpose of this study was to investigate the difference in neuronal activity in the preoptic area of the hypothalamus (POAH) under low estrogen condition induced by ovariectomy. One hundred and twenty sham operated (SHAM) and ovariectomized (OVX) rats were placed in different temperatures for 2h. Twelve rats from each group were stimulated by 4degC, 10degC, 25degC, 33degC and 38degC, respectively. c Fos expression in the POAH was detected by immunohistochemistry. Following exposure to warm and cold stimuli, there were markedly lower c Fos positive cell densities in the OVX group compared with the SHAM group in the median preoptic nucleus (MnPO) at 4degC, 10degC, 33degC and 38degC, in the medial preoptic area (MPA) at 25degC and 38degC, in the ventromedial preoptic nucleus (VMPO) at 4degC, 10degC and 38degC and in the ventrolateral preoptic nucleus (VLPO) at 4degC and 38degC. Both temperature and surgery had an impact on c Fos expression by two way ANOVA method except in the lateral preoptic area (LPO) c Fos expression differed within different nuclei of the two groups in the same and different temperature stimuli. This indicated that the temperature sensitive nuclei in the POAH exhibited lower and different activities during temperature stimuli following ovariectomy, which possibly resulted in abnormal thermoregulation and menopausal symptoms.
Acta histochemica