Regional changes of brain Na+,K+-transporting adenosine triphosphatase related to ovarian function

Synaptosomal Na+,K+-transporting ATPase activity of the mediobasal hypothalamus (MBH), the medial preoptic-suprachiasmatic (POSC) region and cerebral cortex was measured in rats at different stages of the estrous cycle and after ovariectomy and estradiol replacement. Enzyme activity of the MBH and POSC showed cyclic changes. In both regions it increased shortly before the proestrus surge of LH. However, the two areas responded to castration and estrogen treatment in an opposite fashion. No changes were detected in enzyme activity in the cerebral cortex. These findings are consistent with previous reports on cyclic changes in electrical activity and suggest that Na+,K+-ATPase activity could be a useful indicator of neural activity for the study of neuroendocrine interactions.