Abstract
The activities of two enzymes involved in the oxidative part of the pentose cycle and one glycolytic enzyme have been measured by quantitative histochemical methods both in histologically pure nucleus supraopticus and in an adjacent area of the anterior hypothalamus of rat. In the nucleus supraopticus, glucose 6-phosphate dehydrogenase activity increased 34% and 6-phosphogluconate dehydrogenase activity declined by 9%, while lactic dehydrogenase activity did not change significantly after a thirsting period of 6 days. The nonsupraoptic, adjacent anterior hypothalamic area did not show significant changes in activity of any of the enzymes studied.