17β-estradiol regulates nNOs and eNOS activity in the hippocampus

Estrogen treatment in symptomatic postmenopausal women appears to improve cognitive performance including memory, an effect which may involve enhanced nitric oxide formation in hippocampal neurons. To study whether 17beta-estradiol (E2) affects NO synthase activity in the hippocampus, we investigated the influence of E2 on hippocampal NO synthase expression and activity in female rats. Ovariectomy, which significantly decreased E2 serum levels, reduced neuronal (nNOS) and endothelial NO synthase (eNOS) expression and Ca2+-dependent NOS activity. E2 substitution reversed these effects. It is concluded that E2 increases nNOS and eNOS expression and activity in female hippocampus and thus improves hippocampal function.