Sexually dimorphic development of cholinergic enzymes in the rat septohippocampal system.

Cholinergic enzyme activity is sexually dimorphic in the rat hippocampal formation. Acetylcholinesterase (AChE) activity is greater in females than males in Ammon's horn/subiculum on the day of birth, but is equivalent in males and females at all older ages, suggesting an earlier maturation. Choline acetyltransferase (ChAT) activity also reaches adult levels earlier in female septum, and at day 18 and in adults is greater in the female dentate gyrus compared to males. Hippocampal weight relative to body weight is consistently greater in females at all ages, particularly in Ammon's horn/subiculum. Such regional sex differences during development and in adulthood suggests that cholinergic enzyme activity is regulated locally in the hippocampal target tissue.