Monoamine oxidase activity in various parts of the rat brain during the estrous cycle.

The activity of monoamine oxidase was estimated in the hypothalamus, amygdala, and frontal cortex of adult female rats during the estrous cycle. Enzymatic activity in all three areas of brain was at its lowest during the diestrus phase of the estrous cycle and progressively increased to its highest during estrus. Throughout the estrous cycle the greatest activity of monoamine oxidase was found in the hypothalamus, as compared with the other brain areas. The significance of the activity is discussed.