AROMATASE-IMMUNOREACTIVE CELLS ARE PRESENT IN MOUSE-BRAIN AREAS THAT ARE KNOWN TO EXPRESS HIGH-LEVELS OF AROMATASE-ACTIVITY

The transformation of testosterone into estradiol in the brain plays a key role in several behavioral and physiological processes, but it ha s been so far impossible to localize precisely the cells of the mammal ian brain containing the relevant enzyme, viz., aromatase. We have rec ently established an immunohistochemical technique that allows the vis ualization of aromatase-immunoreactive cells in the quail brain. In th is species, a marked increase in the optical density of aromatase-immu noreactive cells is observed in subjects that have been treated with t he aromatase inhibitor, R76713 or racemic Vorozole. This increased imm unoreactivity, associated with a total blockade of aromatase activity, has been used as a tool in the present study in which the distributio n of aromatase-immunoreactive material has been reassessed in the brai n of mice pretreated with R76713. As expected, the aromatase inhibitor increases the density of the immunoreactive signal in mice. Strongly immunoreactive cells are found in the lateral septal region, the bed n ucleus of the stria terminalis, the central amygdala, and the dorso-la teral hypothalamus. A less dense signal is also present in the medial preoptic area, the nucleus accumbens, several hypothalamic nuclei (e.g ., paraventricular and ventromedial nuclei), all divisions of the amyg dala, and several regions of the cortex, especially the cortex pirifor mis. These data demonstrate that, contrary to previous claims, aromata se-immunoreactive cells are present in all brain regions that have bee n shown previously to contain high aromatase activity.