Steroid hormone target sites in the brain: The differential distribution of estrogen, progestin, androgen and glucocorticosteroid

Abstract

Nuclear concentration of steroid hormones or their metabolites exists in neurons in selective areas of the mammalian brain. The distribution of estrogen target cells in different mammalian species appears to follow a similar pattern that involves selective nuclear groups in the forebrain, midbrain and lower brainstem. The distribution of androgen target cells in the rat brain largely corresponds to the distribution of estrogen target cells, with differences existing, however, in certain structures, such as lateral septum, ventromedial hypothalamus, hippocampus, cortex, epithalamus, lower brainstem and spinal cord. The distribution of progestin in the guinea-pig hypothalamus seems restricted to the preoptic and infundibular region, where it overlaps with estrogen localization. Corticosterone target cells are accumulated in extrahypothalamic regions, and not in the hypothalamus, in contrast to the sex steroid. The synthetic “glucocorticosteroid” dexamethasone, however, is found in neurons and glial cells throughout the rat brain, differing from the natural glucocorticosteroid corticosterone. Localization of different hormones in neurons of identical regions suggests that the same neuron may be addressed by different hormones. On the other hand, the differential distribution of the various types of hormones is likely to reflect differences in their action. Both estrogens and androgens appear to act on neural structures that are identical to or closely associated with (1) various sensory pathways and (2) ventricular recess organs, constituting the periventricular gland. Androgens, in addition, stimulate selectively neurons of the somatomotor system and circuits of aggression. In general, the wide existence of hormone target cells in the central nervous system reflects the multiple actions of the steroid hormones on endocrine regulation, autonomic functions and behavior.