Progesterone in rat brain: modulation of beta-adrenergic receptor activity

Cytosolic proteins binding specifically the progesterone analogue 3H R5020 can be detected in various areas of the central nervous system (CNS) of rat. Our study demonstrates that the concentration of progesterone receptors in the brain of adult, ovariectomized, female rats is maximal in frontal cortex and midbrain and lowest in the cerebellum. Short term administration of the hormone does not alter the beta-adrenergic receptor system, while a prolonged administration of progesterone results in an up-regulation of 3H-DHA binding in the frontal cortex. Such increase in binding activity is due to an increased number of beta-adrenergic receptors. Furthermore, high doses of progesterone can also increase the number of beta-adrenergic binding sites in an "in vitro" system where brain slices are incubated for few hours in a physiological medium.