Pretreatment of striatal neurons from mouse embryos in primary culture with 17 beta-estradiol (10(-9) M, 24 h) enhanced the ADP-ribosylation of G alpha o,i proteins catalyzed by pertussis toxin (PTX). As estimated by quantitative ADP-ribosylation of G alpha s with cholera toxin and immunoblot experiments using anti-G alpha o and anti-G beta sera, 17 beta-estradiol pretreatment did not modify the levels of the major GTP-binding protein (G protein) constituent subunits G alpha s, G alpha o, and G beta. Thus, 17 beta-estradiol should induce a qualitative modification of these G proteins, perhaps by stabilizing the association of the heterotrimers G alpha o,i beta gamma, which are the targets of PTX. Such a hypothesis is in agreement with observations indicating that 17 beta-estradiol both suppressed the D2 dopamine- and opiate receptor-induced inhibitions of adenylate cyclase activity and enhanced the positive coupling between biogenic amine receptors (D1 dopamine, beta-adrenergic, and A2 adenosine) and adenylate cyclase. In addition, PTX pretreatment, which is known to uncouple receptors associated with Go,i proteins and thus to impair the dissociation of the heterotrimers G alpha o,i beta gamma, mimicks the effects of the steroid on the responses of adenylate cyclase to inhibitory and stimulatory agonists. Finally, the chemical specificity of the steroids was the same in the ADP-ribosylation as in the adenylate cyclase experiments: Testosterone (10(-9) M) mimicked the effects of 17 beta-estradiol, whereas 17 alpha-estradiol, progesterone, and dexamethasone did not.(ABSTRACT TRUNCATED AT 250 WORDS)