The modulation of dopamine-sensitive adenylate cyclase activity in the mouse caudate nucleus by estradiol

Progesterone effects upon dopamine release from the corpus striatum of female rats. II. Evidence for a membrane site of action and the role of albumin

In the present experiment we used immobilized progesterone linked to bovine serum albumin (P4-3-BSA) as a probe to examine whether the effects of a direct in vitro infusion of progesterone upon dopamine (DA) release from corpus striatal (CS) tissue fragments from ovariectomized estrogen-treated rats may be attributable to a surface membrane site of action. In Expt. I, a direct in vitro pulsatile infusion of P4-3-BSA resulted in two discrete episodes of stimulated DA release which were not observed in superfusions receiving a continuous infusion of P4-3-BSA or compared to data of control superfusions. In contrast to that of a pulsatile administration, a continuous infusion of P4-3-BSA completely abolished the amphetamine-stimulated response from these tissue preparations with significantly lower DA release rates compared to the pulsatile P4-3-BSA (P less than 0.02) and control (P less than 0.04) conditions. In Expt. II, the addition of tetrodotoxin (TTX, 1 microM) to the superfusion medium abolished the discriminatory response between pulsatile and continuous administration of immobilized progesterone. These results indicate that the action of progesterone on DA release from the CS is mediated primarily through a surface membrane site of an interneuron(s) which can discriminately respond to a specific infusion mode of this steroid.

Estrogen regulation of rat anterior pituitary adenylate cyclase

The effect of chronic estrogen treatment on the stimulation and dopamine inhibition of anterior pituitary (AP) adenylate cyclase (AC) activity was examined. Treatment of ovariectomized female rats with estradiol for 21 days resulted in a 450% increase in AP weight compared to ovariectomized controls. Stimulation of AC by guanine nucleotides (GN) (1 nM-0.1 mM) and vasoactive intestinal peptide (1 microM) was reduced by 50%. Stimulation of AC by fluoride ions was unchanged by estradiol treatment. Stimulation above basal by forskolin was reduced by variable amounts (23-50%), and depended on the concentration of forskolin used. Inhibition of AC mediated by D2-dopamine receptors was decreased by 45%. Estrogen treatment had no effect on the toxin-catalyzed incorporation of [32P]ADP into stimulatory and inhibitory GN regulatory proteins. These results indicate that the effect of estrogen on the anterior pituitary include modulation of stimulated, dopamine-inhibited and basal AC activity.