Effects of progesterone on newly synthesized proteins in the ventromedial hypothalamus of the estrogen-primed female rat

The purpose of this work is to understand the basic neurochemical processes by which progesterone affects behavior. Sexual behavior in the female rat is an appropriate model because it is completely dependent on exposure of the medial basal hypothalamus to estrogen and progesterone. These hormones are thought to exert their effects by acting on DNA to alter protein synthesis. Alternatively, due to its short latency to act, progesterone may work by affecting cyclic nucleotide activity.Sex behavior can be blocked by the administration of protein synthesis inhibitors concurrent with estradiol and/or progesterone. These agents interfere with cyclic AMP accumulation as well as protein synthesis. Taken together, these results suggest several possibilities by which progesterone might modify protein action to induce behavioral effects. Alteration in tissue protein patterns (de novo synthesis and/or structural modification of new or pre-existing proteins) may be an essential part of hormone action.We have examined whether progesterone facilitation of sexual behavior is correlated with modification of two-dimensional gel protein patterns in the ventromedial hypothalamus (VMH) and midbrain central gray (MCG). Ovariectomized rats were divided into three groups: a vehicle-injected control group, an estrogen group and an estrogen plus progesterone group. Radiolabeled cysteine and methionine were infused in the VMH after progesterone injection. Following infusion, animals were tested for sexual behavior and sacrificed. The VMH and MCG were assayed for abundance changes in newly synthesized proteins using two-dimensional gel electrophoresis followed by fluorography.Analysis of approximately 660 spots/gel indicated that no proteins were consistently induced or lost as a result of being treated by progesterone. Therefore, we concluded that progesterone does not cause detectable alterations in VMH or MCG protein patterns between 10-100 kDa in the 4.8-6.7 apparent pI range. Such findings increase the likelihood that progesterone is acting through a non-genomic mechanism. In support of the validity of these findings, we have detected several proteins which change in response to estrogen administration when compared with no hormone controls. These findings appear to replicate and extend the work of Condon, Lynn, and Roy (1989).U of I OnlyETDs are only available to UIUC Users without author permissio