Analogies between oxytocin systems of the uterus and brain.

In this brief review we have compared OT systems in the brain with those of the uterus and ovary particularly with respect to interactions with steroids. We have presented evidence of heterogeneous OTR and 125I-P-3-BSA binding sites in the MPOA as well as evidence of extensive interactions of steroids and OT in the MPOA, that cannot be adequately explained by genomic effects of steroids. We also discuss a putative analogue between steroid control of OTR stimulation of intracellular calcium levels, phospholipase C activity and prostaglandins in the uterus and steroid effects on OT systems in brain. We have developed a model for steroid control of both OT release and OTR in which we suggest that steroids and OT bind to membrane receptors coupled to G proteins. This model may prove useful in understanding the interactive central actions of steroids and OT systems in regulating the endocrinology and behaviors associated with reproduction.