Abstract
We have identified and visualized the vasopressin (VP) receptors expressed by hypothalamic magnocellular neurons in supraop-tic and paraventricular nuclei. To do this, we used RT-PCR on total RNA extracts from supraoptic nuclei or on single freshly dissociated supraoptic neurons, and in situ hybridization on frontal sections of hypothalamus of Wistar rats. The RT-PCR on supraoptic RNA extracts revealed that mainly V 1a , but also V 1b , subtypes of VP receptors are expressed from birth to adult-hood. No V 2 receptor messenger RNA (mRNA) was detected. Furthermore , the single-cell RT-nested PCR indicated that the V 1a receptor mRNA is present in vasopressinergic magnocellular neurons. In light of these results, in situ hybridization was performed to visualize the V 1a and V 1b receptor mRNAs in supraoptic and para-ventricular nuclei. Simultaneously, we coupled this approach to: 1) in situ hybridization detection of oxytocin or VP mRNAs; or 2) immu-nocytochemistry to detect the neuropeptides. This provided a way of identifying the neurons expressing perceptible amounts of V 1a or V 1b receptor mRNAs as vasopressinergic neurons. Here, we suggest that the autocontrol exerted specifically by VP on vasopressinergic neurons is mediated through, at least, V 1a and V 1b subtype receptors.