THE V-1A AND V-1B, BUT NOT V-2, VASOPRESSIN RECEPTOR GENES ARE EXPRESSED IN THE SUPRAOPTIC NUCLEUS OF THE RAT HYPOTHALAMUS, AND THE TRANSCRIPTS ARE ESSENTIALLY COLOCALIZED IN THE VASOPRESSINERGIC MAGNOCELLULARNEURONS

We have identified and visualized the vasopressin (VP) receptors expre ssed by hypothalamic magnocellular neurons in supraoptic and paraventr icular nuclei. To do this, we used RT-PCR on total RNA extracts from s upraoptic nuclei or on single freshly dissociated supraoptic neurons, and in situ hybridization on frontal sections of hypothalamus of Wista r rats. The RT-PCR on supraoptic RNA extracts revealed that mainly V-1 a, but also V-1b, subtypes of VP receptors are expressed from birth to adulthood. No V-2 receptor messenger RNA (mRNA) was detected. Further more, the single-cell RT-nested PCR indicated that the V-1a receptor m RNA 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 paraventricular nuclei. S imultaneously, we coupled this approach to: 1) in situ hybridization d etection of oxytocin or VP mRNAs; or 2) immunocytochemistry to detect the neuropeptides. This provided a way of identifying the neurons expr essing perceptible amounts of V-1a or V-1b receptor mRNAs as vasopress inergic neurons. Here, we suggest that the autocontrol exerted specifi cally by VP on vasopressinergic neurons is mediated through, at least, V-1a and V-1b subtype receptors.