Abstract
The distributions of two newly discovered receptors, the vasopressin-activated calcium-mobilizing receptor (VACM-1) and the dual angiotensin II/vasopressin receptor (A II /AVP), in the central nervous system (CNS) of the rat were determined using reverse transcriptase-polymerase chain reaction and in situ hybridization. The sequence of the rat VACM-1 cDNA was determined and found very homologous to the rabbit and human sequences. Both VACM-1 and A II /AVP receptor genes were widely expressed in the brain, but differed according to the cell type studied. Glial cells were very faintly labelled. The epithelial cells of the choroid plexuses, the ependymal cells and the pia mater were all labelled. Both genes were most active in neurones throughout the CNS. VACM-1 and A II /AVP receptors were detected in neurones previously shown to possess V 1a and V 1b vasopressin receptors, and/or the AT1 and AT2 angiotensin II receptors in many brain areas. This was the case for the magnocellular neurones of the supraoptic and paraventricular nuclei of the hypothalamus. We suggest that the VACM-1 and A II /AVP receptors may account for the V 2-like responses to vasopressin by these neurones which lack a genuine V 2 vasopressin receptor.