LOCALIZATION OF ARGININE-VASOPRESSIN V-1A RECEPTORS ON SYMPATHOADRENAL PREGANGLIONIC NEURONS

Vasopressin-containing nerve terminals are present in the spinal cord of several species. This study was designed to determine whether sympa tho-adrenal preganglionic neurones (SPN) express vasopressin receptors (VPRs). SPN in the spinal cord were revealed by retrograde labelling of Fluorogold following its unilateral injection into the adrenal medu lla of 12-20 day postnatal rats. VPRs were simultaneously visualised i n the Fluorogold-labelled slices of spinal cord using a recently devel oped biotinylated vasopressin receptor antagonist yl-D-tyrosine,6-argi nine,8-arginine,9-lysinamide(N epsilon-biotinamidocaproamide)] vasopre ssin, PhAcAL(Btn)VP. The VPR:PhAcAL(Btn)VP complexes were visualised e ither with Texas Red-conjugated avidin or with a Vectastain avidin:alk aline phosphatase detection kit. These dual-labelling experiments reve aled VPRs to be present in the spinal grey matter and to be particular ly dense in the intermediate grey matter and adjacent regions of the v entral horn. Many SPN were associated with receptor-specific labelling of PhAcAL(Btn)VP, thereby demonstrating that VPRs are expressed by th ese neurones. These VPRs were pharmacologically defined as the VI, sub type. It is concluded that sympatho-adrenal preganglionic neurones exp ress VPRs and that these are of the Vt, subtype. The distribution of V PRs is not, however, restricted to these SPN in the spinal cord.