Abstract
We have previously demonstrated that the peripheral vasopressin (AVP) system participates in the control of renal sympathetic nerve activity (RSNA), and suppresses Fos-like immunoreactivity (FLI), as a neuronal marker, in the paraventricular nucleus (PVN) of the hypothalamus, via the vasopressin V1 receptor during central salt loading in conscious rats. The present study examined the effects of endogenous vasopressin on AVP and oxytocin (OT) mRNA production in the PVN and supraoptic nucleus (SON) of the hypothalamus in response to central salt loading. Either vasopressin V1 receptor antagonist, OPC-21268, or vehicle were administered into lateral ventricle 30 min before the central salt loading (0.67M NaCl at 1 μl/min for 20 min). In situ hybridization assays with highly specific synthetic oligodeoxyribonucleotide probes were used to detect the distribution of AVP and OT mRNA. The PVN was divided into three areas, including the medial magnocellular part (PVM), the lateral magnocellular part (PVL), and the posterior portion (PVPO). In the groups pretreated with OPC-21268, the distribution of the hybridization signal on the x-ray films obtained from AVP and OT probe were decreased in the SON and PVL, and in the SON, respectively. These results suggest, at the cellular level, that central vasopressin stimulates its own synthesis in the PVN and SON, and also affects the synthesis of OT in the SON. [Jpn J Physiol 55 Suppl:S204 (2005)]
