Arginine-vasopressin neurons in the rat hypothalamus produce neurokinin B and co-express the tachykinin NK-3 receptor and angiotensin II type 1 receptor

Secretion of arginine-vasopressin (AVP) from the hypothalamic paraventricul ar (PVN) and supraoptic (SON) nuclei is induced by neurokinin B (NKB) and a ngiotensin. To characterize the mechanisms by which this occurs, we used im munohistochemical techniques to assess the ability of AVP-producing neurons to express NKB, NKB receptor (NK-3 receptor) and angiotensin II type 1 rec eptor (AT-1 receptor). Double fluorescence immunohistochemistry indicated t hat AVP-immunoreactive cell bodies in the PVN and SON, as well as their axo n varicosities in the posterior pituitary, co-express NKB. Almost all AVP-n euron perikarya also expressed both the NK-3 receptor and AT-1 receptor. Th us, AVP-producing neurons in the PVN and SON, which are regulated by NKB, a re themselves a source of NKB. Furthermore, the regulation of AVP release b y these neurons by NI(B and angiotensin II is mediated by the NK-3 receptor and the AT-1 receptor, respectively.