Central pressor actions of neurokinin B: increases in neurokinin B contents in discrete nuclei in spontaneously hypertensive rats

The regional distributions of neurokinin B-like immunoreactivity and substance P-like immunoreactivity in the central nervous system in spontaneously hypertensive rats (SHRs) and normotensive Wistar Kyoto rats (WKYs) were examined. The distribution of neurokinin B-like immunoreactivity in WKYs was not exactly the same as that of substance P-like immunoreactivity. The neurokinin B-like immunoreactivity contents of the supraoptic nucleus of the hypothalamus and the caudal part of the nucleus tractus solitarii were higher in SHRs than in WKYs. Injections of selective neurokinin B receptor peptides, senktide (suc-[Asp⁶,Me-Phe⁸]-substance P_6–11) and [Pro⁷]-neurokonin B, into the lateral brain ventricle of the normotensive rats caused dose-dependent increases in the blood pressure, and blockade of peripheral vascular vasopressin receptors reduced these pressor responses, but did not affect the substance P-induced pressor response. These findings suggest that the novel tachykinin peptide, neurokinin B has an important role in central pressor action in rats.