The neurokinin-1 receptor antagonist WIN51,708 attenuates the anxiolytic-like effects of ventralpallidal substance P injection.

We reported previously that the neurokinin substance P has anxiolytic-like effects when administered into the nucleus basalis of the rat ventral pallidum. The present study aimed to determine the possible involvement of the neurokinin-1 receptor in the anxiolytic action of intrabasalis substance P injection. Behavioral testing was performed in the rat elevated plus-maze model of anxiety. Microinjection of substance P (1 ng) into the nucleus basalis increased sojourn times on the open arms, excursions into the end of the open arms and scanning over the edge of an open arm, indicative of an anxiolytic-like profile. The non-peptide neurokinin-1 receptor antagonist WIN51,708, administered i.p. 20 min prior to intrabasalis substance P injection, antagonized the anxiolytic effects of the neurokinin in a dose-dependent manner. WIN51,708 at 10 mg/kg diminished, while at the higher dose of 20 mg/kg the antagonist completely blocked, the effect of substance P on anxiety-related behaviors. These findings suggest that the anxiolytic-like effects of substance P in the nucleus basalis are mediated through neurokinin-1 receptive sites.