Roles of β- and α2-adrenoceptors within the central nucleus of the amygdala in the visceral pain-induced aversion in rats.

We investigated the roles of β- and α(2)-adrenoceptors within the central nucleus of the amygdala (CeA) in the negative affective and sensory components of visceral pain in rats. We observed a dose-dependent reduction of intraperitoneal acetic acid-induced conditioned place aversion by bilateral injections of timolol, a β-adrenoceptor antagonist, or clonidine, an α(2)-adrenoceptor agonist, without reducing writhing behaviors. These data suggest a pivotal role of intra-CeA adrenoceptors in the negative affective, but not sensory, component of visceral pain.