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 beta- and alpha(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 beta-adrenoceptor antagonist, or clonidine, an alpha(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.