Role of α1-adrenoceptors of the locus coeruleus in self-stimulation of the medial forebrain bundle

Abstract

The present experiments were undertaken to clarify the role of central α1-adrenoceptors in reward processes. Rats, trained to self-stimulate via electrodes in the medial forebrain bundle of the lateral hypothalamus, were administered α1-selective drugs near the locus coeruleus (LC), a site of a dense concentration of α1- receptors. Effects on reward potency were assessed from shifts in rate-frequency curves while effects on motor response capacity were judged from changes in the maximal rates of responding. It was found that local blockade of LC α1-receptors with terazosin produced a significant dose-dependent and site-dependent rightward shift of 0.08 log units and a significant decrease of 16.3% in the maximum response rate. Both effects were completely reversed by coadministration of the α1-agonist, phenylephrine and were not attributable to terazosin's weak action at α2-adrenoceptors. It is concluded that LC α1- adrenoceptors are involved both in reward/motivational processes and operant response elaboration which are postulated to work together to facilitate goal attainment. © 2007 Nature Publishing Group All rights reserved.