Immobility from administration of the α1-adrenergic antagonist, terazosin, in the IVth ventricle in rats

Abstract

Brain α1-adrenoceptors have been shown to be essential for motor activity and movement in mice using intraventricular injection of α1-antagonists. To facilitate subsequent neuroanatomical mapping of these receptors, the present study was undertaken to replicate these effects in the rat. Rats were administered the α1-antagonist, terazosin, in the absence and presence of the α1-agonist, phenylephrine, in the IVth ventricle and were tested for their motor activity responses to an environmental change. Terazosin was found to produce a dose-dependent, virtually complete cessation of behavioral activity that was reversed by coinfusion of phenylephrine. The results could not be explained by sedation. It is concluded that central α1-adrenoceptors are essential for behavioral activation in rats as in mice. © 2003 Elsevier Ireland Ltd. All rights reserved.