α- And β-adrenoreceptor blockers have opposite effects on energy metabolism of the central auditory system

Abstract

THE autoradiographic ¹⁴C-deoxyglucose assay has made it possible to measure the local rates of glucose utilisation (LCGU) simultaneously in all the macroscopic components of the central nervous system¹. Because of the close relationship between local cerebral functional and metabolic activities, the method has proved useful in mapping the distribution of alterations in cerebral functional activity in experimental physiological states², and to identify components of cerebral dopaminergic systems in studies with the dopamine agonists, apomorphine³ and amphetamine⁴. Noradrenergic systems, including both α- and β-adrenergic receptors, have been identified in brain and implicated in various behavioural and affective states in man and animals^5,6. Drugs with α- or β-adrenergic blocking actions exhibit effects on mood and behaviour^5,6. Propranolol, a β-adrenergic blocking agent, has, in fact, been used as a therapeutic agent in the control of psychotic symptoms^7,8. In an attempt to localise the regions of the brain in which functional and/or metabolic activities are altered by adrenergic blockade, we have used the ¹⁴C-deoxyglucose method to study the effects of the β-adrenergic blocker, DL-propranolol, and the α-adrenergic blocker, phentolamine. The results demonstrate strikingly opposite effects of these drugs in the auditory system of the rat.