Th central noradrenergic system in the rat: metabolic mapping with alpha-adrenergic blocking agents

Rates of cerebral glucose utilization were measured by means of the autoradiographic 2-deoxy-D-[14C]glucose technique in 73 normal, awake rats treated with different doses of the alpha-adrenergic blockers, phenoxybenzamine, phentolamine and yohimbine. Three types of responses were elicited by the administration of these drugs. The predominant effect observed after administration of all alpha-blockers was a widespread depression of glucose utilization, particularly within the neocortex. The effect was most pronounced with phenoxybenzamine. In a few structures (locus coeruleus, interstitial nucleus of the stria terminalis, medial forebrain bundle, periventricular nucleus and some medullary and hypothalamic nuclei associated with the regulation of blood pressure) marked increases in glucose utilization were observed. Administration of phentolamine resulted in increased glucose utilization in all the central components of the auditory system (cochlear n., superior olivary n., n. lateral lemniscus, inferior colliculus, medial geniculate body and auditory cortex). Phenoxybenzamine and yohimbine tended to decrease glucose utilization in the auditory system. Alternating columns with higher and lower rates of local glucose consumption were observed in most of the neocortical areas and in the cerebellar vermis. The significance of these columns is not clear.