Alpha 1-adrenoceptor denervation supersensitivity in brain: physiological and receptor binding studies.

Electrophysiological and radioligand binding methods were used to characterize noradrenergic denervation supersensitivity at alpha 1-adrenoceptors in rat thalamus. Denervation was accomplished either by intraventricular or intracerebral injection of the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA). In the physiological studies, the sensitivity of single lateral geniculate neurons to norepinephrine, carbachol, and serotonin was compared in sham and lesioned animals various times after 6-OHDA. Conducted in parallel were radioligand binding studies in which the density and affinity of thalamic alpha 1-adrenoceptors were measured with the specific antagonist [3H]prazosin. The results indicate that denervation produces a selective increase in the sensitivity of geniculate neurons to alpha 1-adrenergic stimulation and a concomitant increase in alpha 1-adrenoceptor density and agonist affinity.