α 1- and β-Adrenergic receptors are co-regulated during both noradrenergic denervation and hyperinnervation

Abstract

Changes in the density of α 1- and β-adrenergic receptors were studied following denervation of rat cerebral cortex and hyperinnervation of cerebellum and motor trigeminal nucleus, caused by neonatal 6-hydroxydopamine treatment. Four well-defined thalamic projection zones to cortex were studied separately using tissue punch methodology. Both α 1- and β-adrenergic receptors were unevenly distributed in motor, sensory, visual and auditory cortex. The density of α 1-adrenergic receptors correlated better with the norepinephrine content of the punches ( r = 0.62) than did the density of β-adrenergic receptors ( r = 0.38). Noradrenergic denervation increased both α 1>- and β-adrenergic receptor density in almost all cortical areas studied, however the percentage increase was larger for β than α 1-adrenergic receptors. The change in receptor density was largest in visual cortex and smallest in somatosensory cortex for both receptor sub-types. Noradrenergic hyperinnervation caused a 15–18% decrease in both α 1- and β-adrenergic receptor density in the motor trigeminal nucleus of the pons, but did not change the density of either receptor type in the cerebellum. In general, following either noradrenergic denervation or hyperinnervation the change in α 1-adrenergic receptor density was correlated ( r = 0.64, P < 0.005) with the change in β-adrenergic receptor density in each region, suggesting that these different receptor sub-types are under similar control mechanisms.