α ₂-Adrenoceptors: Challenges and Opportunities—Enlightenment from the Kidney

Figure 1

Distribution of α-adrenoceptors. Illustration summarizes our conclusion that normally α₁-ARs dominate the postjunctional membrane in the neuroeffector junction (a); however, following chronic treatment with an α₁-AR antagonist or in genetic hypertension, α₂-ARs become the dominant α-adrenoceptor subtype residing within the postjunctional membrane (b). In both cases, α₂-ARs are also localized to the prejunctional and extrajunctional membranes. This model was tested using subpressor levels of renal sympathetic nerve stimulation (RSNS) with sodium excretion as the outcome measure and, therefore, applies to sympathetic regulation of sodium reabsorption by renal epithelial cells; however, we hypothesize that similar changes in α₂-ARs may occur in the renal vasculature and may contribute to sodium retention and hypertension. The dotted line (-----) denotes a diffusion barrier that hampers the entry of norepinephrine (NE) into the neuroeffector junction.

(a)

(b)