FIGURE 3.
Simultaneous activation of α2A and βARs by application of Epi results in accelerated endocytosis of endogenously expressed α2AARs in native neurons. A, neurons (SpWT, subjected to α2AAR prelabeling as in Fig. 1, B and C) were stimulated by application of Epi (plus prazosin) in the absence or presence of the βAR antagonist propranolol, conditions that allow for activation of both α2A and β ARs or α2AARs alone, respectively. Significant endocytosis, as indicated by the appearance of intracellular punctae containing internalized receptors (arrows), was observed in response to Epi alone at both 5 and 10 min, whereas Epi together with propranolol drove observable endocytosis only at 10 min. B, quantitation of agonist-mediated α2AAR endocytosis in Epi-stimulated neurons the absence or presence of propranolol, with relative internalization determined as described under “Experimental Procedures.” Internalization by Epi alone was significantly attenuated by propranolol at both 5 and 10 min. Confocal images are representative of at least three independent samples, and quantitation was performed over at least 12–14 neurons. *, p < 0.01 versus Epi alone.