Figure 4.

β₁ adrenoceptors promote sympathetic neurite outgrowth. A, Superior cervical sympathetic ganglion neurons cultured without treatment extend many neurites. B, C, Addition of propranolol at a concentration of 10⁻¹⁰ m appeared to increase neurite outgrowth (B), and this was confirmed by quantitative analysis of peripherin-immunoreactive neurite area (C) (n = 12 per condition). D, E, Cultures treated in the presence of 10⁻⁸ m metoprolol (D) showed increased neurite outgrowth similar to propranolol, and this was confirmed by quantitative analysis (E) (n = 12). F, Treatment with the β₂-antagonist ICI 118551 had no effect on neurite outgrowth (n = 3). G, H, Counts of neuronal somas per unit area showed no differences between control cultures and those treated with propranolol (G) or metoprolol (H). Scale bar: (in D) A, B, D, 50 μm for all micrographs. Results are presented as the mean ± SEM. *p < 0.05 compared with control.