Evidence for the presence of nicotinic receptors on rat subfornical organ neurons

The sensitivity of subfornical organ (SFO) neurons in rat slice preparations to nicotine was studied using whole-cell patch-clamp recordings and immunohistochemistry. In the current-clamp mode, nicotine at 10 μM depolarized the membrane and increased the firing rate. In the voltage-clamp mode, nicotine elicited inward currents in a dose-dependent manner. The net current–voltage relationships of the nicotine-induced currents displayed inward rectification above −40 mV. The relatively α4β2-selective nicotinic acetylcholine (ACh) receptor antagonist, dihydro-β-erythroidine, reduced the peak amplitudes of the nicotine-induced inward currents. Immunohistochemical experiments with α4 antibody showed the existence of immunopositive cells in the subfornical organ. These results suggest that neurons in the subfornical organ are excited via α4β2 nicotinic acetylcholine receptors.