Figure 4. Effects of adrenoceptor antagonists on the NA-induced current (I_NA).

All recordings were performed in an external solution containing 20 mm K⁺ at a V_H of −80 mV. The neurones were pretreated for 15 s with each adrenoceptor antagonist before the simultaneous application of 10⁻⁶ m NA. A, yohimbine inhibited I_NA in a concentration-dependent manner. B, the concentration-inhibition relationships for various NA antagonists on I_NA. All responses were normalized to the peak current induced by 10⁻⁶ m NA alone. Each point and the vertical bars represent the mean ±s.e.m. from 5 neurones.