Figure 4. The depolarization of layer II parasubicular neurons induced by carbachol (CCh) is likely mediated by M₁ receptors.

A. Voltage traces from a representative PaS neuron show that application of CCh alone (50 µM; black bar) depolarizes membrane potential (A₁), and that 15-min bath application of the selective M₁ receptor antagonist, pirenzepine (PIR; 1 µM; white bar) blocked the depolarization induced by CCh. Note that hyperpolarizing and depolarizing current pulses were used to assess alterations in input resistances and cell firing from a potential of −60 mV. B. Group data show that the depolarization of membrane potential induced by application of 50 µM CCh was blocked by pirenzepine (PIR; 1 µM), but not by the M₂ receptor blocker, methoctramine (Methoc; 1 µM), suggesting that M₁, but not M₂ receptors, mediate the cholinergic depolarization of layer II PaS neurons (**: p<0.01).