Figure 3.

Pharmacology of afterpotential modulation in granule cells. A, Left, Plot of the afterpotential response integral in CCh (2 μm) and after bath application of the M₁ mAChR antagonist pirenzepine (10 μm) and CCh. Pirenzepine abolishes the ADP response evoked by 50 pA depolarizing steps in CCh and restores the AHP normally present in granule cells under control conditions. Example traces shown above plot. Right, Bath application of the M₂ mAChR antagonist AF-DX 116 (1 μm; 50 pA step) does not block the ADP in granule cells. B, Bath application of the M₁ mAChR agonist MCN-A-343 (100 μm; 50 pA step) mimicked the effect of CCh and converted the normal AHP response into an ADP. Control and MCN-A-343 traces are shown overlapped on right. Action potentials truncated in the step responses in A and B are shown. All example responses in A are from approximately −55 mV; responses in B are from −50 mV. C, Summary of the effects of atropine and M₁ and M₂ receptor agents on the afterpotential integral in granule cells. *p < 0.01; **p < 0.0001.