Figure 3.

Dependence of the carbachol effect on activation of M1-receptors and PKC. (A) Fold increase in sEPSC frequency above control values (Cont = 1) under the following conditions (solutions contained 100 μM Cd²⁺ and 0.2 μM tetrodotoxin): Carb, 200 μM carbachol; Hexa, 10 or 100 μM hexamethonium + carbachol (200 μM); Atrop, 10 μM atropine + carbachol (200 μM); Nic., 40 μM nicotine. (B) The effect of carbachol (200 μM) on the sEPSC frequency was inhibited in a dose-dependent manner by the M1-antagonist pirenzepine (▪) but not by gallamine, a preferential M2-antagonist (□). (C) The carbachol effect depended on activation of G proteins and PKC, but not on elevation of [Ca²⁺]_i: untreated cells (Cont); cells treated with carbachol alone (Carb, 200 μM), or after pretreatment with one of the following substances: PTX (150 ng/ml for 14–19 h); BAPTA (2–10 μM BAPTA-AM for >30 min); staurosporine (Staur, 800 nM for 70–100 min); β-PMA or α-PMA (100 nM 4β- or 4α-PMA for 14–19 h). ∗, P < 0.05 and ∗∗, P < 0.01 (vs. Cont); ++, P < 0.01 (vs. Carb). The number of cells tested is indicated above each bar.