Fig. 3. The muscarinic acetylcholine receptor (mAChR) subtype involved in carbachol-induced extracellular signal-regulated kinase (ERK) activation in PC12 cells. ( A ) Carbachol-induced ERK activation insensitive to pertussis toxin. The cells were treated with or without 10 ng/ml pertussis toxin (PTX) for 21 h and then stimulated with the presence (+) or the absence (−) of 1 mM carbachol for 2 min. ( B ) The effects of mAChR antagonists on carbachol-induced ERK activation. The cells were stimulated with or without 1 mM carbachol in the presence (+) or the absence (−) of 10 μM pirenzepine (PZP) or 4-diphenyacetooxy-1,1-dimethylpiperidinium (4-DAMP). The antagonists were added 10 min before the addition of carbachol. 
-ERK1 and 
-ERK2 indicate activated ERK1 and ERK2.
