MAPK8 and cardiac hypertrophy: In the present study we reported several interesting findings: (1) M3-mAChR is upregulated during Ang II-induced cardiac hypertrophy both in vivo and in vitro; (2) Upregulation of M3-mAChR could inhibit cardiac hypertrophy induced by chronic Ang II infusion; (3) Upregulation of M3-mAChR is mediated by decreased phosphorylation of ERK, JNK, and p38 MAPK cascades through the downregulation of AT1 R. These results provide novel insight into the mechanisms underlying the cardioprotective effects of M3-mAChR in cardiac hypertrophy, and indicate that M3-mAChR is a potential therapeutic target.