Elsevier Inc. Gnai proteins in ACh Rgs4 Rgs6 Gnaq proteins in ACh G protein mediated signaling pathway via Galphai family released ACh acetylcholine Ca2+ DAG G protein mediated signaling pathway via Galphaq family choline ---> acetylcholine ACh hydrolysis, signal termination ---> choline Ache Grk5 ---| ai-Chrm2 Grk5 Grk5 ---| ai-Chrm4 Slc5a7 presynaptic autoreceptor ACh inhibition ---| released ACh presynaptic autoreceptor ACh inhibition released ACh ---> presynaptic autoreceptor ACh inhibition Rgs4 ---| Gnai proteins in ACh Rgs6 ---| Gnai proteins in ACh Rgs2 Adrbk1 ---| Chrm2 Adrbk1 ---| Chrm4 Adrbk1 ---| Chrm5 Adrbk1 Adrbk1 ---| Chrm1 Chrm1 Adrbk1 ---| Chrm3 Chrm3 cAMP Chrm2 ---- Gnai proteins in ACh Chrm4 ---- Gnai proteins in ACh Chrm5 Chrm5 ---- Gnaq proteins in ACh Chrm3 ---- Gnaq proteins in ACh Chrm1 ---- Gnaq proteins in ACh Chrm2 ---- released ACh Chrm4 ---- released ACh calcium/calcium-mediated signaling pathway calcium transport pathway IP3 acetylcholine ---> released ACh Chrm1 ---- released ACh Chrm3 ---- released ACh Chrm5 ---- released ACh ai-Chrm2 ---- released ACh ai-Chrm4 ---- released ACh released ACh ---> ACh hydrolysis, signal termination Slc18a3 acetyl-CoA Chat choline protein kinase C (PKC) signaling pathway IP3 --+> Ca2+ G protein mediated signaling pathway via Galphai family ---| cAMP Chrm2 decreased heart rate Chrm2 ---> decreased heart rate Chrm3 ---> bronchoconstriction ACh hydrolysis, signal termination Chrm4 Chrm4 ---> synaptic plasticity synaptic plasticity Chrm1 ---> synaptic plasticity bronchoconstriction G protein mediated signaling pathway via Galphaq family --+> IP3 G protein mediated signaling pathway via Galphaq family --+> DAG Rgs2 ---| Gnaq proteins in ACh ai-Chrm2 ai-Chrm4 cholinergic neuron acetyl-CoA ---> acetylcholine