How are muscarinic cholinergic receptors?

Bind Ach and recognize muscarine an alkaloid in poisonous mushrooms, weak affinity, five subclasses (M1, M2, M3, M4, M5) only 123 are functionally characterized. Located on autonomic effector organs [heart, Smooth muscles, brain, exocrine], drugs usually act more on Ni receptors than these. Mechanism of action is G-protein coupled receptor slow response excitatory or inhibitory, M1 and M3 induces Gq activates Phospholipase C, M2 induces Gi inhibit adenylyl cyclase