Table 1.

Summary of muscarinic receptor functions affected in genetically altered mice

Genetic model	Functional responses to muscarinic agonist	Other phenotypic manifestations
M1 muscarinic receptor	Disrupted pilocarpine-induced seizures
knockout mice (6)	Absence of M-current potassium channel modulation in sympathetic ganglion neurons
	Preserved pilocarpine-induced salivation
	Preserved pilocarpine-induced tremor
M2 muscarinic receptor	Disrupted oxotremorine-induced tremor
knockout mice (4)	Diminished oxotremorine-induced analgesia
	Attenuated oxotremorine-induced hypothermia
	Altered muscarinic regulation of heart rate
	Preserved oxotremorine-induced salivation
M4 muscarinic receptor knockout mice (5)	Preserved hypothermia, salivation, tremor, analgesia induced by oxotremorine	Hyperactivity and D1 dopamine receptor supersensitivity