Heart The M2 muscarinic receptors are located in the heart, where they act to slow the
heart rate down to normal
sinus rhythm after negative stimulatory actions of the
parasympathetic nervous system, by slowing the speed of
depolarization. They also reduce contractile forces of the
atrial cardiac muscle, and reduce conduction velocity of the
atrioventricular node (AV node). However, they have little effect on the contractile forces of the
ventricular muscle, slightly decreasing force.
Airway smooth muscle Both M2 and M3 muscarinic receptors are expressed in the smooth muscles of the airway, with the majority of the receptors being the M2 type. Activation of the M2 receptors, which are coupled to Gi, inhibits the β-adrenergic mediated relaxation of the airway smooth muscle. Synergistically, activation of the M3 receptors, which couple to Gq, stimulates contraction of the airway smooth muscle.
IQ A Dutch family study found that there is "a highly significant association" between the
CHRM2 gene and intelligence as measured by the Wechsler Adult Intelligence Scale-Revised. A similar association was found independently in the
Minnesota Twin and Family Study. However, a larger 2009 study attempting to replicate this claim instead found no significant association between the
CHRM2 gene and intelligence.
Olfactory behavior Mediating
olfactory guided behaviors (e.g. odor discrimination,
aggression,
mating). == Mechanism of action ==