Regional Distribution of Choline Acetyltransferase Activity and Multiple Affinity forms of the Muscarinic Receptor in Heart
The autonomic nervous system plays an important role in the regulation of the heart. The parasympathetic division decreases heart rate and contractility while the sympathetic division mediates the opposite responses. The parasympathetic effect predominates at rest and provides tonic inhibitory influences. The parasympathetic system also predominates when both divisions are maximally stimulated (1). The preganglionic component of the parasympathetic system originates in the dorsal motor nucleus of the brain stem and courses to the heart through the vagus nerves. Postganglionic (intrinsic) neurons originate and terminate within the heart. Acetylcholine is the neurotransmitter of both the preganglionic and postganglionic divisions of the parasympathetic system. The response between the pre- and postganglionic neurons is mediated by the cholinergic nicotinic receptor. The postganglionic neurons interact with the myocardium and its specialized pacemaker tissue by means of the cholinergic muscarinic receptor. Choline acetyltransferase activity in heart is a neurochemical marker of both the pre- and postganglionic neurons of the parasympathetic system in unknown proportion.
KeywordsTyrosine Hydroxylase Muscarinic Receptor Choline Acetyltransferase Cholinergic Muscarinic Receptor Parasympathetic System
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