Modulation by Neurotransmitters of the Nicotinic Transmission in the Vertebrates
In the course of cholinergic nicotinic transmission, acetylcholine (ACh) is released from presynaptic membrane when an action potential arrives at the cholinergic nerve terminals. ACh released from presynaptic membrane crosses by diffusion the narrow synaptic cleft and reaches the subsynaptic membrane which is a part of postsynaptic membrane. At the subsynaptic membrane ACh binds with the nicotinic ACh receptor which is endowed with a specific and characteristic protein structure. Binding of ACh with specific binding sites of the ACh receptor induces a sudden molecular conformational change of the receptor protein, resulting in an opening of ionic channels which are imbedded in the protein structure of ACh receptor. Opening of the ionic channel causes an influx of extracellular Na+ and a simultaneous outflux of intracellular K+. Consequently, the postsynaptic ionic current (excitatory postsynaptic current; EPSC) carried by Na+ and K+ initiates the nicotinic excitatory postsynaptic potential (EPSP).
KeywordsSympathetic Ganglion Luteinizing Hormone Release Hormone Quantal Content Cholinergic Nerve Terminal Ganglionic Transmission
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