Nicotinic Receptor
| Overview |
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- Nictotinic Receptors bind acetylcholine and are located in the CNS, autonomic ganglia, and at the neuromuscular junction. They take their name from the fact that they specifically bind Nicotine with only mild affinity for Muscarine. These receptors are ion channels and acetylocholine binding leads to direct opening of sodium channels and thus depolarization of the neuron.
| Mechanism of Action |
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- Nictonic Receptors are ligand-gated sodium channels. Binding of two acetylcholine molecules leads to opening of the ion channel and intracellular entry of sodium, leading to depolarization of the neuron and thus its excitation.
| Locations |
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- Central Nervous System: Nictonic receptors play a prominent role in the CNS and are involved in attention and memory. Defects in these pathways appear to play a role in Alzheimer Disease.
- Autonomic Ganglia: All autonomic ganglia, both those of the sympathetic and parasympathetic nervous system, possess nicotinic receptors on their post-ganglionic neurons (See: Physiological Anatomy section of autonomic nervous system)
- Adrenal Medulla: Catecholamine-secreting adrenomedullary chromaffin cells possess nicotinic receptors that are activated by sympathetic fibers.
- Neuromuscular Junction: The neuromuscular endplate possess high concentrations of nicotinic receptors that are activated by motor neurons, resulting in muscular depolarization and consequently contraction.
| Subtypes |
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- Two distinct subtypes of nicotinic receptors exist at autonomic ganglia and the neuromuscular junction. These subtypes can be blocked by distinct drugs, allowing for specific pharmacological inhibition.