N1 - Nicotinic Receptors (Ach)(neuronal)

Schematic diagram of the N1-nicotinic (neuronal/ganglionic) ligand-gated ion channel receptor..
The receptor is composed of five subunits, each with four transmembrane spanning elements. The large extracellular N-terminal region forms the binding sites for acetylcholine (Ach) and other nicotinic agonists and antagonists. Binding of two Ach molecules causes a rapid (ms) opening of the sodium channel. Na+ flows down its concentration gradient into the cell causing depolarization and an exitatory postsynaptic potential (EPSP). This can lead to an action potential and propagation of the exitatory signal by firing of the postsynaptic connection. N1-nicotinic receptors are found in both sympathetic and parasympathetic autonomic ganglia and in the adrenal medulla.
N2-nicotinic receptors act in a similar fashion but are found at the neuromuscular junction of skeletal muscle.
N1-nicotinic receptors cause depolarization of ganglia in the following manner:

• Autonomic Ganglia: firing of postsynaptic connection for both sympathetic and parasympathetic neurons.
• Adrenal medulla: secretion of epinephrine

Adapted from Figure 2-12: StatRef Online Library: Basic and Clinical Pharmacology 8th ed. (2001)
by Michael Bolger, 8/26/01
Copyright(c) 2001 The McGraw Hill Companies, Inc. All rights reserved