Veterinary Neuropharmacology

NICOTINIC RECEPTORS

• These receptors are named for their selective activation by nicotine.
• They belong to the super family of ligand-gated ion channels. Binding of acetylcholine causes rapid opening of a nonselective cation channel, which depolarises the postsynaptic or postjunctional cell.
• Nicotinic receptors are activated by nicotine and blocked by d-tubocurarine or hexamethonium.
• There are two sub types of nicotinic receptors. They are N_M and N_N receptors.
  • N_M receptors are present in the skeletal muscle motor end plate. They mediate skeletal muscle contraction. These receptors are stimulated by phenyl trimethyl ammonium and blocked by d-tubocurarine.
  • N_N receptors are present in the parasympathetic and sympathetic ganglia, adrenal medulla, spinal cord and certain areas of brain. These receptors are also stimulated by phenyl trimethyl ammonium and blocked by hexamethonium.