Glycine and ACh Receptors

Question 1

Define the glycine receptor.

Answer 1

• Glycine is an inhibitory neurotransmitter that is found mainly in the spinal cord. Activation of the glycine receptor causes an influx of Cl- ions, which hyperpolarizes the membrane.
• The receptor has five subunits, 3 a and 2 b. Each subunit has 4 trans-membrane domains. The b subunit is responsible for anchoring the receptor to the cytoskeleton via a protein called gephyrin. - - Glycine is particularly important in mediating inhibitory neurotransmission in the spinal cord and brainstem.
• The receptor can be activated byaalanine and taurine, in addition to glycine.
• Inhibition is produced in motor neurons by activation of either the reciprocal or recurrent pathways.

Question 2

What is Strychnine?

Answer 2

• Strychnine is a competitive antagonist of the glycine receptor.
• Strychnine causes muscular convulsions, leading to death through asphyxia.
• GABAa and glycine receptors are inhibitory ionotropic receptors that are linked to a Cl- channels.
• These receptors conform to the 5-subunit structure of the ACh nicotinic receptor, but the composition of the subunits does not mimic this receptor