Presynaptic inhibition differs from postsynaptic inhibition primarily because it:

• A Hyperpolarizes the soma of the target neuron via opening chloride channels
• B Requires uptake of the neurotransmitter by astrocytes before it can act
• C Involves direct electrical coupling between the inhibiting and inhibited axons
• D Reduces transmitter release from the terminal by acting through an axo-axonic synapse ✓

Explanation

In presynaptic inhibition an inhibitory interneuron forms an axo-axonic synapse on the excitatory terminal. Activation of receptors there (classically GABA-D) closes presynaptic calcium channels and opens potassium channels, reducing calcium influx and thus reducing transmitter release. The postsynaptic membrane potential is unchanged, which distinguishes it from postsynaptic inhibition, where IPSPs hyperpolarize or shunt the soma and dendrites.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.