Question

Explain Pre-synaptic modulation and give at least one example of where it is used in the nervous system.

Answer 1

ANSWER) Any process, acting in the presynapse that is near axon terminal of neuron and results in modulation of chemical synaptic transmission is called Pre-Synaptic modulation.

• Presynaptic modulation can be excitatory or inhibitory.
• There are two types :-

1. Pre-Synaptic Facilitation - The release of neurotransmitter is enhanced.
2. Pre-Synaptic Inhibition - The release of neurotransmitter is inhibited

EXAMPLES

• It is used in the cortex, axon terminals of interneurons release gamma amino butyric acid (GABA) onto their synaptic targets, where the inhibitory action can compete with the excitatory forces brought about by the principal cells.
• However, inhibitory interneurons do much more than just provide stop signals for excitation. Proper dynamics in neuronal networks can only be maintained if the excitatory forces are counteracted by effective inhibitory forces.
• The presynaptic facilitation has been shown to be simulated by serotonin and by cyclic AMP and to be accompanied by an increase in the Ca2+ current of sensory neuron cell bodies.

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