Question

Suppose you are provided with an isolated nerve-muscle preparation in order to study synaptic transmission. In one of your experiments, you give that preparation a drug that blocks voltage-gated Ca++ channels: in another , you give tetanus toxin to the preparation. How will synaptic transmission be affected in each experiment?

Answer 1

The neurotransmitters are present in the storage vesicles of the nerve terminals These are the sac like structures that are formed from Me layer pica membrane lithe action potential reach the nerve terminals, the neurotransmitters the voltage gated calcium channels are activated The influx of calcium ions causes “exocytosis," through which the stored neurotransmitters are released from the synaptic vesicles The released neurotransmitters allow the synaptic transmission, That is the transmission of impulse from one neuron to the other neuron or effectors organ via the synapse.

If the voltage gated calcium channels are closed, exocytosis do not occur Thus, the neurotransmitter release and synaptic transmission do not occur Tetanus is a neurotoxin released by the Clostridium tetani It causes muscle spa, convulsions and lock jaw in the affected people This toxin acts by inhibiting the release of acetylcholine (ACI. neurotransmitter nom the presynaptc nerve terminal of the motor neurons, which prevents the muscle depolarization and contraction process The SNAREs are the targets of neurotoxins such as botulinurn toxin and tetanus. The primary function of SNARE proteins, allow the fusion of vesicles with their target membranes. Likewise they also facilitate the fusion of synaptic vesicles that store neurotransmitter with be presynaptic membranes in neurons Thus; inhibition of SNAREs inhibits the vesicle fusion and release of neurotransmitter.