PHYSIOLOGY
SYNAPTIC PHYSIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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have most of its effects on the dendritic region of a neuron
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increase the release of neurotransmitter molecules
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prevent the depolarization phase of the action potential
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prevent graded potentials
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Detailed explanation-1: -Tetrodotoxin (TTX ) is a potent toxin that specifically binds to voltage gated sodium channels. TTX binding physically blocks the flow of sodium ions through the channel, thereby preventing action potential (AP) generation and propagation.
Detailed explanation-2: -Batrachotoxin, grayanotoxins, veratridine and aconitine alter the kinetics and voltage dependence of sodium channel activation and inhibit sodium channel inactivation through binding to neurotoxin receptor site 2.
Detailed explanation-3: -Both hydrophilic low molecular weight toxins and larger polypeptide toxins physically block the pore and prevent sodium conductance. Hydrophobic alkaloid toxins and related lipid-soluble toxins act at intramembrane sites and alter voltage-dependent gating of sodium channels via an allosteric mechanism.
Detailed explanation-4: -The interaction between neurotoxins and VGSCs can occur in two different ways. It either results in a pore block when the toxin physically occludes the pore and thereby inhibits the sodium conductance, or in a modification of the gating, which leads to altered gating kinetics and voltage-dependence of the channels.
Detailed explanation-5: -1 Tetrodotoxin and Saxitoxin. The naturally occurring marine toxins tetrodotoxin (TTX) and saxitoxin (STX) interact strongly with the Nav channel pore region to occlude the Na+ permeation pathway (Fig. 1) (Hille 1975).