Q.18

The receptors for gamma amino butyric acid (GABA) in humans are

(A) ligand gated chloride ion channels

(B) ligand gated sodium ion channels

(C) ligand gated potassium ion channels

(D) ligand gated calcium ion channels

GABA Receptors in Humans: Ligand-Gated Chloride Channels Explained

GABA receptors primarily refer to GABA_A receptors, which function as ligand-gated chloride ion channels in humans. The correct answer to the multiple-choice question is (A) ligand gated chloride ion channels.

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Correct Answer

GABA_A receptors, the main fast-acting GABA receptors, open chloride-selective pores upon GABA binding, leading to hyperpolarization and inhibition of neuronal firing. This chloride influx stabilizes the membrane potential near -75 mV, countering excitatory signals.

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Option Analysis

• (A) Ligand gated chloride ion channels: Accurate for GABA_A receptors, pentameric structures that mediate rapid synaptic inhibition via Cl⁻ conductance.

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• (B) Ligand gated sodium ion channels: Incorrect; sodium channels like nicotinic receptors depolarize cells, opposite to GABA’s inhibitory role.

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• (C) Ligand gated potassium ion channels: Incorrect; while GABA_B receptors indirectly activate K⁺ channels via G-proteins, they are metabotropic, not ligand-gated.

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• (D) Ligand gated calcium ion channels: Incorrect; no GABA receptors directly gate Ca²⁺ ions, which would promote excitation rather than inhibition.