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GABAa Receptors are Excitatory During Embryogenesis

NEURO-KNDEXW

In an adult brain, the neurotransmitter GABA is inhibitory. When neurons are stimulated with GABAa receptor agonists, it causes the opening of the GABAa receptor coupled chloride channels and hyperpolarization.

Interestingly, in the embryonic brain, GABA is an excitatory neurotransmitter. When GABAa receptor agonists are applied to embryonic neurons, it causes their depolarization.

What happens during development that causes GABA to switch from excitation to inhibition?

A

Embryonic neurons do not express GABAa receptors.

B

GABAa receptor associated ion channels switch permeability from $Na^+$ to $Cl^-$ ions during development.

C

The $Cl^-$ gradient across the plasma membrane changes during development from low intracellular chloride in embryonic neurons to high intracellular and low extracellular chloride in mature neurons.

D

The $Cl^-$ gradient across the plasma membrane changes during development from high intracellular chloride in embryonic neurons to low intracellular and high extracellular chloride in mature neurons.