Ammonia potentiates GABA sub(A) response in dissociated rat cortical neurons

The ammonium ion (NH sub(4) super(+)) evoked no response itself but facilitated the GABA-induced Cl super(-) current (I sub(Cl)) in dissociated rat cortical neurons. The GABA concentration-response curve shifted parallely to the left without changing the maximum response. Reversal potential of GABA response did not change in the presence of NH sub(4) super(+) at the concentration range between 0.1 and 1 mM. Ro 15-1788, a selective benzodiazepine receptor antagonist, did not affect the facilitatory action of NH sub(4) super(+) on GABA sub(A) receptor. The results suggest that NH sub(4) super(+) modifies the affinity of GABA sub(A) receptor for GABA, without the involvement of benzodiazepine receptors.