N-ethylmaleimide selectively blocks presynaptic GABA-B autoreceptor but not heteroreceptor-mediated inhibition in adult rat striatal slices.

Intracellular recording techniques were used in slices of adult rat striatum to compare the sensitivity of presynaptic gamma-aminobutyric acid type B (GABA-B) autoreceptor and heteroreceptor-mediated inhibition to the sulfhydryl alkylating agent, N-ethylmaleimide (NEM). NEM (100 microM) alone had no significant effect on resting potential or input resistance and did not consistently effect stimulus-evoked responses. Treatment of slices with NEM for up to 1 h, either in the presence or the absence of the GABA-B receptor-specific agonist, baclofen (BAC; 100 microM), completely blocked the BAC-induced depression of inhibitory, but not excitatory, postsynaptic potentials. This differential sensitivity to NEM alkylation suggests that in the adult rat striatum, the presynaptic GABA-B autoreceptors and heteroreceptors may exhibit distinct receptor-effector coupling mechanisms.