Cis-4-amino-crotonic acid activates alpha 6 subunit-containing GABA(A) butnot GABA(c) receptors in granule cells of adult rat cerebellar slices

The expression of GABA(C) receptors in granule cells of adult rat cerebella r slices was investigated. The GABA(C) receptor agonist cis-4-amino-crotoni c acid (CACA) evoked currents in granule cells. However, CACA-evoked curren ts were not blocked by the GABA(C) receptor antagonist (1,2,5,6-tetrahydrop yridine-4-yl)methylphosphinic acid (TPMPA), but were blocked by the GABA(A) receptor antagonist bicuculline. CACA activated alpha6 subunit-containing GABA receptors as CACA-evoked currents were reduced by furosemide and CACA activated alpha6 beta2 gamma 2s receptors expressed in HEK 293 cells. The c hannels opened by CACA had conductances which were larger than those descri bed for GABA(C) receptors but were similar to those described for GABA(A) r eceptors. GABAergic synaptic currents were blocked by low concentrations of bicuculline, but not by TPMPA. Thus, cerebellar granule cells express func tional GABA(A) but not GABA(C) receptors. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.