Furosemide increases the basal tert -[ 35 S]butylbicyclophosphorothionate ([ 35 S]TBPS) binding and reverses the inhibition of the binding by ␥ -aminobutyric acid (GABA) in the cerebellar GABA A receptors containing the ␣ 6 and  2/  3 subunits. These effects are less pronounced in the alcohol-sensitive (ANT) than in the alcohol-insensitive (AT) rat line. The difference between the rat lines in the increase of basal [ 35 S]TBPS binding was removed after a longer preincubation with ethylendiaminetetraacetic acid (EDTA) containing buffer, but long preincubation did not reduce the GABA content of the incubation fluid or remove the difference in GABA antagonism by furosemide. The GABA sensitivity of the [ 35 S]TBPS binding did not differ between the rat lines. There was no nucleotide sequence difference in the  2 or  3 subunits between the rat lines and similar  2/3 subunit-dependent agonistic actions by methyl-6,7-dimethoxy-4-ethyl- -carboline-3-carboxylate (DMCM) in the rat lines were detected. The data suggest that there are still unknown structural alterations in the cerebellar GABA A receptors between the AT and ANT rat lines, possibly associated with differential alcohol sensitivity.