GABA-gated chloride ion influx in brains of tremor rats.

We measured the GABA-gated chloride ion influx and GABA concentrations in the cerebral cortex and the hippocampus of young (5 weeks old) and older (15 weeks old) tremor rats. GABA-gated chloride ion influx in these tremor rats was significantly greater than in the controls of both the 5 week- and 15 week-old groups. GABA concentrations in the cerebral cortex and hippocampus of the tremor rats increased compared with controls of 5 weeks and decreased compared with controls of 15 weeks. These findings suggest that the GABAergic presynaptic neurons in the cortex and hippocampus of the tremor rat are disturbed with aging. This change may be related to the appearance of absence-like seizures in the rats. The increased GABA-gated chloride ion influx in tremor rats may be a compensatory mechanism against the genetically-determined seizure susceptibility of these rats. Furthermore, the increased GABA levels and GABA-gated chloride ion influx found in 5 week-old tremor rats may be related to the tremor movements.