Effects of syntropan, atropine and scopolamine on uptake of GABA by homogenates of rat cerebrum

The brain tissue has a specific uptake process for GABA and this may provide an effective mechanism for terminating its inhibitory action on neurons. Thus, it is possible that some drugs might produce their effects by blocking the uptake of GABA after its release from nerve endings. In the present investigation we determined the effects of 3 anticholinergic drugs and flurazepam on uptake of GABA with a quantitative analysis for the uptake of [3H]GABA by homogenates of rat cerebrum. At a concentration of 0.1 mmol/L, atropine and scopolamine had only small inhibitory effect reducing the uptake of [3H]GABA to 62%, but syntropan (IC50 5 micromol/L) was more potent inhibitor than flurazepam (IC50 120 micromol/L) in vitro. After ip of syntropan (2.5 mg/kg) or flurazepam (25 mg/kg), the rat cerebral homogenates showed significantly lower (P<0.01) uptake of [3H]GABA as compared with the control.