Barbiturate and picrotoxin‐sensitive chloride efflux in rat cerebral cortical synaptoneurosomes

The effects of various barbiturates and picrotoxin in modifying the efflux of chloride (36Cl−) was studied in a novel subcellular preparation from rat cerebral cortex, the ‘synaptoneurosome’. Dilution of synaptoneurosomes pre‐loaded with 36Cl− resulted in rapid efflux of 36Cl− that could be measured as early as 10 s following dilution. In the presence of barbiturates such as pentobarbital and hexobarbital there was a significant increase in 36Cl− efflux which was not observed with the pharmacologically‐inactive barbiturate, barbital. The effect of barbiturates in enhancing 36Cl− efflux was also stereospecific [(−)‐DMBB > (+)‐DMBB] and reversed by picrotoxin. By contrast, picrotoxin alone significantly inhibited 36Cl− efflux. These data demonstrate pharmacologically relevant Cl− transport for the first time in a subcellular brain preparation.