Foot shock stress decreases chloride efflux from rat brain synaptoneurosomes.

Foot shock stress delivered continuously for 20 min decreased the 36Cl- efflux from cerebral cortex synaptoneurosomes of handling-habituated (unstressed) rats but failed to have the same effect on the synaptoneurosomes of naive (stressed) rats. The presence of pentobarbital (500 microM), GABA (100 microM) or muscimol (50 microM in the dilution buffer reversed the stress-induced decrease of 36Cl- efflux from synaptoneurosomes of unstressed rats. Moreover, these drugs also stimulated 36Cl- efflux from cortical synaptoneurosomes of naive stressed rats. The results indicate that stress decreases the function of Cl- channels coupled to the GABA/barbiturate receptor complex.