Stimulation of 36Cl- influx into rabbit cerebral cortex microsacs by the endogenous antigen S-100

The rate of accumulation of 36Cl- ions into rabbit cerebral cortex microsacs has been studied under various conditions. Such a parameter is increased by 164% by 10(-4) M GABA, the effect being reversed in the presence of 10(-4) M bicuculline and 10(-4) M picrotoxin. Incorporation of the endogenous antigen S-100, by a preincubation of the fraction with the protein in the presence of 2.5 mM Ca++, brings about a 56% stimulation of 36Cl- influx rate. This effect does not seem to be additive with that of GABA. The S-100 effect is reversed by picrotoxin but not by bicuculline. The overall pattern of data suggests an action of the antigen directly at the GABAA receptor complex and in particular at the GABA activated Cl- channel.