RELEASE OF RADIOACTIVE GLUTAMIC ACID FROM THIN SECTIONS OF GUINEA-PIG OLFACTORY CORTEX IN VITRO

Slices from the guinea-pig olfactory cortex were incubated in the medium containing ¹⁴C]glutamate and release of radioactive compounds was subsequently studied in the standard or high potassium media or during repetitive stimulation of the lateral olfactory tract (LOT) while electrical activity of the tissue was monitored. In 50 mm -potassium concentration, the pre- and postsynaptic potentials were completely suppressed and effluxes of total ¹⁴C and ¹⁴C]glutamate increased. No significant increase in ¹⁴C]glutamine was found. When Ca²+ concentration was reduced from 2·4 to 0·12 mm , the postsynaptic potential disappeared and release of ¹⁴C]glutamate in 50 mm -potassium decreased to about a third of that in 2·4 mm -Ca²⁺. Repetitive LOT stimulation enhanced release of total ¹⁴C in thinner slices but caused no significant increase in ¹⁴C]glutamate efflux. These findings were discussed in relation to the possibility that glutamate is a mediator between the LOT fibres and cortical neurons.