Long-term desensitization of quisqualate-specific glutamate receptors in Purkinje cells investigated with wedge recording from rat cerebellar slices.

Responses of Purkinje cells to quisqualate and aspartate were examined in rat cerebellar slices with a 'wedge' recording technique. Conditioning with bath application of 100 microM quisqualate for 1 or 4 min frequently induced reduction of Purkinje cell responses to testing bath application of 100 microM quisqualate. Test responses obtained at 5-30 min intervals were 79% after 1 min conditioning and 64% after 4 min conditioning, relative to conditioning responses. Since there was no correlation between the degree of reduction and the conditioning-testing interval, the effect of conditioning appeared to be sustained over 30 min. No such desensitization was observed with 3 or 5 mM aspartate. The presently demonstrated desensitization of quisqualate-specific glutamate receptors could represent a central mechanism of the 'long-term depression' type of synaptic plasticity in Purkinje cells.