COBALT-PERMEABLE NON-NMDA RECEPTORS IN DEVELOPING CHICK BRAIN-STEM AUDITORY NUCLEI

KAINATE, an agonist at non-NMDA glutamate receptors, evoked strong con centration-dependent cobalt accumulation in the chick brain stem audit ory nuclei angularis, laminaris (NL) and magnocellularis (NM). This ef fect could be blocked completely by the AMPA/kainate receptor antagoni st CNQX and the AMPA antagonist GYKI 53655 but not by antagonists of N MDA receptors or voltage-sensitive calcium channels. Kainate (30 mu M) evoked cobalt uptake from embryonic day (E)9 through E21, with a peak intensity at E15. Before E13, uptake occurred mainly in NL but declin ed markedly in NM after E15 and ceased in NL by E21. We conclude that calcium-permeable non-NMDA receptors are transiently expressed at the time when mature neuronal number, form and synaptic connectivity are e stablished.