EARLY ISOLATION FROM CONSPECIFIC SONG DOES NOT AFFECT THE NORMAL DEVELOPMENTAL DECLINE OF N-METHYL-D-ASPARTATE RECEPTOR-BINDING IN AN AVIANSONG NUCLEUS

Early effects of experience on synaptic reorganization and behavior of ten involve activation of N-methyl-D-aspartate (NMDA) receptors. We ha ve begun to explore the role of this glutamate-receptor subtype in the development of learned birdsong. Song learning in zebra finches occur s during a restricted period that coincides with extensive synaptic re organization within neural regions controlling song behavior. In one b rain region necessary for song learning, the lateral magnocellular nuc leus of the anterior neostriatum (IMAN), NMDA receptor binding is twic e as high at the onset of song learning as in adulthood. In the presen t study, we used quantitative autoradiography with the noncompetitive NMDA antagonist [H-3]MK-801 to examine more closely the developmental decline in NMDA receptor binding within IMAN and found that it occurre d gradually over the period of song learning and was not associated wi th a particular stage of the learning process. In addition, early isol ation from conspecific song did not affect [H-3]MK-801 binding in IMAN at 30, 60, or 80 days. Since behavioral studies confirmed that our is olate rearing conditions extended the sensitive period for song learni ng, we conclude that the normal developmental decline in overall NMDA receptor binding within IMAN does not terminate the capacity for song learning. Finally, early deafening, which prevents both stages of song learning, also did not affect [H-3]MK-801 binding in IMAN at 80 days, indicating that the decline in NMDA receptor binding occurs in the ab sence of auditory experiences associated with song development. (C) 19 95 John Wiley and Sons, Inc.