BLOCKADE OF NMDA RECEPTORS DURING SONG MODEL EXPOSURE IMPAIRS SONG DEVELOPMENT IN JUVENILE ZEBRA FINCHES

Juvenile zebra finches (Poephila guttata) learn their courtship song b y memorizing and then reproducing the song of an adult male. Several b rain regions involved in song behavior contain N-methyl-D-aspartate (N MDA) receptors, and within one brain nucleus necessary for normal song development, the density of these receptors is twice as high in juven iles that are learning song then in adults that can no longer modify t heir songs. To determine whether NMDA receptor activation is necessary for normal song development, juvenile zebra finches were systemically injected with the NMDA receptor antagonist MK-801 (0.1 mg/kg) before exposure to an adult male tutor. One control group received the same n umber of MK-801 injections 24 h out of phase with tutoring, and anothe r received saline before tutoring. In adulthood, birds given MK-801 be fore tutoring showed little evidence of learning from the tutor, and t heir songs contained abnormal syllables typical of untutored birds. In contrast, all control birds developed normal songs and copied an aver age of 72.5% of the tutor's syllables. Acute injections of MK-801 did not alter auditory brainstem evoked potentials in juveniles, indicatin g that the behavioral effects of MK-801 on song learning were not due to temporary hearing loss. Our results suggest that normal song develo pment in juvenile zebra finches requires NMDA receptor activation duri ng song model presentation. (C) 1996 Academic Press,Inc.