Lv. Riters et Vp. Bingman, THE NMDA-RECEPTOR ANTAGONIST MK-801 IMPAIRS NAVIGATIONAL LEARNING IN HOMING PIGEONS, Behavioral and neural biology, 62(1), 1994, pp. 50-59
The present study employed the N-methyl-o-aspartate (NMDA) receptor an
tagonist MK-801 to investigate the possible importance of NMDA recepto
r activation for naturally occurring spatial learning in birds by expl
oiting the navigational ability of homing pigeons (Columba livia). Con
trol pigeons released from two unfamiliar release sites displayed vani
shing bearings that were poorly oriented. However, when released a sec
ond time from the same sites they displayed improved homeward orientat
ion. The control birds apparently learned something about the spatial
relationships of stimuli at the release sites on the first releases an
d used that information to orient better when released a second time f
rom the same locations. Experimental pigeons given the NMDA receptor a
ntagonist MK-801 (0.10 mg/g) initially behaved as controls, orienting
poorly when released for the first time from the two sites. In contras
t to controls, the experimental birds failed to show significant impro
vement in orientation when released again from the same sites without
MK-801. A second experiment revealed no state-dependent learning. Resu
lts of a position/color discrimination task showed that the impairment
s observed did not generalize to associative learning in an operant ch
amber, and together with field observations were not a result of senso
ry or motor drug effects. The data indicate that blocking NMDA recepto
rs can disrupt navigational learning in homing pigeons. As such, the r
esults are consistent with the hypothesis that NMDA receptor activatio
n plays an important role in spatial learning in birds. (C) 1994 Acade
mic Press, Inc