Quantitative Autoradiographic Demonstration of Changes in Binding to NMDA‐sensitive [3H]Glutamate and [3H]MK801, but not [3H]AMPA Receptors in Chick Forebrain 30 min After Passive Avoidance Training

Abstract

Day-old domestic chicks (Gallus domesticus) were trained on a one-trial passive avoidance task in which the aversive stimulus was an unpleasant tasting substance, methyl anthranilate. Thirty minutes later, localization of N-methyl-d-aspartic acid (NMDA)-sensitive [³H]glutamate receptor binding sites, [³H]MK801 and [³H]AMPA binding sites in 17 regions of the forebrain of methylanthranilate-trained and control (water-trained) chicks was determined using quantitative receptor autoradiography. Significant differences in binding to both MK801- and NMDA-sensitive glutamate receptors, but not α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, were found in three regions of the forebrain of trained compared to control chicks; two of these regions have been implicated from previous lesion, biochemical and morphological studies as playing a key role in the process of memory formation and storage following passive avoidance training. For NMDA-sensitive [³H]glutamate receptors, significant elevations in binding were observed in two regions, the left intermediate and medial hyperstriatum ventrale (IMHV) (39%) and the lobus parolfactorius (LPO) (34%), at 30 min post-training, but a decrease (44%) occurred in binding to the lateral neostriatum. Significant increases in binding to MK801 receptors were observed in the left IMHV (19%) and right IMHV (13%), and left LPO (22%) at 30 min post-training, though there was a decrease in the right LPO (15%). These findings, coupled with those described in a previous paper from our group (Burchuladze and Rose, Eur. J. Neurosci., 4, 533–538, 1992), demonstrate that a glutamate receptor subtype is involved in learning and memory formation in the chick.