GLUTAMATE AFFECTS THE DEVELOPMENT OF THE THALAMOFUGAL VISUAL PROJECTION OF THE CHICK

Examination of the thalamofugal visual projections of the chick follow ing treatment of the hyperstriatal regions with glutamate was undertak en to investigate whether structural change underlies slowed learning known to follow such treatment. On the second day after hatching from eggs exposed to light, chicks were injected bilaterally with 5 mu l of 100 mM glutamate or physiological saline. On posthatching day 8, retr ograde fluorescence labelling of the thalamofugal projections with Tru e Blue and FluoroGold led to the labelling of thalamic cells which pro ject to the visual hyperstriatum. The number of contralateral and ipsi lateral projections relative to each dye injection site was determined . Glutamate prevented the development of the structural asymmetry whic h is present in control chicks. The resultant symmetry of the thalamof ugal projections in glutamate-treated chicks may cause deficits in vis ual discrimination. (C) 1997 Elsevier Science Ireland Ltd.