AMPA‐evoked ion influx is strongest in tangential neurons of the rat neocortical intermediate zone close to the front of the migratory stream

In addition to the classically described radially migrating neurons, embryonic cortical areas receive neurons originating from the basal ganglia. One of the migration routes is in the intermediate zone. The front of this migration moves toward the hippocampus synchronously with the edge of the dorsally extending cortical plate. We investigated whether cells close to the front have specific properties compared with those at less advanced positions. Activation of AMPA receptors in the presence of cobalt showed that a strong influx of divalent cations could be triggered in front cells by low agonist concentration, whereas the less advanced cells needed a higher concentration to incorporate detectable amounts of cobalt. As shown by in situ hybridization, this discrepancy was not due to differential expression of GluR‐2 (known to reduce permeability for divalent cations). In vivo, release of an endogenous agonist presumably affects more, or differently, the tangential cells close to the front. Developmental Dyanmics 227:416–421, 2003. © 2003 Wiley‐Liss, Inc.