Receptor-activated Calcium Signals in Tangentially Migrating Cortical Cells

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Abstract
Recent studies have shown that the two main types of cortical neurons, pyramidal and nonpyramidal, have different origins and use different migratory routes — radial and tangential respectively. The role of neurotransmitters in radial migration is well known; however, there are no data about their effect on intracellular calcium — [Ca2+]i — in tangentially migrating cells. We have performed ratiometric and confocal calcium imaging of 1,1′-dioctodecyl-3,3,3′,3′-tetramethylindocarbocyanine labelled tangentially migrating neurons in the intermediate zone cells of fetal rat coronal slices. Superfusion with N-methyl-d-aspartic acid (NMDA) leads to an increase in [Ca2+]i, which is blocked by the antagonist APV or the presence of Mg2+ in the medium. Kainate produced an increase in [Ca2+]i that could be blocked by the non-NMDA antagonist CNQX. Muscimol, an agonist of GABAa-receptors, produced a transitory increase in [Ca2+]i that was blocked by the specific antagonist bicuculline or the presence of tetrodotoxin in the medium. We conclude that tangentially migrating cells display consistent [Ca2+]i changes in response to agonists of NMDA, non-NMDA and GABAa receptors, suggesting that these cells are quite mature and homogeneous. The endogenous activation of these receptors may have either a direct effect on tangential migration or modulate the response of migrating cells to external cues.

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