Functional NMDA and GABA(A) receptors in pioneer neurons of the cortical marginal zone

Transient pioneer neurons in the neocortical marginal zone generate an earl y corticofugal axonal projection at E12-E16 (Meyer et al., 1998). We have a nalysed the functional activity of glutamate and GABA receptors in such cel ls by measuring changes in intracellular calcium concentrations ([Ca2+](i)) . The activation of GABA(A) receptors with muscimol, as well as bath applic ation of glutamate, lead to increases in [Ca2+](i) in pioneer neurons. The stimulatory action of glutamate is mostly produced through the NMDA-type of ionotropic receptors. Metabotropic glutamate receptor activation has no ef fect on [Ca2+](i). Consistent with such results, immunocytochemical studies showed a prominent expression of GABA(A) and NMDA receptors in pioneer neu rons. The activation of such receptors may be implicated in the remodelling of pioneer neurons during development.