Abstract
Cajal-Retzius cells locating in marginal zone (MZ) play important roles in the construction of the cerebral cortex. In cortical plate, Ca2+ influx induced by GABAA receptor- and/or glycine receptor-mediated depolarization is associated with cell migration and synapse formation. However, the roles of GABAA receptor- and glycine receptor-mediated responses in synaptic transmission of MZ are yet to be elucidated. Tangential slices were made from MZ of postnatal 0-3 rats. Spread of excitation was recorded by voltage imaging using voltage-sensitive dye, JPW1114. Action potentials evoked by single electric stimuli radially spreaded over surrounding MZ, and those spread of excitation were completely blocked by tetrodotoxin or Ca2+-free medium. Although they were hardly affected by glutamate receptor blockers, AP5 and CNQX, GABAA receptor antagonists, bicuculline and picrotoxin, and glycine receptor antagonist, strychnine largely inhibited them. Furthermore, Na+,K+-2Cl− cotransporter inhibitor, bumetanide, also reduced spread of excitation in the MZ. Our data suggest that the high intracellular Cl− concentration maintained mainly by NKCC1 is attributable to the excitatory roles of GABA and glycine receptor agonists, in the synaptic transmission of the MZ. Either synaptic or no-synaptic release of those "excitatory" amino acids were further analysed by using microdyalysis technique. [Jpn J Physiol 54 Suppl:S146 (2004)]
