Developmental changes of inward rectifier currents in neurons of the rat entorhinal cortex

A slice preparation was used to investigate inward rectifier currents (I(H)) of entorhinal cortex (EC) neurons. Using the whole-cell configuration of the patch-clamp technique, I(H) was studied in pyramidal cells from layer IV of the rat EC and in stellate cells from layer II of the EC. Inward rectifier currents were analyzed in neurons of newborn (P1-3), juvenile (P8-14) and adult (>P28) rats. Pyramidal cells of juvenile rats possessed a significantly larger current density of I(H) than pyramidal cells of newborn rats, whereas no differences in the current density of I(H) were found between pyramidal neurons of juvenile and of adult animals. In contrast, the current density of I(H) of stellate cells was significantly increased in juvenile rats compared with newborn rats as well as in adult rats compared with juvenile rats. Moreover, in adult rats the current density of I(H) was larger in stellate cells than in pyramidal cells, whereas opposite data were obtained in juvenile animals.