Some properties of membrane current fluctuations induced by kainate, quisqualate, and NMDA in cultured septal neurons of rat.

Ionic currents induced by glutamate, kainate, quisqualate, and N-methyl-D-aspartate (NMDA) in cultured septal neurons were analyzed by fluctuations analysis. The power spectrum (PWS) of NMDA current fluctuations always fitted a single Lorentzian. PWSs of the other agonists fitted the sum of two Lorentzians; however, the slopes of PWSs became larger and the PWSs became closer to single Lorentzians as the number of drug application increased. This may be explained in such a way that, in multiple conductance channels activated by these agonists, the high frequency component decreases the gating activity in later recordings, whereas the low frequency component keeps its gating kinetics.