Properties of glutamate-gated ion channels in horizontal cells of the perch retina.
The effect of two different concentrations of L-glutamate and kainate on the gating kinetics of amino acid-sensitive non-NMDA channels were studied in cultured teleost retinal horizontal cells by single-channel recording and by noise analysis of whole-cell currents. When the glutamate agonist kainate was applied clearly parabolic mean-variance relations of whole-cell membrane currents (up to 3000 pA) indicated that this agonist was acting on one type of channels with a conductance of 5-10 pS. The cells were less sensitive when L-glutamate was used as the agonist and in most cases whole-cell currents amounted to less than 200 pA. The mean-variance relation of glutamate induced currents was complex, indicating that more than one type of channel opening could be involved. Power spectra of whole-cell currents were fitted with two Lorentzians with time constants of approx. 1 and 5-20 msec. Effects on amplitudes and time constants of agonist concentrations are demonstrated. Two categories of unitary events with mean open times of approx. 1 and 7 msec and conductances of approx. 7 and 12 pS, respectively, were obtained in single-channel recordings from cell-attached patches at different concentrations of glutamate in the pipette.
Schmidt
K F
KF
Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany. karl.f.schmidt@physiologie.med.uni-giessen.de
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005971:Glutamates / Q000378:metabolism* / Q000494:pharmacology; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism*; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D010471:Perches / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000378:metabolism*
D005971:Glutamates; D007473:Ion Channels; D007608:Kainic Acid