Early in vitro development of voltage- and transmitter-gated currents in GABAergic amacrine cells.
It has been shown in previous studies that a subpopulation of neurons in monolayer cultures prepared from immature embryonic chicken retina acquired a series of functional properties which characterized them as GABAergic amacrine cells after 1 week in vitro. In the present study, we demonstrate that immature precursors of these cells were already identifiable by morphological criteria after 2 days in vitro (DIV). Using the whole cell patch-clamp technique we have studied the time-course of the expression of voltage-dependent and of glutamate and GABA receptor-associated conductances in these identified retinal interneurons developing in vitro. Recordings after 2 DIV revealed a very homogeneous pattern of membrane conductances. In all cells tested, whole cell responses to depolarizing voltage steps consisted solely of a sustained outward potassium current and 100% of the cells responded to the glutamate receptor agonist kainic acid (KA) and to GABA. Fast activating inward sodium currents first appeared after 3 DIV, whereas a transient component of outward potassium currents was not detectable before day 4 in vitro. N-Methyl-D-aspartate (NMDA)-evoked currents were first observed at 3 DIV in the GABAergic neurons. Only 1 day later they were found in all of the GABAergic neurons. Expression of responses to quisqualic acid (QU) started at 3 DIV, but remained restricted to a subpopulation of the GABAergic cells even at later stages (59% at 4 DIV, 63% at 6-9 DIV). Antagonistic effects of QU on KA responses, however, were detectable in all cells tested, independent of the developmental stage and the presence of QU-evoked currents.(ABSTRACT TRUNCATED AT 250 WORDS)
Yamashita
M
M
Max-Planck-Institute for Brain Research, Frankfurt, Germany.
Huba
R
R
Hofmann
H D
HD
D000818:Animals; D001345:Autoradiography; D002478:Cells, Cultured; D016922:Cellular Senescence; D002642:Chick Embryo; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D018698:Glutamic Acid / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology; D007395:Interneurons / Q000166:cytology / Q000502:physiology; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007608:Kainic Acid / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D016318:Quisqualic Acid / Q000494:pharmacology; D018079:Receptors, GABA / Q000502:physiology*; D017470:Receptors, Glutamate / Q000502:physiology; D012160:Retina / Q000166:cytology / Q000502:physiology*; D013997:Time Factors; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000494:pharmacology*
D007473:Ion Channels; D018079:Receptors, GABA; D017470:Receptors, Glutamate; D014316:Tritium; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D016318:Quisqualic Acid; D007608:Kainic Acid; D005998:Glycine