Involvement of post-synaptic kainate receptors during synaptic transmission between unitary connections in rat neocortex.
The properties of functional kainate receptor-mediated EPSCs were studied in acute slices from 19-35-day-old rats. EPSCs elicited in pyramidal and fast-spiking cells in layers 2/3 and 5 of the rat motor cortex by extracellular single shock stimulus in the presence of GYKI 53655 and D-2-amino-5-phosphopentanoic resulted in a residual current. This current was not enhanced by cyclothiazide but was blocked by 6-cyano-7-nitroquinoxalin-2,3-dione and is thought to be mediated by kainate receptors. These kainate receptor-mediated currents displayed a wide range of time courses depending on which pre-synaptic fibres were activated. With paired recordings, unitary EPSCs elicited in pyramidal cells were almost totally blocked by GYKI 53655 and D-2-amino-5-phosphopentanoic. However, when L-transpyrrolidine-2,4-dicarboxylate (PDC), a glutamate uptake blocker, was introduced in the bath, the amplitude of kainate receptor-mediated currents, which is resistant to GYKI 53655 and D-2-amino-5-phosphopentanoic, was revealed. The rise and decay time constants of the kainate receptor-mediated currents were identical to control EPSCs. PDC was not required to reveal the kainate receptor-mediated currents elicited in fast-spiking cells which also displayed similar rise and decay time constants to the control EPSCs. Excitatory input onto pyramidal and fast-spiking cells in the neocortex mediated by kainate receptors contributed between 14 and 40% of the total control unitary EPSCs which displayed identical time courses to the AMPA receptor-mediated component of the EPSCs. Post-synaptic kainate receptors at connected pyramidal cell synapses may be located extra-synaptically.
Ali
Afia B
AB
University Laboratory of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK. afia.ali@physiol.ol.ac.uk
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology; D001581:Benzothiadiazines / Q000494:pharmacology; D003998:Dicarboxylic Acids / Q000494:pharmacology; D004347:Drug Interactions; D004553:Electric Conductivity; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D019579:Neocortex / Q000166:cytology / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018092:Kainic Acid Receptors / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D013997:Time Factors; D014633:Valine / Q000031:analogs & derivatives* / Q000494:pharmacology
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000959:Antihypertensive Agents; D001569:Benzodiazepines; D001581:Benzothiadiazines; D003998:Dicarboxylic Acids; D018691:Excitatory Amino Acid Antagonists; D014179:Neurotransmitter Uptake Inhibitors; D011759:Pyrrolidines; D018092:Kainic Acid Receptors; D014633:Valine; C079692:GYKI 53655; C056639:2-amino-5-phosphopentanoic acid; C083486:pyrrolidine-2,4-dicarboxylic acid; C004639:cyclothiazide