Presynaptic frequency filtering in the gamma frequency band; dual intracellular recordings in slices of adult rat and cat neocortex.
Using dual intracellular recordings in slices of adult rat and cat neocortex, the frequency-filtering characteristics of 'depressing' synapses made by pyramidal axons at interspike intervals between 5 and 50 ms were studied. At 'depressing' connections from excitatory cells to some inhibitory interneurons (n = 6), recovery from short interspike interval depression was near exponential. Extrapolation of exponentials fitted to this recovery demonstrated a residual 10-20% depression at intervals >50 ms. This slowly decaying component was larger for later excitatory postsynaptic potentials (EPSPs) in trains which were typically more strongly depressed. At >80% of connections between spiny excitatory cells and at pyramid to parvalbumin-immunopositive interneuron connections, however, recovery exhibited a more complex time course. A narrow 'notch' (half-width 5 ms), peaking at intervals of 13-25 ms during which the EPSP was depressed further, interrupted recovery from short interval depression. This 'notch' was equally apparent for all EPSPs in brief trains and was mediated presynaptically.
Thomson
Alex M
AM
Department of Physiology, Royal Free and University College Medical School, Rowland Hill Street, London NW3 2PF, UK. alext@ucl.ac.uk
West
David C
DC
D000200:Action Potentials; D000818:Animals; D001369:Axons / Q000502:physiology; D002415:Cats; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials; D007395:Interneurons / Q000737:chemistry / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials; D019579:Neocortex / Q000502:physiology*; D010320:Parvalbumins / Q000032:analysis; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission; D013997:Time Factors
D010320:Parvalbumins