PMID- 8389834
OWN - NLM
STAT- MEDLINE
DCOM- 19930715
LR  - 20220310
IS  - 0022-3077 (Print)
IS  - 0022-3077 (Linking)
VI  - 69
IP  - 5
DP  - 1993 May
TI  - Two modes of interspike interval shortening by brief transient depolarizations in 
      cat neocortical neurons.
PG  - 1661-72
AB  - 1. The effects of small, brief depolarizing pulses and excitatory postsynaptic 
      potentials (EPSPs) on neuronal firing were examined in layer V neurons in slices 
      of cat sensorimotor cortex. During intracellular recording, brief depolarizing 
      current pulses (duration, 0.5-2.0 ms; amplitude, 0.1-4.0 nA) were injected in 
      neurons to produce pulse potentials (PPs) with a near-linear rise to a peak 
      (0.08-3.6 mV; rise time = pulse duration) followed by an exponential decay. These 
      PPs resembled EPSPs evoked by electrical stimulation of adjacent sites. When 
      injected in neurons that were induced to discharge tonically, the PPs shortened 
      the interspike intervals (ISIs) in two ways, depending on their time of arrival 
      in the ISI. 2. Toward the end of the ISI, the PPs crossed a time-varying firing 
      level, thereby directly evoking action potentials and shortening the ISIs. These 
      directly evoked spikes occurred during the rise or peak of the PPs. The absolute 
      firing level increased with the membrane trajectory during the latter part of the 
      ISI. 3. PPs that appeared earlier in the ISI did not cross firing level directly 
      but could nevertheless shorten the ISI by a slow regenerative process. The 
      indirectly evoked spikes occurred after the peak of the PPs, at latencies whose 
      magnitude and variability increased as the PPs appeared at successively earlier 
      times in the ISI. PPs that occurred during the initial portion (approximately the 
      1st 3rd) of the ISI did not affect ISI duration. 4. Stimulus-evoked EPSPs 
      shortened the ISIs in a manner similar to that of PPs. Like PPs, EPSPs caused 
      direct crossings late in the ISI and indirect crossings earlier. Comparison of 
      the mean and maximum ISI shortenings and the range of delays in which the PPs and 
      EPSPs consistently produced ISI shortenings revealed no systematic differences. 
      These similarities suggest that PPs may be used to simulate the ISI shortenings 
      caused by EPSPs. 5. To characterize possible mechanisms underlying the ISI 
      shortening, we examined the PP shapes at different times in the ISI. PPs 
      immediately following a spike were smaller and decayed more rapidly than those 
      evoked by the same current at rest. Late in the ISI, when the membrane potential 
      was > 5 mV above rest, the PP height exceeded that of the PP at rest. This 
      amplitude increase may be due to activation of the persistent sodium 
      current.(ABSTRACT TRUNCATED AT 400 WORDS)
FAU - Reyes, A D
AU  - Reyes AD
AD  - Department of Physiology and Biophysics, University of Washington, Seattle 98195.
FAU - Fetz, E E
AU  - Fetz EE
LA  - eng
GR  - NS-12542/NS/NINDS NIH HHS/United States
GR  - RR-00166/RR/NCRR NIH HHS/United States
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - J Neurophysiol
JT  - Journal of neurophysiology
JID - 0375404
SB  - IM
MH  - Animals
MH  - Cats
MH  - Computer Simulation
MH  - Culture Techniques
MH  - Electric Stimulation
MH  - Evoked Potentials, Somatosensory/*physiology
MH  - Female
MH  - Male
MH  - Neurons/physiology
MH  - Reaction Time/*physiology
MH  - Somatosensory Cortex/*physiology
MH  - Synapses/*physiology
MH  - Synaptic Transmission/*physiology
EDAT- 1993/05/01 00:00
MHDA- 1993/05/01 00:01
CRDT- 1993/05/01 00:00
PHST- 1993/05/01 00:00 [pubmed]
PHST- 1993/05/01 00:01 [medline]
PHST- 1993/05/01 00:00 [entrez]
AID - 10.1152/jn.1993.69.5.1661 [doi]
PST - ppublish
SO  - J Neurophysiol. 1993 May;69(5):1661-72. doi: 10.1152/jn.1993.69.5.1661.