Measuring the impact of probabilistic transmission on neuronal output.
We have investigated the impact of stochastic transmission on the input-output relations of neurons in hippocampal slices. A synaptic input that fires a cell has a significant trial-to-trial variability in amplitude, reflecting the probabilistic release of transmitter. By measuring miniature excitatory postsynaptic currents, we estimate that synchronous release of a few vesicles can fire a CA1 cell. The firing threshold and variability can be physiologically modulated. Different cell types have distinct firing thresholds and variabilities. Long-term potentiation (LTP) decreases trial-to-trial variability. If after LTP, the stimulus is reduced to produce a threshold response, the variability returns to that observed before LTP. Thus, for a threshold input, the trial-to-trial variability is maintained with LTP. This may be important for the proper functioning of a plastic nervous system.
Otmakhov
N
N
Department of Physiology and Biophysics, University of Iowa, Iowa City 52242.
Shirke
A M
AM
Malinow
R
R
D000200:Action Potentials; D000818:Animals; D005071:Evoked Potentials / Q000187:drug effects; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D008433:Mathematics; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011336:Probability; D011712:Pyramidal Tracts / Q000502:physiology*; D051381:Rats; D013269:Stochastic Processes; D013569:Synapses / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D013779:Tetrodotoxin