Abstract
Pavlovian conditioning in Hermissenda produces a decrease in voltage-dependent (IK,A and ICa) and Ca2+-dependent (IK,Ca) currents, and an increase in the action potential (AP) duration in type B-photoreceptors. In addition, synaptic connections between B and A photoreceptors and B photoreceptor and type I interneurons are facilitated. The increase in AP duration, produced by decreasing one or more K+ currents, may account for synaptic facilitation. The present study examined this issue by using a mathematical model of the B-photoreceptor and the neurosimulator SNNAP. In the model, decreasing gK,A by 70% increased the duration of the AP in the terminal by 41% and Ca2+ influx by 30%. However, if the decrease in gK,A was combined with a decrease in gCa, similar to what has been reported experimentally, the Ca2+ influx decreased by 54%. Therefore, the concomitant change in ICa counter-acted the broadening-induced increase in Ca2+ influx in the synaptic terminal. This result suggests that a spike-duration independent process must contribute to the synaptic facilitation observed following Pavlovian conditioning.
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Flynn, M., Cai, Y., Baxter, D.A. et al. A Computational Study of the Role of Spike Broadening in Synaptic Facilitation of Hermissenda . J Comput Neurosci 15, 29–41 (2003). https://doi.org/10.1023/A:1024418701765
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DOI: https://doi.org/10.1023/A:1024418701765