Electrophysiological properties of lamprey spinal neurons during fictive locomotion
Specific electrophysiological properties of lamprey spinal neurons change when the neurons go from a quiescent state to an active state of fictive locomotion. These changes include a tonic reduction of the slow AHP and the slope of the F-I relationship in motor-related cell types (the F-I relationship slope was either increased or showed no change in sensory-related cell types). A decreased rheobase in motor-related cells was linked to the depolarizing phase of the locomotor activity. Some properties such as spike threshold and the action potential characteristics showed no change in any cell type. The reduction of the F-I slope and the slow AHP amplitude observed in fictive locomotion could be reproduced by adding serotonin or removing calcium from the bath. This suggests that these properties may be altered during locomotion by serotonin acting through a reduction in calcium currents. Spiperone, a serotonergic antagonist in lamprey, increased the slow AHP amplitude and the F-I slope (though the slope showed only a 10% return and the difference was not significant) during fictive swimming, suggesting that serotonin is partially responsible for these changes during swimming. The swim rhythm was also less stable in the presence of spiperone, indicating that the release of serotonin during network activity may serve to stabilize the network. In reducing the F-I slope, the output of a neuron is less affected by differences in synaptic input. Thus, the network may be stabilized because its neurons are less responsive to small perturbations in synaptic input.
Michelle Marie Dacus,
"Electrophysiological properties of lamprey spinal neurons during fictive locomotion"
(January 1, 2000).
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