GABA(B)-ergic modulation of burst rate and intersegmental coordination in lamprey: experiments and simulations.

Neuromodulators which influence the operation of neural networks act as a rule via several cellular and synaptic mechanisms. Activation of GABA(B)-receptors in the lamprey spinal cord reduce both calcium currents and the peak amplitude of the post-spike afterhyperpolarization (AHP). Activation of GABA(B)-receptors reduce the segmental alternation rate and modifies the intersegmental coordination when the spinal locomotor circuits are activated by NMDA. Using physiological experiments we find that a reduced AHP is not sufficient to account for the observed reduction of the burst rate. Computer simulations revealed that either a reduced AHP or calcium current could alter the phase coordination between the segments similar to earlier experiments.