Mechanisms underlying the activity-dependent regulation of locomotor network performance by the XXXX pump.

@entity6193 @entity3529 @entity4024 @entity1238 @entity1372 @entity7832
Activity-dependent modification of neural network output usually results from changes in neurotransmitter release and/or membrane conductance. In @entity1238 frog tadpoles, spinal locomotor network output is adapted by an ultraslow afterhyperpolarization (usAHP) mediated by an increase in @entity4024 pump current. Here we systematically explore how the interval between two swimming episodes affects the second episode, which is shorter and slower than the first episode. We find the firing reliability of spinal rhythmic neurons to be lower in the second episode, except for excitatory descending interneurons (dINs). The @entity1372 /proton antiporter, @entity6193 , which potentiates @entity4024 pump function, induced similar effects to short inter-swim intervals. A usAHP induced by supra-threshold pulses reduced neuronal firing reliability during swimming. It also increased the threshold current for spiking and introduced a delay to the first spike in a train, without reducing subsequent firing frequency. This delay was abolished by @entity7832 or zero @entity3529 saline, which eliminate the usAHP. We present evidence for an A-type @entity3529 current in spinal CPG neurons which is inactivated by depolarization and de-inactivated by hyperpolarization, and accounts for the prolonged delay. We conclude that the usAHP attenuates neuronal responses to excitatory network inputs by both membrane hyperpolarization and enhanced de-inactivation of an A-current.
