Role of slowpoke calcium-dependent potassium channels in shaping rhythmic locomotor activity in Drosophila larvae
Rhythmic motor behaviors are generated by networks of neurons. The sequence and timing of muscle contractions depends on both synaptic connections between neurons and the neurons’ intrinsic properties. In particular, motor neuron ion currents may contribute significantly to motor output. Large conductance Ca2+ -dependent K+ (BK) currents play a role in action potential repolarization, interspike interval, repetitive and burst firing, burst termination and interburst interval in neurons. Mutations in slowpoke (slo) genes encoding BK channels result in motor disturbances. This study examined the role of slo channels in shaping rhythmic motor activity using Drosophila larva as a model system. Dual intracellular recordings from adjacent body wall muscles were made during spontaneous crawling-related activity in larvae expressing genetic manipulations of slo expression. The incidence and duration of rhythmic activity in slo mutants were similar to wild-type control animals, while the timing of the motor pattern was altered. slo mutants showed decreased burst durations, cycle durations, and quiescence intervals, and increased duty cycles, relative to wild-type. A slo RNA interference construct was expressed in identified motor neurons, and phenocopied many of the effects observed in the mutant, including decreases in quiescence interval and cycle duration. Overall, these results suggest an important role for slo channels in the whole larva, and specifically in motor neurons, in determining the frequency of crawling activity. This study also highlights the importance of motor neuron intrinsic properties in shaping the timing of motor output.
Updated June, 2013: A peer-reviewed and revised version of this manuscript has been published. Please refer to: McKiernan, E.C. (2013). Effects of manipulating slowpoke calcium-dependent potassium channel expression on rhythmic locomotor activity in Drosophila larvae. PeerJ 1:e57.
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