Journal of Comparative Physiology A

, Volume 171, Issue 1, pp 93–104

Interactions of membrane excitability mutations affecting potassium and sodium currents in the flight and giant fiber escape systems of Drosophila

  • Jeff E. Engel
  • Chun-Fang Wu
Article
  • 124 Downloads

Summary

We have studied the influence of the K+-current mutations eag and Sh and the Na+-current mutation naptsupon two well-defined neural circuits that underlie flight and an escape response in Drosophila, recording from dorsal longitudinal and tergotrochanteral muscles. Mutations of Sh and eag affected refractory period and following frequency, but not latency, of the jump-and-flight escape response. The naptsmutation altered these 3 physiological parameters of the “jump” (TTM), but not the “flight” (DLM), branch, suggesting differences in the vulnerability of different circuit components to the mutation. In contrast to their interaction in some other systems, naptsdid not counteract the effects of eag and Sh upon these physiological parameters in eag Sh; nap triple mutants.

In eag Sh double mutants, in which multiple K+ currents may be diminished, flight muscles showed abnormal rhythmic activity not associated with flight, and some flies also had an abnormal wings-down posture. The low-frequency spikes probably originated in the flight muscle motoneurons, but the coordination between muscle fibers during this “non-flight activity” was distinct from flight. Nevertheless, in spite of the presence of this non-flight activity in resting eag Sh flies, those animals with normal wing posture were also able to fly, with a normal pattern of muscle activity. This suggests that in these mutants, the DLM motoneuron circuit is able to switch between two patterns of output, non-flight activity and flight. In eag Sh; nap triple mutants, the non-flight activity and abnormal wing posture were absent, indicating that a reduction of Na+ current counteracts the hyperexcitable influence of the K+-current mutations in this circuit.

Key words

Drosophila excitability mutants Cervical giant fiber Escape reflex Flight 

Abbreviations

CGF

cervical giant fiber

DLM

dorsal longitudinal muscle

eag

ether à go-go

FF50

following frequency with 50% response

napts

no action potential — temperature sensitive para paralytic

PSI

peripherally synapsing interneuron

Sh Shaker

TTM tergotrochanteral muscle

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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Jeff E. Engel
    • 1
  • Chun-Fang Wu
    • 1
  1. 1.Biology DepartmentUniversity of IowaIowa CityUSA

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