Nerve Terminal Excitability and Neuromuscular Transmission inT(X;Y)V7andShakerMutants ofDrosophila Melanogaster

Abstract
We investigated the neuromuscular transmission in relation with genetic neuronal excitability changes in mutants T(X;Y)V7 and ShKS133 of Drosophila. These mutations affect two different genes belonging to the Shaker gene complex which encode different yet functionally related proteins. Experiments were performed on neuromuscular junctions from Drosophila larvae by recording pre- and postsynatic membrane currents using external electrodes. It was found that the neuromuscular electrophysiological phenotype of T(X;Y)V7 is caused by presynaptic membrane hyperexcitability probably in relation with a Ca2+-dependent down regulation of voltage dependent K channels. By contrast, the ShKS133 phenotype can be explained solely by action potential widening due to the absence of type-A K channels.

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