Blockage of one class of potassium channel alters the effectiveness of halothane in a brain circuit of Drosophila

At concentrations comparable to those used in the clinic, halothane has pro found effects on a neuronal pathway devoted to the escape reflex of the fru it fly, Drosophila melanogaster. We studied the influence of the potassium channel that is encoded by the Shaker gene on the halothane sensitivity of this circuit. Shaker channels were specifically inactivated either by genet ic means, using strains with two different severe Shaker mutations, or by p harmacologic means, using ingestion of millimolar concentrations of 4-amino pyridine. In all cases, halothane potency decreased substantially. To ensur e that the genetic alteration was specific, both mutations were studied as stocks that had been repeatedly backcrossed to a control strain. The specif icity of the pharmacologic inhibition was demonstrated by the fact that Cam inopyridine had no effect on halothane potency in a Shaker mutant. Quantita tive differences in the effects of channel inhibition between males and fem ales suggested a sexual dimorphism in the functional brain anatomy of the r eflex circuit.