Figure 3.—
Neuronal expression esgEP raises the seizure threshold of eas flies. (A) A seizure is elicited in an eas sibling control fly (genotype eas; +/CyO; elav-GAL4/+) by a high-frequency stimulus of low strength (8 V). The HF stimulus (box) is a short wave train (0.5-ms pulses at 200 Hz for 300 msec) of electrical stimuli delivered to the brain. The recording is from a DLM and reflects the abnormal HF firing of the innervating DLM motoneuron. The vertical calibration bar is 20 mV and the horizontal bar is 200 msec. (B) A low-voltage HF stimulus (8 V) fails to elicit a seizure in an eas fly carrying the esgEP2009 suppressor (genotype eas; esgEP2009/+; elav-GAL4/+) because the stimulus is below the intensity required for a higher seizure threshold. (C) A higher-voltage HF stimulus (20 V) elicits a seizure in an eas fly carrying the esgEP2009 suppressor (genotype eas; esgEP2009/+; elav-GAL4/+) because the stimulus is of sufficient intensity to exceed the higher seizure threshold of this fly. (D) HF stimuli of varying voltages were delivered to eas control flies or their siblings that were eas and carried the esgEP2009 suppressor to determine their seizure thresholds. The threshold curves show the percentage of flies that have seizures following an HF stimulus of a particular voltage. Fifteen eas control flies and 20 of their esgEP2009-carrying siblings were tested. Note that the esgEP2009 curve is broader than the control one, indicating a greater range of threshold values. (E) The esgEP suppressors raise the average seizure threshold for eas by approximately twofold. The mean seizure threshold of eas; +/CyO; elav-GAL4/+ control flies is 7.6 ± 1.9 V. The mean seizure threshold of eas flies carrying any one of the three esgEP alleles (genotype eas; esg/+; elav-GAL4/+) is higher (EP684, 15.5 ± 5.7 V; EP2009, 15.5 ± 6.8 V; and EP633, 13.3 ± 3.2 V).