para^GEFS+ adults undergo seizure-like activity in response to increased temperature

para^GEFS+ heterozygous and homozygous adults exhibit a frequent and fully penetrant, respectively, heat-induced (40[o]C of temperature) seizure phenotype within 2min of exposure.

para^GEFS+/para^GEFS+ flies (virgin or mated females, or hemizygous males) have significantly increased daytime activity and decreased nighttime activity compared to controls; activity drops sharply upon lights off. Total daytime sleep is marginally affected (slight decreases in virgin females, and males, slight increase in mated females), whereas nighttime sleep is dramatically increased.

Nighttime sleep is significantly affected in para^GEFS+/para^GEFS+ or para^GEFS+/+ mated females: increased percentage time asleep, decreased sleep latency, increased sleep bout duration, decreased wake bout duration, increased waking activity (despite less awake time); sleep bout number is also significantly decreased in heterozygotes. Nighttime sleep analysis of mated para^GEFS+/para^GEFS+ females based on video recordings (rather than DAMs) also finds significant increases in total sleep time, bout number and bout length, along with significant decreases in sleep latency and wake bout length and waking activity. Heterozygous para^GEFS+/ mated females outcrossed once to wild-type strains show less severe phenotypes, but still display significant increases in nighttime sleep and reduced sleep latency compared to controls. para^GEFS+/para^GEFS+ virgin female lifespan is comparable to controls.

As expected, feeding mated female flies carbamazepine (CBZ) reduces nighttime sleep and increases sleep latency in a dose-dependent manner; however the lowest concentration (0.1mg/ml) only has significant effects in control but not para^GEFS+/para^GEFS+ flies, and mutants show significantly less percent change in nighttime sleep compared to controls at all CBZ concentrations.

Under constant light (LL) conditions, para^GEFS+/para^GEFS+ mated females still sleep significantly more than controls, but the short sleep latency phenotype seen in LD conditions in mutants compared to controls is eliminated. Both controls and mutants suppress sleep in response to a nocturnal light interruption (1hr of light 5hrs after lights off), though mutants are significantly more active during the light stimulus; sleep latency in mutants remains significantly shorter than controls after the end of the nocturnal light interruption. para^GEFS+/para^GEFS+ mutants have normal circadian rhythms and tau unchanged under constant dark conditions.

Unlike control flies after 24hr mechanical sleep deprivation, para^GEFS+/para^GEFS+ or para^GEFS+/+ mated females do not show significantly reduced sleep latency and increased time asleep (rebound). A small but significant percentage of control flies show heat-induced (2min exposure to 40[o]C) seizure-like behavior after sleep deprivation (compared to none showing seizure behavior without sleep deprivation), whereas sleep deprived para^GEFS+/para^GEFS+ flies are less likely than untreated counterparts to have heat-induced seizures.

At room temperature, para^GEFS+ flies exhibit abnormal behaviors that appear to mimic partial seizures, such as repetitive grooming that often results in broken wings in aged flies. Some para^DS.S1231R flies display rapid wing flapping while walking, causing the flies to lose balance and bounce around in the vials. However, at the normal rearing temperature (22-24[o]C), the spontaneous seizure-like events occur at low frequency and are variable in nature and duration.

The heat-induced seizures found in para^GEFS+ flies are exacerbated in a 5-HTP dose-dependent manner.

Hemizygous males and homozygous females show a heat-induced seizure phenotype. When transferred to 40[o]C, both sexes show an initial period of increased locomotor velocity followed by seizure activity. The probability of seizing increases as a function of time and by 2 minutes at 40[o]C, more than 96% of flies are seizing. Males and females show the same phenotype. When flies are transferred back to room temperature, there is an abrupt cessation of activity. The flies remain motionless and are unresponsive to tapping of the vial for varying periods of time before showing brief periods of spontaneous movement, generally in one or two legs. Recovery of the ability to stand and resume walking or climbing behaviour requires 9-28 minutes.

Heterozygous females also show a heat-induced seizure phenotype upon exposure to 40[o]C for 2 minutes, although the time to seizure onset is delayed and the maximal probability of seizing is less than in homozygotes. 21% of heterozygous females show no seizures. The remaining 79% show seizure activity, but this can start and stop more than once during the 2 minute period at 40[o]C. Recovery of the ability to stand and resume normal locomotion after transfer back to room temperature requires 7-20 minutes.

GABAergic local neurons (LNs) in the dorsal lateral aspect of the antennal lobe of para^GEFS+ flies show alterations in sodium currents compared to controls at elevated temperature. The mutant LNs show prolonged poststimulus depolarization and reduced firing frequency at 35[o]C.