Absent or Not?: Classically Conditioning Spike-and-Wave Discharge in Sprague Dawley Rats

Spike-and-wave discharge is an electroencephalographic brainwave found in many rodent species and studied rigorously in inbred laboratory rats (WAG/Rij and GAERS strains) for its similarities to absence epilepsy. The absence epilepsy research field, however, is divided on just how similar SWD in rats is to absence epilepsy in humans. Albino Sprague Dawley rats are an outbred strain used in many fields of research but presently are not used to study absence epilepsy despite being known to exhibit SWD. Five 10 month old male albino Sprague Dawley rats that presented with SWD were rewarded with a 45 mg sugar pellet three seconds after an SWD burst ended. An infrared photo-beam diode was used to track reward tray checking behavior in relation to reward dispensation. It was found that pairing a sugar reward with SWD resulted in a reduced average SWD duration (<1/2 of baseline) and that the rats would preemptively check the reward tray for sugar after completing a burst of SWD. Rats were then given ethosuximide, a known anti-epileptic drug, to confirm that SWD was suppressed by ethosuximide as it is in other SWD rodent models of absence epilepsy. SWD was found to be suppressed in the five Sprague Dawley rats when given ethosuximide. Together, these results suggest that Sprague Dawley rats are conscious during and have voluntary control of SWD and therefore are not experiencing absence seizures. Furthermore, the findings imply that SWD rodent models of absence epilepsy may be mistakenly studying a non-absence epilepsy phenomena.