Local cerebral glucose utilization in adult and immature GAERS

In the present study, we compared the basal local cerebral metabolic rates for glucose (LCMRglcs) both in Wistar rats with genetic absence epilepsy (GAERS: genetic absence epilepsy rats from Strasbourg) and in control non epileptic (NE) rats selected in our breeding colony. LCMRglc was measured both in immature rats at postnatal day 21 (P21) at which age no spontaneous spike-and-wave discharges can be recorded in GAERS and at the adult age (6 months) when GAERS fully express thalamo-cortical spike-and-wave discharges recorded on the EEG. LCMRglcs were measured in 24 structures by the quantitative [14C]2-deoxyglucose autoradiographic technique. In adults GAERS, LCMRglc underwent a widespread increase recorded in all brain structures except in mediodorsal and ventromedian thalamus, and in the nucleus accumbens. These metabolic increases ranged from 17 to 50% over control levels in adult NE rats. In P21 GAERS, LCMRglc was similar to that of P21 NE rats in 16 areas. It increased over control levels of NE rats in two groups of structures. Metabolic increases were recorded in four limbic structures (entorhinal and piriform cortices, hippocampus and basolateral amygdala) where no spike-and-wave discharges were recorded in adult GAERS. Increases in LCMRglcs were also located in the substantia nigra pars reticulata, superior colliculus and globus pallidus which are structures involved in the control of seizure activity. In conclusion, our data suggest that the consequences of the genetic mutation(s) underlying the cellular and molecular events responsible for the expression of spike-and-wave discharges in adult GAERS is (are) able to increase metabolic activity in both limbic structures and the nigral inhibitory system before the occurrence of spike-and-wave discharges.