AN EXPERIMENTAL-MODEL OF GENERALIZED SEIZURES FOR THE MEASUREMENT OF LOCAL CEREBRAL GLUCOSE-UTILIZATION IN THE IMMATURE RAT .1. BEHAVIORAL CHARACTERIZATION AND DETERMINATION OF LUMPED CONSTANT

An experimental model of status epilepticus has been developed in the immature rat by administration of pentylenetetrazol (PTZ) using repetitive, timed intraperitoneal injections of subconvulsive doses. The pattern of behavioral signs has been well characterized in each age group, i.e. 10 (P10), 14 (P14), 17 (P17) and 21 postnatal days (P21). In this model, the dose of convulsant could be adjusted as a function of interindividual sensitivity, and status epilepticus lasted for quite a long duration to allow the measurement of local cerebral metabolic rates for glucose (LCMRglc) by means of the [C-14]2-deoxyglucose method [J. Neurochem, 28 (1977) 897-916]. To estimate LCMRglc during status epilepticus, the lumped constant (LC) was re-calculated in controls and PTZ-treated rats. The control LC was 0.54 at P10 and 0.50-0.51 at the three older ages studied (P14, P17 and P21). During status epilepticus, it increased to 0.64 in P10 rats.and decreased to 0.42 and 0.40, respectively, in P17 and P21 animals. At P14, LC was not affected by seizures. The measurements of brain lactate levels showed a large 4.5-10-fold increase in PTZ-treated rats as compared to controls at all ages. The results of the present study show that the immature brain responds to sustained seizure activity in a specific way according to its postnatal age. Moreover, our results underscore the necessity bf re-calculation of LC to the quantification of LCMRglc in such pathological states, particularly in immature animals.