Regional cerebral blood flow in the rat during prolonged seizure activity

In order to evaluate the possible contribution of regional insufficiency in blood flow to the development of epileptic brain damage, we have measured changes in total and regional cerebral blood flow (tCBF and rCBF) during the course of prolonged sustained seizures. We have used both a particle distribution method (radioactively labelled microspheres) and a diffusible tracer method (iodo [14C]antipyrine). Seizures were induced with bicuculline (1.2 mg/kg, i.v.) in rats with neuromuscular paralysis, mechanically ventilated with 70% N2O/30% O2, rCBF was determined in 13 brain regions after 10, 30, 60 and 120 min of seizure activity. Microsphere and iodo[14C]antipyrine methods gave identical control values for tCBF (0.88 +/- 0.02 vs 0.86 +/- 0.07 ml/g brain/min) and closely similar rCBF values. The increases in tCBF after 10 and 30 min seizure activity were less as measured with microspheres than with iodo [14C]antipyrine (2.42 +/- 0.29 vs. 4.99 +/- 0.94 and 1.79 +/- 0.18 vs 3.05 +/- 0.30 mg/g brain/min, respectively). With microspheres, rCBF values showed considerable interhemisphere variability, but did not do so with iodo [14C]antipyrine. The regional pattern of flow changed during seizures. Changes in neocortical rCBF tended to match changes in tCBF. Consistent decreases in rCBF relative to tCBF were seen in the pons-medulla and cerebellum at all seizures times. Relative increases in rCBF were seen at all seizure times in the thalamus, and at 10 and 30 min in colliculi and midbrain. In the hippocampus, rCBF was unchanged (relative to tCBF) at 10 and 30 min, but was increased at 60 and 120 min of seizure activity. Thus, regions developing epileptic brain damage in this model of status epilepticus (hippocampus, thalamus, neocortex) show increases in rCBF greater than those in regions not showing brain damage (cerebellum, brain stem).