Mapping of cerebral blood flow changes during audiogenic seizures in Wistar rats: effect of kindling

The quantitative autoradiographic [14C]iodoantipyrine technique was applied to the measurement of rates of local cerebral blood flow (LCBF) during audiogenic seizures in Wistar AS rats belonging to a genetic strain selected at the Centre de Neurochimie (Strasbourg, France) for their sensitivity to sound. Seizures were elicited in native rats never exposed to sound (single audiogenic seizures) or in rats previously exposed to 10-40 seizure-inducing sound stimulations until generalization of the seizure to forebrain areas (referred to as "kindled animals"). During single audiogenic seizures, rates of LCBF increased over control values in all areas but the genu of the corpus callosum. The highest increases in LCBF (180-388%) were recorded in the inferior and superior colliculus, reticular formation, monoaminergic cell groupings, especially the substantia nigra, posterior vegetative nuclei, and many thalamic and hypothalamic regions. The lowest increases were seen in forebrain limbic regions and cortical areas. In kindled animals, LCBF rates increased over control levels in 67 areas of the 75 studied. LCBF increases were generally of a lower amplitude in kindled than in naive rats. Differences between the two groups of seizing rats were located mostly in brain-stem regions, mainly the inferior colliculus, reticular formation, substantia nigra, and posterior vegetative nuclei. Conversely, rates of LCBF were similar in forebrain areas of naive and kindled animals. In conclusion, the present data show that there is a good correlation between the structures known to be involved in the expression of audiogenic seizures (inferior colliculus, reticular formation, substantia nigra mainly) and the large increase in LCBF during single audiogenic seizures, while rates of LCBF increase to a lesser extent in forebrain areas not involved in this type of seizures. The circulatory adaptation to kindled seizures is rather a decreased response in brain-stem regions and no change in the forebrain, although the kindling process induces a generalization of the seizure from brain-stem to anterior regions.