Convulsant Stimuli Research Articles

Regional distribution of arachidonic acid metabolites in rat brain following convulsive stimuli

Seizures were induced in female Wistar rats by electroconvulsive shock (ECS) or administration of pentetrazole (PTZ). Brain content of various prostanoids measured by radioimmunoassay showed time-dependent changes after the induction of convulsions; highest levels were found for PGD 2 followed by PGF 2α, PGE 2, TXB 2 and 6-keto-PGF 1α. Analysis of the various arachidonic acid metabolites in seven parts of the rat brain dissected according to the method of Glowinski and Iversen revealed the largest increases in hippocampus and cerebral cortex and smaller ones also in hypothalamus and corpus striatum both after ECS and PTZ. The ratios of the different cyclo-oxygenase products remained virtually the same in whole brain as well as in those regions where the formation of prostaglandins was markedly elevated. 15-keto-13,14-dihydro-PGF 2α also increased simultaneously in parallel to its parent compound, PGF 2α and was detected in significant amounts only in hippocampus and cerebral cortex. However, concentrations of 15-keto-13,14-dihydro-PGF 2α in these brain regions as well as in whole brain represented only 3–10% of the amounts found for PGF 2α. Thus, the metabolizing enzymes 15-hydroxy-PG-dehydrogenase and Δ13-PG-reductase seem to be of minor importance for the inactivation of prostanoids in brain tissue.

Effect of Naja naja venom and a heparin-precipitable portion on threshold to nocioceptive and convulsive stimuli on rats : M. Dzoljic and I. L. Bonta. (Department of Pharmacology, Medical Faculty Rotterdam, Rotterdam, The Netherlands)

Effect of Naja naja venom and a heparin-precipitable portion on threshold to nocioceptive and convulsive stimuli on rats : M. Dzoljic and I. L. Bonta. (Department of Pharmacology, Medical Faculty Rotterdam, Rotterdam, The Netherlands)

Acetylcholine and the epileptiform activity of chronically isolated cortex. I. Macroelectrode studies.

Solutions of acetylcholine were applied to the chronically isolated and the contralateral occipital cortex of cats prepared as encephale isole. The amounts required to produce epileptiform discharges were similar on the two sides. The spontaneous paroxysmal activity in the island was not facilitated by the application of acetylcholine but it disappeared before or at the onset of acetylcholine-induced discharges. Electrical stimulation revealed neither a decrease of the threshold for epileptiform afterdischarges nor a facilitation of spontaneous discharges on the isolated side. However, the seizure discharges in the isolated area, once induced by either acetylcholine or electrical stimulation, continued for long periods of time. The results suggest that acetylcholine acts as a convulsant stimulus without a special relationship to the intrinsic epileptiform abnormality of the isolated cortex.

Evaluation of five methods for testing anticonvulsant activities.

Summary1. Anticonvulsant activities of 10 CNS depressants were determined by the following 5 procedures: (a) Supramaximal electroshock; (b) supramaximal chemoshock (Metrazol); (c) “psychomotor” seizure; (d) subcutaneous Metrazol; and (e) intravenous Metrazol (a minimal convulsive dose). 2. Results indicate that intensity of convulsive stimuli, electrical or Metrazol, is the important factor in determining anticonvulsant property of a compound. The order of anticonvulsant activities of these compounds is the same whether determined according to the first two methods by the abolition of hind leg extensor seizure, or according to the latter three methods by the inhibition of a minimal clonic seizure response. 3. Reasons are given for our preference of the supramaximal electroshock and the subcutaneous Metrazol method for screening for potential antiepileptic compounds.