After several trains of intermittent photic stimulation (IPS) each lasting 10 seconds and sometimes inducing paroxysmal electrical activity, isolated flashes or salves of 2 or 3 light flashes are capable of inducing bifrontal paroxysmal discharges in photosensitive Papio papio, an effect which is augmented by allylglycine or the use of highly photosensitive animals. Use of these salves repeated every second enabled the authors to demonstrate two types of changes in cortical excitability after intermittent photic stimulation: 1. responses which were more frequent and of greater amplitude appearing in the first 3 or 4 seconds after IPS; after paralysis of the animal amplitude and frequency of the responses are augmented. 2. if trains of intermittent photic stimulation are repeated regularly a seizure occurs after 5 to 15 trains. In the paralysed animal, more trains are required although large responses are seen after each train whereas in the non-paralysed animal the seizure occurs rapidly but the responses are on average weaker and less frequent than in 1. The relationship between photosensitive epilepsy and these responses is discussed as well as that of somatic afferents.

Animals↗

PubMedDate not supplied

[The induction of seizures in "Papio papio" following allylglycine alone or in combination with intermittent photic stimulation (author's transl)].

Allylglycine, an inhibitor of GABA synthesis, produces increased sensitivity to photic stimulation and in convulsant doses spontaneous seizures arising occipitally in the baboon (Horton and Meldrum, 1973). In this study, convulsant doses of allylglycine induced either sharp wave and polyspike frontorolandic discharges (FR) or critical posterior discharges which then reinforce the fronto-rolandic spikes. A seizure may then arise from the fronto-rolandic region and secondarily spread to the rest of the cerebral cortex. Intermittent photic stimulation produces a reinforcement of the fronto-rolandic sharp waves and can also induce self-maintaining mechanisms similar to those just described. In this situation, however, and with the animals paralysed with Flaxedil no seizures arising occipitally have been observed. The role of the occipital cortex as the sensory visual and somatic afferent in photosensitive epilepsy in the baboon is discussed in the light of these results.

Allyl Compounds↗

PubMedDate not supplied

[Approach to self medication in rheumatology. Apropos of the study of a series of 895 patients who have come for consultation in rheumatology].

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Adult↗