Action of Thiamine Applied Directly to the Cerebral Cortex

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Abstract
Filter paper soaked in 1, 2, 5, or 10% thiamine in normal saline was applied directly to previously located motor points of craniec-tomized dogs. After 1-2 mins. there were regular and increasingly intense rhythmic contractions of the muscles corresponding to the motor point stimulated. Afferent, repeated mechanical stimulation of the skin connected with the muscle which was in action increased the intensity and/ or the frequency of the motor reactions, which became continuous and presented the aspect of a localized convulsive reaction. Further cutaneous or simply spontaneous stimulations produced completely generalized epileptiform convulsions in 34 dogs in progressively shorter time as the concn. of thiamine was increased from 2 to 10%. Only localized muscular clonus was produced with 1% thiamine soln. and in 11 dogs only this could be obtained even when 10% solns. were used for 30 to 35 mins. With 2 and 5% solns. of cocarboxylase, the dogs showed localized muscular clonus, and 2 of 5 dogs had generalized epileptiform convulsions. The cortical application of the 2 separate thiamine moieties gave negative results. Pyridoxine hydrochloride, niacinamide, and scorbic acid similarly applied were also ineffective.