Influence of various stimuli on lactic acid, alanine and gamma-aminobutyric acid levels in rat brains.

Abstract

As has previously been shown1,2, an increase of lactic acid, alanine and γ-aminobutyric acid in the brain of rats occurred when, after tying both carotids, stimuli were applied to the cortex which caused electroencephalographic depression. This communication is concerned with the way in which the aforementioned metabolites are influenced after stimuli causing depression (3 and 0.3 M solutions of potassium chloride, rubidium chloride, caesium chloride and ammonium chloride), after stimuli not causing depression (3 and 0.3 M solutions of lithium chloride and sodium chloride), after stimuli blocking the spreading of the depression (3 and 0.3 M solutions of magnesium chloride and calcium chloride3) and after stimuli causing the increased activity of the nervous system (1 and 10 per cent solutions of pentamethylen-tetrazol and 0.1 and 1 per cent solutions of strychnine), when both carotids were tied. All stimuli were applied on the exposed cortex by placing a piece of filter paper dipped in the used solution on the cortex for 30 min. The brains were then fixed in liquid air. In ethanol extracts of the frozen brains the free amino-acids were determined by paper chromatography according to the method of Rindi and Ferrari4 and in trichloroacetic acid extracts lactic acid was estimated according to the method of Barker and Summerson5. All results are expressed as μmoles of the compound investigated per gram of protein nitrogen, which was determined by the micro-Kjeldahl distillation method. For statistical evaluation Student's t test, unpaired variates, was used.