Gangliosides and related substances of isolated cerebral tissues examined in relation to tissue excitability

Abstract

N-Acylneuraminic acid derivatives have been determined by the orcinol-ferric chloride reaction in cerebral tissues, after extraction and solvent partition by methods which yield ganglioside preparations. The resulting values for ganglioside-like substances are expressed by reference to synthetic N-acetylneuraminic acid. Tissues frozen in situ gave values of 1.8 [mu]mole/g., close to those of tissue dissected at room temperature. Incubation in oxygenated glucose media had little effect on these values, but diminution to 1.3-1.5 [mu]mole/g was found after incubating with protamine or after keeping in cold media before incubation. These are conditions under which the tissue''s metabolic response to electrical pulses is lost. Further quantities of ganglioside -like substances could be extracted from tissues in the presence of suramin. A number of other substances were inactive in this respect; suramin increases response by the tissue. Suramin also increased the yield of ganglioside-like substances when these were estimated by an independent method which depended on hydrolysis and reaction with periodate, followed by thiobarbituric acid. The total ganglioside-like substances, which included those extracted in the presence of suramin, also diminished under the conditions of paragraph 2 above. Subsequent incubation with gangliosides under conditions allowing restoration of response to pulses, increased the ganglioside extractable from the tissue. Incubation with gangliosides did not have a comparable effect on normal tissue. The findings indicate heterogeneity in the tissue gangliosides and the association of at least one component with the tissue''s ability to respond to pulses.