Characterization of naturally occurring materials which restore excitability to isolated cerebral tissues

Abstract

Cerebral tissues kept in cold media do not give their normal respiratory response to pulses when subsequently brought to 37[degree]. Response was restored by including certain fractions of blood plasma proteins in the media during incubation. The potency of different plasma fractions in restoring response was correlated with their content of neuraminic acid derivatives. Other substances of large molecular weight and containing neuraminic acid also restored the tissue''s response: a sialomucopolysac-charide and preparations of gangliosides from the brain which were active at a concentration of 150 [mu]g/ml of medium. An analogous unresponsive state was induced in normal cerebral tissues by incubation with protamines, histones or a synthetic poly-L-lysine at a concentration of 30-150 [mu]g/ml. Response here also, after inhibition by protamine, was restored by gangliosides. Prior mixture of an amount of protamine normally inhibitory, with a little more than its own weight of gangliosides, prevented the protamine from exerting its inhibition. Concentrations of gangliosides which restored response to the tissue kept cold or with protamine, when added to protamine without tissue, prevented the protamine being precipitated by picric acid or fluorescein. This was attributed to complex formation between gangliosides and protamine; similar phenomena were shown with inhibitory concentrations of histone, and also between the sialomucopolysaccharide and the basic proteins. The quantities of the basic proteins and gangliosides which interact in conditioning the response of a tissue specimen are compatible with the proteins inhibiting the combination with the gangliosides of the specimen. The possibility is discussed of such a mechanism operating when response is lost on keeping the tissue in cold media or with protamine.