Polybasic and polyacidic substances or aggregates and the excitability of cerebral tissues, electrically stimulated in vitro

Abstract

Cerebral-cortical tissues lost their normal excitability on incubation in protamine-containing media, rinsing and examination in a second medium similar to the first but without protamine. Excitability could be restored by adding ganglioside preparations to the second medium; this property of the gangliosides was lost on mild acid-treatment which removed their N-acetylneuraminic acid residue. Phosphatidylserine and sulphatide preparations also restored excitability, though for a given effect they were required in greater concentrations than were the gangliosides. Their restoring activity was attributed to the polyacidic aggregates existing in their aqueous solutions; phos-phatidylethanolamine and lecithin showed lesser activity. Chondroitin sulphates, suramin and polyglutamic acids (descending order of activity) also restored excitability. The effective agents complied with the following general description: they were polyacidic or existed in aqueous solution as polyacidic aggregates, and were required in quantities equivalent to or greater than the basic groups added to the tissue by the protamine with which it had been incubated.