Summary1. After intracisternal administration, 6-hydroxydopamine had a greater effect on brain noradrenaline than on dopamine. 2. Administration of two doses of 6-hydroxydopamine increased the depletion of noradrenaline but not of dopamine.3. Small doses of 6-hydroxydopamine decreased the concentration of noradrenaline with little or no effect on dopamine. Tyrosine hydroxylase activity was not reduced with these treatments.4. While pargyline pretreatment offered no advantage in the depletion of brain noradrenaline after 6-hydroxydopamine, depletion of brain dopamine was greatly potentiated by this treatment. The reduction of striatal tyrosine hydroxylase activity observed after 6-hydroxydopamine was also potentiated by pargyline pretreatment. 5. The amounts of labelled noradrenaline and dopamine formed from 3H-tyrosine were greatly reduced by 6-hydroxydopamine treatment. After 3H-DOPA, formation of noradrenaline was greatly reduced while formation of labelled dopamine was only moderately reduced suggesting that decarboxylation of DOPA can occur in other than catecholamine containing neurones. 6. Desmethylimipramine and imipramine inhibited depletion of noradrenaline produced by 6-hydroxydopamine but did not alter depletion of dopamine.Reserpine did not inhibit depletion of catecholamines produced by 6-hydroxydopamine. 7. Administration of 6-hydroxydopamine to developing rats lowered both noradrenaline and dopamine concentrations as well as the tyrosine hydroxylase activity in the brains of these animals.

Ganglioside content and composition were examined in a series of 25 human gliomas, which were graded histologically by the criteria of Kernohan. The concentration of total gangliosides (lipid-bound sialic acid [LBSA]) was decreased with respect to normal brain tissue in nearly all tumors, and the extent of reduction correlated with the stage of tumor anaplasia. The distribution of individual gangliosides was altered in glial tumor tissue with an increase in proportion of the structurally simple gangliosides and reduction of polysialogangliosides. The most consistent and significant difference was the elevation of proportion of ganglioside GD3 from 4-5% of total LBSA in normal brain to 20% in the astrocytoma grade IV. The proportions of gangliosides GM2 and GD2 were also found to be elevated in all grades of the tumors. The simplification of ganglioside composition seems to be associated with transformation of the astrocyte with the accumulation of the simpler gangliosides, since the changes resemble those reported with in vitro transformation rather than those of analyses of preparations of purified glial cells.

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