Physiological and drug-induced changes in the glycogen content of mouse brain

An ultrastructural study of methionine sulphoximine-induced glycogen accumulation in astrocytes of the mouse cerebral cortex

Glycogen distribution in the mouse cerebral cortex was examined with electron microscopy following treatment with the experimental convulsant, methionine sulphoximine (M.S.O.). Both at 24 and 48 h followed administration of M.S.O., accumulation of particulate glycogen was prominent in astrocytes throughout the cerebral cortex. In astrocyte cell bodies and in subpial, pericapillary and perineuronal astrocyte processes the glycogen often completely filled the cytoplasm, crowding the remaining organelles and inclusions. The present findings correlate well with biochemical studies of M.S.O. effects of glutamine synthetase activity and energy metabolism. It is suggested that the glycogen may be derived from glutamate which under normal conditions would be converted to glutamine.

Effect of depletion of cerebral monoamines on the concentration of glycogen and on amphetamine-induced glycogenolysis in the brain

1. An increase in the concentration of glycogen occurs in the mouse brain after depletion of cerebral catecholamines by alpha methyl-p-tyrosine methylester (H44/68), diethyldithiocarbamate, or reserpine.2. Depletion of cerebral 5-hydroxytryptamine with parachlorophenylalanine (PCPA) does not result in a change in the concentration of brain glycogen.3. When H44/68 is administered together with reserpine to inhibit the synthesis and storage of cerebral catecholamines, and thus bring about their total depletion from the brain, the cerebral glycogenolytic effect of amphetamine is abolished.4. Amphetamine-inducing glycogenolysis is only partially antagonized if only one of the catecholamine-depleting agents H44/68, diethyldithiocarbamate, or reserpine is injected prior to the amphetamine. The persistence of this glycogenolytic effect of amphetamine is possibly due to the presence of residual stores of catecholamines available for release by the stimulant drug.5. Depletion of cerebral 5-hydroxytryptamine by PCPA does not result in any antagonism of amphetamine-induced glycogenolysis.6. The results suggest that amphetamine depletes brain glycogen by the release of central catecholamines rather than by a direct action at receptors.

Effect of receptor blocking drugs on the depletion of brain glycogen by amphetamine

1. Amphetamine sulphate (5 mg/kg), administered intraperitoneally, reduces the concentration of glycogen in the mouse brain by 25-30% after 30 minutes.2. The effect of several receptor blocking drugs on the amphetamine-induced cerebral glycogenolysis was studied.3. DL-Propranolol (0.25 mg/kg) and pronethalol (10 mg/kg) antagonized the depletion of brain glycogen by amphetamine.4. Phentolamine, methysergide, atropine and mepyramine failed to antagonize the amphetamine-induced glycogenolysis.5. D-Propranolol, chlorpromazine and phenoxybenzamine antagonized the glycogenolytic effect of amphetamine only when administered in sedative doses.6. It is concluded that amphetamine-induced glycogenolysis in the mouse brain may be mediated through a beta-adrenoceptor.

Cyclic adenosine monophosphate in brain areas: microwave irradiation as a means of tissue fixation

Amounts of cyclic adenosine monophosphate in discrete regions of the brain were estimated after exposure of rats to microwave irradiation. Amounts were highest in the cerebellum and brainstem, intermediate in the hypothalamus and midbrain, and lowest in the hippocampus and cortex. Decapitation increased the concentration of cyclic adenosine monophosphate in all brain areas, although the increase in the cerebellum was three to four times greater than that in other areas. Microwave irradiation may provide a means of rapidly fixing brain tissue in situ while permitting easy dissection of the brain. In this way artifacts produced by decapitation can be eliminated, and concentrations of heat-stable compounds in the brain can be estimated under conditions which more closely approximate those in vivo.