Neurotropic drugs, electroshock and carbohydrate metabolism in the rat

Centrally mediated drug-induced hyperglycemia in mice

In mice, the hyperglycemic response to a stress, such as repeated orbital puncture, evoked a hyperglycemia through activation of the adrenal medulla and consequent release of catecholamines. This hyperglycemia could be blocked by pretreatment of the mice with the ganglionic blocking agent, chlorisondamine. The hyperglycemic response evoked by single doses of serotonin receptor blocking agents, such as cyproheptadine and methysergide, or by dopamine receptor blockings drugs, such as haloperidol or chlorpromazine, could also be blocked by pretreatment with chlorisondamine. Administration of a single dose of the muscarinic agonist, oxotremorine, also resulted in a hyperglycemia that was blocked by chlorisondamine. The results are compatible with the hypothesis that the adrenal medulla is under the control of a central cholinergic pathway with dopaminergic and serotonergic modulating systems.

Plasma corticosterone responses to stress following chronic oral administration of diazepam in the rat

The effect of daily, oral administration of diazepam on plasma corticosterone responses to stressors of varying intensity was investigated. In rats exposed to the mild stress of noise, diazepam, 10 mg kg-1 but not 1.0 or 0.1 mg kg-1, reduced plasma corticosterone concentrations by 30% in comparison with controls. However, in rats exposed to the more severe stressors, foot-shock or immobilization, none of these doses of diazepam reduced plasma corticosterone responses. In unstressed rats, diazepam 10 mg kg-1 raised plasma corticosterone concentrations. It is suggested that plasma corticosterone concentrations are not a reliable indicator of the tranquillizing effect of diazepam during stress.

The comparative effects of barbituric acid phenobarbital on blood glucose and insulin secretion in mice

The effects of barbituric acid and phenobarbital upon carbohydrate metabolism in mice were compared. An intraperitoneal dose of 100 mg/kg of barbituric acid increased blood glucose concentrations during an intravenous glucose tolerance test, but did not alter the rate of glucose disappearance from the blood. Barbituric acid also antagonized the hypoglycemic effect of intravenously administered tolbutamide. The same dose of phenobarbital had no effect. An in vitro concentration of 100 mug/ml of barbituric acid decreased the responsiveness of isolated mouse pancreatic islets to glucose stimulation (3.0 mg/ml D-glucose). Again phenobarbital, 100 mug/ml, was without effect. The structural similarities between barbituric acid, tolbutamide and alloxan suggest that the effects observed in these experiments might reflect a competition for binding to reactive sites on or within the pancreatic B-cell.