The effect of increased nitrogen pressure on motor activity and the intercentral relationships of the brain of monkeys.

The influence of increased nitrogen pressure up to 19 ata was investigated in chronic experiments on monkeys of a species of Javan macaques (Macaca irus) with electrodes implanted in cortical and subcortical regions of the brain. The phasic character of the changes of motor activity of the animals, an increase in the spectral density of the average power of the EEG in the range of frequencies from 4 to 20 Hz, and a disturbance in the connectedness of the electrogenesis of the reticular formation of the midbrain with the bioelectrical processes in the substantia nigra, the head of the caudate nucleus, and the frontal and motoric areas of the cortex were identified in the course of nitrogen compression at a rate of 1.0 ata per 1 min.

[Central action of a new cholinesterase reactivator, diethyxime].

In anesthetized cats, whose peripheral muscarinic-cholinorecptors are blocked by m-cholinolytics (benzilyl choline) failing to penetrate into the brain, the cholinesterases reactivator diethyxime debars the centrally caused fall of the arterial pressure produced by armine, an inhibitor of cholinesterases readily gaining access into the brain. Diethyxime is also capable of abolishing the depression of the phrenic nerve action potentials produced by armine. Dipyroxime-a quaternary diethyxime analogue and also a quaternary cholinesterase reactivator fails to produce such an effect.

[Muscarin-sensitive cholinoreactive systems in the respiratory center].

Muscarinic cholinergic drugs (arecoline, oxotremorine) which can easily overcome the blood-brain barrier inhibit the action potentials of the phrenic nerve in anesthetized or decerebrate curarized cats after a selective blockade of peripheral muscarinic cholinoreceptors with quaternary anticholinergic drugs (oxyphenonium, benzilycholine). These inhibitory effects are abolished by drugs blocking the central muscarinic cholinoreceptors (atropine, scopolamine, benactyzine). This suggests the existence of muscarinic cholinoreceptive neurons in the respiratory center of the cerebral ponto-bulbar region, the said neurons inhibiting the activity of the inspiratory motonerons.