Role of cholinergic mechanisms in alterations of rabbit brain functional activity during sea-sickness

Using the hydrogen-clearance method in chronic experiments on alert rabbits, we investigated the dynamics of changes in local and total cerebral blood-flow, oxygen pressure, bioelectrical activity of the motor, auditory, and visual zones of the cerebral cortex, the heart rate during sea-sickness and the effect of the cholinolytic scopolamine upon changes in these indices. It was found that scopolamine affects the character and direction of changes in both local and overall blood flow in the brain during sea-sickness. Scopolamine does not substantially alter oxygen pressure in the cortical structure of the brain and does not eliminate brachycardia arising during sea-sickness. On the electrocorticogram (ECoG), it does cause an intensification of activational processes and an increase in the total bioelectrical activity, especially in the motor zones of the cerebral cortex. It is suggested that the protective effect of scopolamine during sea-sickness is connected with its central cholinolytic action and with the decrease it brings about in the cerebral hemodynamics and bioelectrical activity of the cerebral cortex arising during "motion sickness."