[The effect on the cerebral microcirculation of in vivo stains used in biomicroscopy]

Vasoactive properties of semi-colloidal acid stains of the Evan blue and tripane blue, were revealed in rabbits and rats. The microphoto-technique revealed a dose-depending vasodilating effect of the stains. The response of the arteries had sometimes a biphasic character: constriction--dilation. I. v. administration of the stains induced a dose-dependent significant reduction of local blood flow in the cortex, subcortical white substance and other parts of the brain, of total cerebral blood flow in the venous sinus; a drop of systemic arterial pressure in normo- and hypertensive animals; a change in cerebral bioelectrical activity with increasing theta-waves, appearance of spikes and polyspikes in the EEG. Acting upon the formation of vascular tonus, these stains can interfere with the mechanisms of regulation of cerebral blood flow.