Application of electrocapacitography to investigation of cephalic and cerebral circulation in the rabbit

Electrocapacitography devised for medical purposes by Hatakeyama was applied as a noninvasive volumetric method to investigate circulation in the rabbit head and brain. The effective electric capacitance was measured by means of a highly sensitive device. An electrocapacitogram (ECPG) of the head, considered to reflect the volume of intracranial as well as extracranial blood vessels, varied rhythmically with cardiac beat and respiratory movement. In general, the pulsatile variations of ECPG in synchronization with cardiac beat (ECPG pulse) bore a resemblance to arterial pulse. Occlusion of the common carotid artery caused the ECPG level corresponding to mean vascular volume to fall markedly and in most cases the amplitude of ECPG pulse was diminished. By rapid infusion of 5 ml of the blood into intracranial blood vessels via the internal carotid artery or into extracranial blood vessels via the external carotid artery, ECPG level was raised transitorily, the effect of extracranial infusion being larger than that of intracranial infusion. Stimulation of the central cut end of the cervical sympathetic nerve reduced ECPG level considerably. This response was greatly diminished by carotid occlusion and sometimes a temporary rise of ECPG was observed at the beginning of the stimulation. In several cases the effect was reversed completely by carotid occlusion and an increase of ECPG during the stimulation was observed. These findings suggest the existence of a sympathetic vasoconstrictor in the head as well as a sympathetic vasodilator of the brain, although in confirmation of this review further investigation is required. ECPG of the head is demonstrated to be a useful method for investigating circulation in the head including brain.