A Method for Study of the Interrelation Between EEG and Blood‐Brain Barrier phenomena

Abstract

An experimental procedure has been elaborated to facilitate selective effects exerted by agents applied within the cerebral vessels on EEG and blood‐brain barrier phenomena. In rabbits short‐term (less than 1 minute) perfusion of one hemisphere is performed via the ipsilateral internal carotid artery with a pressure adjusted so as to obtain displacement of the blood. This displacement is controlled by inspection of the pial vessels through a trephine opening. The technique implies control of the active concentration in loco of the applied agents and of the application time, hence graded influences near the threshold levels can be obtained. Structural and metabolic considerations make it conceivable that low grade damage of the blood‐brain barrier may be produced with no significant effect on the neuronal activity as reflected in EEG (except for the brief influence from the blood deprivation). After such damage intravenous administration of suitable substances, unable to pass the intact barrier, may give rise to unilateral EEG changes and thus reveal the defective barrier function. Two model experiments are reported. The first one shows that unilateral blood deprivation per se (for about 2 min) exerts a marked but reversible effect on the EEG without damage to the blood‐brain barrier as tested by intravenously injected trypan blue. The second experiment illustrates an attempt to induce barrier damage without significant changes in the EEG.

Increased growth hormone response to dopamine infusion in insulin-dependent diabetic subjects: indication of possible blood-brain barrier abnormality.

“…A negative answer must be qualified by the fact that early and even late stages of diabetic retinopathy are often totally asymptomatic and remain undetected until fluorescein angiography is performed or major events take place, such as a vitreous hemorrhage, macular involvement, or retinal detachment. In experimental disruption of the blood-brain barrier, no changes in EEG are detectable until the damaged system is challenged with acute administration of suitable substances (48).…”

Differentiated Effects on Certain Blood‐Brain Barrier Phenomena and on the EEG Produced by Means of Intracarotidally Applied Mercuric Dichloride

“…The asymmetrical EEG pattern in stage I, appearing during the carotid injection, can for the most part be attributed to the anoxia a t the blood expulsion as previously discussed (FLODMARK and STEINWALL 1962). The tendenc)…”

Vasopressor Potentiation of Neurotoxicity in Experimental Aortography

“…In any event, a violent convulsive reaction does not always presage a necrotizing effect, nor does the lack of this discharge predicate the absence of toxic anatomic sequelae. Although changes in the blood brain barrier produced by contrast media have been demonstrated to be reversible (7,9,14,15,58,59), correlative pathologic studies must be done to exclude the absence of irreversible anatomic effects in such experiments. In any event, at our present state of knowledge, the use of contrast agents for the purpose of increasing the passage of therapeutic drugs into the brain is not justified.…”