Regional cerebral blood flow changes after bilateral external carotid artery ligation in acute experimental infarction

The effect of experimental ligation of the external carotid artery and its major branches on haemorrhage from the maxillary artery

The effect of ligation of the external carotid artery and its major branches on blood flow from the maxillary artery was investigated in four Chacma baboons. The left common carotid artery and its branches were surgically exposed and the maxillary artery was isolated, sectioned and cannulated. Blood flow from the proximal segment of the maxillary artery was determined with and without occlusion of the common carotid artery, the external carotid artery above and below the origin of the linguo-facial trunk and the posterior auricular occipital trunk. Ligation of the external carotid artery below and above the origin of the lingual and facial arteries reduced maxillary artery blood flow by 40% and 73% respectively. Ligation of the external carotid artery above the origin of the lingual and facial vessels, together with ligation of the posterior auricular occipital trunk reduced maxillary artery blood flow by 99.2%. On the basis of these experimental findings, it is suggested that maxillary artery haemorrhage in man may be most effectively controlled by ligation of the external carotid artery in the retromandibular fossa, distal to the origin of the posterior auricular artery, combined with ligation of the superficial temporal artery at the root of the zygoma.

Disordered cholinergic neurotransmission and dysautoregulation after acute cerebral infarction

The possible role of displaced neurotransmitter acetylcholine (ACHh) in dysautoregulation was examined after experimental regional cerebral infarction was produced by occluding the middle cerebral artery (MCA) in babons. Regional cerebral blood flow (rCBF) was measured after intracarotid injection of 133Xenon using the gamma camera. Autoregulation was tested with metaraminol or angiotensin infusion and the autoregulation index (A.I.) was calculated. Acetylcholinesterase (ACHhE) was measured in brain tissue of noninfarcted and infarcted hemispheres. Cerebral arteriovenous (A-V) differences for cholinesterase (ChE) were also measured. Regional dysautoregulation was found in infarcted gray matter and correlated with increased AChE levels in the same zones of cortex and basal ganglia. The time course of onset of dysautoregulation correlated with increased ChE uptake by the brain. Intravenous infusion of the cholinergic neurotransmitter blocker, scopolamine, restored autoregulation to the ischemic zones. Autoregulation appears to be a myogenic reflex, influenced by neurogenic and metabolic mechanisms.