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(Stroke. 2002;33:256.)
© 2002 American Heart Association, Inc.

Original Contributions

Cooling-Induced Carotid Artery Dilatation

An Experimental Study in Isolated Vessels

Seham Mustafa, PhD Olav Thulesius, MD, PhD

From the Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait.

Correspondence to Dr Seham Mustafa, Department of Pharmacology and Toxicology, Faculty of Medicine, PO Box 24923, Safat 13110, Kuwait. E-mail seham{at}hsc.kuniv.edu.kw

Background and Purpose— Clinical and experimental studies seem to indicate that hypothermia may improve outcome in stroke victims and reduce experimental brain injury. The current interpretation is that cooling has a neuroprotective effect by reducing brain metabolism. The objective of our study was to test the hypothesis that hypothermia induces arterial vasodilatation and thereby increases cerebral blood flow.

Methods— We recorded isometric tension in rabbit carotid artery strips in organ baths during stepwise cooling. The cooling responses were tested at basal tone, in noradrenaline-precontracted vessels, and after electric field stimulation.

Results— Stepwise cooling from 37°C to 4°C induced reproducible graded relaxation, inversely proportional to temperature. The responses could be elicited at basal tone and in precontracted vessels. Cooling decreased the contractile responses to norepinephrine and potassium chloride. Cooling at 20°C decreased the contractile responses to electric field stimulation, while at 10°C these were totally abolished. Cooling-induced vasodilatation is not dependent on an endothelial mechanism.

Conclusions— Cooling of carotid artery preparations induced a reversible graded vasodilatation and decreased or abolished the effect of vasocontractile neurotransmitters. The effect of local hypothermia could increase cerebral blood flow and may constitute a positive therapeutic modality in stroke patients.

Key Words: carotid arteries • hypothermia • ischemia • neuroprotection • stroke

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