Cooling-induced carotid artery dilatation: an experimental study in isolated vessels.
OBJECTIVE
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 degrees C to 4 degrees 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 degrees C decreased the contractile responses to electric field stimulation, while at 10 degrees 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.
Mustafa
Seham
S
Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait. seham@hsc.kuniv.edu.kw
Thulesius
Olav
O
D000818:Animals; D002339:Carotid Arteries / Q000187:drug effects / Q000502:physiology*; D002540:Cerebral Cortex / Q000098:blood supply; D003080:Cold Temperature; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D007036:Hypothermia, Induced; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D012039:Regional Blood Flow; D020521:Stroke / Q000628:therapy; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation
D014662:Vasoconstrictor Agents; D011189:Potassium Chloride; D009638:Norepinephrine