Cerebral infarction due to carotid occlusion and carbon monoxide exposure. II. Influence of preganglionic cervical sympathectomy.

Abstract

SUMMARY Unilateral cerebral infarcts were produced in the rat by ligation of one common carotid artery and subsequent exposure to carbon monoxide. The incidence and extension of brain infarcts was increased in animals with additional ipsilateral cervical preganglionic sympathectomy. Sympathectomy did not affect markedly the respiration and systemic circulation. The effect of sympathectomy was attributed to a cutaneous vasodilation, leading to an extracranial steal phenomenon.The role of the cervical sympathetic innervation of the cerebral vessels is controversal. It is generally accepted that the influence of the sympathetic innervation on the extracranial vasculature is much more effective than on the intracranial bed. Since the extra-and intracranial vascular beds are connected in parallel, and since flow through the carotid bifurcation is not hampered by ligation of the common carotid artery, our model permits the study of the effects of ipsilateral cervical sympathectomy on the cephalic vasculature. Materials and methodsThe experiments were performed with male rats (Chbb:THOM strain). Series III In animals with enophthalmos and ptosis the presence of miosis, the most important sign of sympathetic deficit, was demonstrated as follows: in four animals without dissection of the common carotid artery a preganglionic cervical sympathectomy was performed. After 9 to 50 days the animals were sedated (haloperidol 0-2 mg/kg body weight) and 30 minutes later both eyes were photographed after 60 s of complete darkness. We used an operating microscope and a light flash for photographic purposes. A series of six photographs was taken and the entire sequence was repeated twice. The greatest diameter of the pupil was measured on the prints. Series IVIn 18 unanaesthetised and unrestrained animals the following parameters were monitored before, during and for 80 minutes after carbon monoxide exposure (3000 ppm in room air, 70 minutes duration): systemic arterial blood pressure, heart rate, respiration rate, and EEG. For the recordings a slip ring assembly was used (for details cf ref 1). In seven of these animals the ipsilateral sympathetic chain had been divided.