SUMMARY A subarachnoid haemorrhage (SAH) in the rat was produced by the injection of blood via a previously implanted catheter connected to the cisterna magna. Repeated angiographical examinations of the vertebro-basilar arteries revealed a biphasic vasospasm with a maximal acute spasm at ten minutes and a maximal late spasm at two days after cisternal blood injection. Fluorescence microscopical examination of the major cerebral arteries at day two after the SAH revealed a reduction in the fluorescence intensity and in the number of histochemically visible sympathetic nerve terminals. Stroke Vol 16, No 4, 1985 CEREBRAL VASOSPASM is an angiographically demonstrable, variable arterial constriction that can be clinically asymptomatic or give rise to increasing neurological deficits or death. Vasospasm frequently occurs following a subarachnoid haemorrhage (SAH) secondary to rupture of an intracranial aneurysm. The mechanism underlying the development of spasm is not known.Research has focused on the discovery of a spasmogenic factor. Monoamines'~6 and prostaglandins 7 " 9 have been proposed as spasm inducing factors. Breakdown products of erythrocytes'°~1 2 and free radicals 13 -M have also been suggested. Correspondingly, monoamine antagonists or inhibitors have been used to prevent or treat vasospasm. l5~19 The effect of thromboxane synthetase inhibitors and prostacyclin on spasm has also been investigated. 2021 However, there is still no definitive treatment for spasm.In our opinion, there is a need for a simple and inexpensive SAH model giving a reproducible vasospasm in the investigation of the mechanism underlying the spasm syndrome. Therefore, we have developed a SAH model in the rat. This communication presents the angiographical data, and the results of the fluorescence microscopical examinations of the major cerebral arteries following a SAH. Materials and MethodsEighty-seven Sprague-Dawley rats weighing between 300 and 425 g were used. Animal PreparationsStage I. The animals were anaesthetized with chloral hydrate (250 mg/kg i.p.). An opaque x-ray catheter was inserted into the cisterna magna for subsequent injection of blood. The proximal part of the catheter was blunted and attached to the atlanto-occipital membrane with a purse string suture. The distal tip of the catheter was sealed and sutured subcutaneously to an external skull muscle. Stage II. Three to seven days after the implantation of the cisternal catheter, the animals were prepared for angiography. The anaesthesia was initiated with 4% halothane. The trachea was exposed and a tube (premature Infant feeding tube size 8 -CR Bard International Ltd., England) was inserted orally and observed entering the trachea. Respiration was controlled in a semiopen circuit using a servoventilator (manufactured at the University Hospital, Lund, Sweden). Anaesthesia was maintained with 70% nitrous-oxide and 30% oxygen.Catheters were inserted into a femoral artery and vein for continuous blood pressure monitoring and for infusion of drugs, respectiv...

Summary:The central projections of the nerve fibers in nervating the middle cerebral and basilar arteries were investigated by transganglionic tracing of wheat germ ag glutinin conjugated with horseradish peroxidase (WGA HRP) in the rat. WGA-HRP was applied to the exposed basilar and/or middle cerebral arteries. Sections of the brain, trigeminal and upper spinal ganglia were reacted with tetramethylbenzidine for detection of the tracer. The results demonstrate that trigeminal neurons that inner vate the middle cerebral artery project to the trigeminal main sensory nucleus, pars oralis, and the dorsocaudal two-fifths of pars interpolaris of the trigeminal brain stem nuclear complex. Te rminals were also visible in the ipsi lateral nucleus motorius dorsalis nervi vagi (dmnX) and in the lateral nucleus tractus solitarius (nTs) bilaterally at the level of the obex. The ventral periaqueductal gray, including the dorsal raphe and C2 dorsal horn, were also innervated by nerve fibers from the middle cerebral ar tery. Ipsilateral trigeminal rhizotomy prior to WGA-HRP application over the middle cerebral artery impeded the 54visualization of nerve terminations throughout the brain stem. Pretreatment with capsaicin reduced the density of labeled neurons and terminals within the trigeminal gan glion and the brain stem, respectively, following WGA HRP application over the middle cerebral artery. Basilar artery fibers terminate in the C2 dorsal horn, the cuneate nuclei, dmnX, and nTs bilaterally. A few projections were also labeled in the ventral periaqueductal gray. Uni lateral upper two spinal dorsal rhizotomy prior to WGA HRP application over the exposed basilar artery resulted in terminal labeling within the C2 dorsal horn, the cuneate nucleus, dmnX, and nTs contralateral to the rhizotomy, whereas the ipsilateral side was devoid of any labeling. Bilateral superior cervical ganglionectomy prior to WGA-HRP administration to the middle cerebral and basilar arteries did not alter the visualization of nerve ter minations throughout the brain stem.

Summary: A double-isotope technique for the simulta neous measurement of CBF and CMRglu was applied to a subarachnoid hemorrhage (SAH) model in the rat. Cis ternal injection of 0.07 ml blood caused a rather uniform 20% reduction in CBF together with an increase in glu cose utilization of 30% during the late phase of vaso spasm. In one-third of the SAH animals, there were focal areas where the flow was lowered to 30% of the control values and the glucose uptake increased to �250% of control. We suggest that blood in the subarachnoid space via a neural mechanism induces the global flow and meta bolic changes, and that the foci are caused by vasospasm superimposed on the global flow and metabolic changes. In the double-isotope autoradiographic technique,

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A double-isotope autoradiographic technique was used to evaluate CBF and glucose metabolism 2 days after a subarachnoid hemorrhage (SAH) in rats with lesions in the lower brainstem. Lesioning in the mesencephalon of the ascending catecholamine pathways from locus ceruleus and from the A1 and A2 nuclei, or lesioning in the medulla oblongata of the ascending fibers from A1 and A2, prevents the development of the global changes in flow and metabolism seen in normal animals post SAH. Also the focal low-flow areas with markedly elevated deoxyglucose uptake, which can develop in normal animals 2 days post SAH, were not seen in the lesioned animals after the SAH. The findings indicate that the A1 and A2 nuclei, which project to the hypothalamus-pituitary, are essential for the flow and metabolic changes after an SAH. The lesions per se did not change baseline flow and metabolism as compared with sham-lesioned animals.