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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,

Using immunohistochemistry, we studied the origins and pathways of parasympathetic and sensory nerve fibers to the pial arteries in four squirrel monkeys. Following its application to the surface of the middle cerebral artery, the retrograde axonal tracer True Blue accumulated in parasympathetic neurons of the sphenopalatine ganglion and the internal carotid ganglion. The latter is strategically located where the internal carotid artery enters the cranium. Fibers from the sphenopalatine ganglion reach the internal carotid artery in the cavernous sinus region after running as rami orbitales. Before reaching the internal carotid artery, the fibers bypass aberrant sphenopalatine ganglia, with the most distant, the cavernous ganglion, being located in the cavernous sinus region. True Blue also accumulated in sensory neurons of the ophthalmic and maxillary divisions of the trigeminal ganglion and in sensory neurons of the internal carotid ganglion. Fibers from the ophthalmic division of the trigeminal ganglion reach the internal carotid artery as a branch through the cavernous sinus, bypassing the cavernous ganglion. Fibers from the maxillary division also bypass the cavernous ganglion after reaching it via a recurrent branch of the orbitociliary nerve. Thus, the cavernous ganglion forms a confluence zone for parasympathetic and sensory fibers in the region. In addition, parasympathetic and sensory fibers leave the confluence zone to follow the abducent and trochlear nerves backward to the basilar artery and tentorium cerebelli, respectively. Clinical implications are discussed. (Stroke 1991^2:331-342) B lood vessels of the brain surface, and to some extent those of its parenchymal branches, are supplied with sympathetic, parasympathetic, and sensory nerve fibers, spreading like a network in the adventitia.1 It has been long known that all sympathetic fibers (except those in the caudal basilar artery in some species) originate in the superior cervical ganglion.1 An origin for parasympathetic fibers in the sphenopalatine and otic ganglia has been demonstrated in rats and cats by the retrograde axonal tracer technique, by nerve section, and by histochemical mapping of the putative transmitters acetylcholine (cholinesterase, choline acetyltransferase [ChAT]) and vasoactive intestinal polypeptide (VIP).2 -5 By this latter technique (histochemical staining of the putative transmitters substance P and calcitonin geneFrom the

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The contractile response to endothelin has been examined in cerebral arteries from rats subjected to a prior subarachnoid haemorrhage (SAH) and compared with saline-injected controls. Endothelin elicited concentration-dependent contractions of rat basilar artery segments. The endothelin-induced contractions were much stronger in the SAH compared to control animals, which suggests a role in the pathophysiology of cerebral vasospasm.

To analyze the brainstem projections of the innervation to the middle cerebral artery (MCA) in the squirrel monkey, transganglionic tracing of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) was used. After application of WGA-HRP to the middle cerebral artery (MCA), labelled cell bodies were identified in the ipsilateral trigeminal and superior cervical ganglia. In the brainstem, positive labelling indicative of preterminals and terminals occurred in a discontinuous pattern throughout the trigeminal brainstem nuclear complex. At the level of the obex, nerve terminations were identified in the nucleus tractus solitarius, nucleus motorius dorsalis nervi vagi and the nucleus nervi hypoglossi. Positive WGA-HRP profiles were also observed in the periaqueductal gray matter.

Intracisternal injection of blood in the rat induces an angiographically demonstrable, biphasic cerebral vasospasm of the vertebrobasilar system, with a maximal acute spasm at 10 min and a maximal late spasm at 2 days after the subarachnoid hemorrhage (SAH). Selective lesioning of the A1 nuclei in the medulla oblongata prior to the SAH prevents the development of the late spasm, but the acute spasm develops to the same extent as in sham-lesioned animals. Lesions of the medullary A2 nuclei not only prevent the development of both acute and late spasm, but give rise to a dilatation of the vertebrobasilar arteries at day 2 post-SAH. The study indicates that both the A1 and A2 nuclei participate in the development of vasospasm post-SAH. The contrasting patterns of spasm after A1 and A2 lesions suggest a different mechanism for acute and late spasm.