Calcitonin gene-related peptide is present in mammalian cerebrovascular nerve fibres and dilates pial and peripheral arteries

Calcitonin gene-related peptide (CGRP) is a novel 37-amino acid peptide occurring in neurones within sensory ganglia, in brain stem, as well as in the walls of blood vessels of peripheral organs. Pial arteries of cat showed a well-developed supply of CGRP-positive nerve fibres. The peptide was found to be a potent dilator of both pial and peripheral vessels of rabbit and cat, and of pial vessels from man. The dilatory effect was independent of the vascular endothelium and was not mediated through adrenergic, cholinergic or histaminergic smooth muscle receptors. The neurogenic vasoconstriction induced by electrical field stimulation was temporarily inhibited by CGRP, as studied in central ear arteries from rabbits. The results suggest that CGRP is a transmitter or modulator playing a role in the regulation of vascular tone.     

The distribution pattern of the sympathetic nerve fibers to the cerebral arterial system in rat as revealed by anterograde labeling with WGA-HRP

Summary To clarify the projection route and the expansion of the terminal plexus of the sympathetic nerve fibers innervating the cerebral arterial system in rat, we labeled the postganglionic fibers originating in the superior cervical ganglion and traced their entire course by anterograde labeling with wheat germ agglutinin-horseradish peroxidase. Sympathetic innervation of the internal cerebral artery by labeled fibers actually began just at the portion where it enters the intradural space, and innervated it up to the small pial arteries located in the subarachnoid space, but not the intracerebral arterioles. On the main arteries in the circle of Willis, bundles of nerve fibers ran parallel to the long axis of the vessels and branched perpendicularly their terminal twigs with regular intervals to form a rib-structure pattern. On the arterial branches derived from the circle of Willis, a fine nerve bundle and delicate terminal axons formed a meshwork instead of a rib-structure pattern. These observations confirmed the existence of differences in the distribution pattern of the nerve plexus, which strongly affects the strength and quality of vasoconstriction by sympathetic activation in each level of the cerebral arterial system.     

大鼠椎动脉基底动脉系脑血管神经肽Y能神经与星状神经节、颈上神经节的关系

应用免疫组织化学技术 ABC法和神经节切除术 ,观察了大鼠脑底血管椎动脉、基底动脉系主要动脉分支神经肽 Y能神经纤维的起始核团。正常组大鼠脑底血管椎动脉颅内段、基底动脉和小脑上动脉均可见棕褐色的神经肽 Y能免疫反应阳性纤维 ,呈细线状 ,攀附于血管壁上。手术 I组作左侧星状神经节切除术 ,术后存活 7～ 10 d,左侧椎动脉颅内段阳性纤维基本消失 ,基底动脉和双侧小脑上动脉阳性纤维明显减少 ;右侧椎动脉颅内段阳性纤维无减少。手术 II组作双侧星状神经节切除术 ,双侧椎动脉颅内段、基底动脉和小脑上动脉阳性纤维基本消失。手术 III组作左侧颈上神经节切除术 ;手术 IV组作双侧颈上神经节切除术 ,上述各动脉阳性纤维密度未发现减少现象。手术 I、II组各组纤维密度数据与正常组者比较进行了统计学分析 ,P<0 .0 5。结果提示 :大鼠一侧星状神经节发出的神经肽 Y能神经纤维分布于同侧椎动脉颅内段、基底动脉和双侧小脑上动脉 ,即大鼠脑血管椎 -基底动脉系神经肽 Y能神经纤维主要起源于星状神经节 ,而与颈上神经节关系不大     

Nerve fibers surrounding intracranial and extracranial vessels from human and other species contain dynorphin-like immunoreactivity

Dynorphin B(20-32) was visualized by immunohistochemistry in guinea-pig and rat perivascular nerve fibers and was measured by radioimmunoassay within the walls of feline, canine, bovine and human cephalic and systemic arteries and veins. Canine vessels contained the highest levels. When human blood vessels or trigeminal ganglia were subjected to reverse-phase high-performance liquid chromatography, dynorphin immunoreactivity exhibited a retention time identical to that of synthetic dynorphin B. No differences in dynorphin-like immunoreactivity were measurable between feline systemic arteries and veins, or between cephalic and systemic vessels. The highest amounts were present in leptomeninges devoid of large pial arteries. Relatively high levels were also measured in feline and human trigeminal ganglia and feline superior cervical and sphenopalatine ganglia, three sources of projecting perivascular axons. Levels did not diminish, however, in ipsilateral feline cephalic vessels following either unilateral trigeminal or superior cervical ganglionectomies. Hence, dynorphin-containing fibers may project from parasympathetic cell bodies or perhaps from intrinsic brain sources. Previously published reports indicate that the kappa agonist dynorphin does not modify vessel tone when added in vitro but does inhibit release of neurotransmitters from afferent and sympathetic axons via prejunctional receptors. These observations suggest a pharmacological role for dynorphin on sensory and autonomic functions of the vasculature.     

Comparative study on the innervation of nerves with calcitonin gene-related peptide, substance P and neurokinin A immunoreactivity in the walls of the cerebral arteries of small bats (Mammalia: Microchiroptera).

The distribution and origin of nerves with calcitonin gene-related peptide, substance P or neurokinin A immunoreactivity in the walls of the cerebral arteries were investigated in three microchiropteran species. The supply of nerves immunoreactive for substance P and neurokinin A to the bat cerebral arteries is confined mostly to the vertebral and basilar arteries. The density of innervation of calcitonin gene-related peptide-immunoreactive nerves and that of nerves with substance P or neurokinin A immunoreactivity in the vertebrobasilar system differ among species: the Japanese large footed bat is innervated with nerves with calcitonin gene-related peptide, substance P and neurokinin A immunoreactivity with about the same density, whereas in the greater horseshoe bat, there are many substance P-immunoreactive nerves with very weak or no calcitonin gene-related peptide immunoreactivity, and in the bent-winged bat, calcitonin gene-related peptide immunoreactivity is not found in all nerves with substance P immunoreactivity in the pial arteries of all parts of the brain. Nearly all cells immunoreactive for substance P, calcitonin gene-related peptide or both in the trigeminal and cervical dorsal root ganglia were small. In the greater horseshoe bat and the bent-winged bat, there is a correlation between the level of expression of substance P and calcitonin gene-related peptide immunoreactivity in the cervical dorsal root and trigeminal ganglia and the cerebral perivascular nerves supplying the vertebrobasilar system. The cerebrovascular innervation of nerves with substance P immunoreactivity in small bats is similar to that of cats and guinea-pigs in which the trigeminal ganglia have been destroyed. These observations, in addition to absence of nerve cells showing substance P or calcitonin gene-related peptide immunoreactivity in the pial artery and in the nerve bundles accompanying the extracranial internal carotid and vertebral arteries, suggest that substance P-immunoreactive nerves with or without immunoreactivity to calcitonin gene-related peptide in the vertebrobasilar system of small bats originate exclusively from the cervical dorsal root ganglia. The remaining fibres probably originate in the trigeminal ganglia.     

A morphometric study of the effect of bilateral cervical sympathetic ganglionectomy on the architecture of pial arteries in spontaneously hypertensive and normotensive rats

The influence of the cranial sympathetic nerves on the architecture of pial arteries in normo- and hypertension was examined. For this purpose the effect of bilateral superior cervical ganglionectomy was evaluated in normotensive rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). The operations were performed at the age of 1 wk, which is just prior to the onset of ganglionic transmission. The length of the inner media contour was measured and the media cross-sectional area was determined planimetrically, with computerized digitalization of projected photographic images of transversely sectioned pial arteries. Four wk after sympathectomy there was a 20% reduction in media cross-sectional area and a consequent reduction in the ratio between media area and calculated luminal radius in the major pial arteries at the base of the brain in WKY but not in SHRSP. Conversely, in small pial arteries linear regression analysis showed that in WKY subjected to ganglionectomy the relationship between media cross-sectional area and luminal radius was significantly larger in arteries with a radius less than 21 μm compared to untreated WKY. No such effect was seen in the corresponding SHRSP vessels. In addition, the cross-sectional area of the internal elastic membrane (IEM) in the basilar arteries of WKY was measured by means of a computerized image-analysing system. Mean cross-sectional area of the IEM was approximately 45% larger following SE than in control animals. The present findings propose a ‘trophic’ role for the sympathetic perivascular nerves in large pial arteries of the rat. The increased media-radius ratio in the small pial arteries of the WKY following sympathectomy might reflect a compensatory hypertrophy due to reduced protection from the larger arteries against the pressure load. The inability to detect any morphometrically measurable effect of the sympathectomy in the cerebral arteries of SHRSP is probably explained by a marked growth-stimulating effect of the high pressure load in these animals.     

Neuropeptide Y: Immunocytochemical localization to and effect upon feline pial arteries and veins in vitro and in situ

Plexuses of nerve fibres containing neuropeptide Y (NPY)-like immunoreactivity invest pial arteries belonging to the circle of Willis, pial arterioles, occasionally penetrating arterioles and large veins. A more sparse supply of NPY-like fibres are observed around pial veins and venules. The NPY-immunoreactive fibres are located within the adventitia or at the adventitia-media border. Only occasional fibres are present in cerebral vessels of animals in which the superior cervical ganglion has been removed one week previously. Administration of NPY resulted in strong, concentration-dependent contractions of isolated feline middle cerebral arteries whereas administration of avian pancreatic polypeptide (APP) elicited weak contractions. In chloraloseanaesthetized cats, perivascular microapplication of NPY in situ resulted in marked concentration-dependent contractions of cerebral pial arterioles (34.7±6.6%; maximum decrease in calibre with NPY. Perivascular administration of NPY resulted in the constriction of pial veins but the magnitude of the venous calibre reductions was smaller than the response of arterioles at each reductions was smaller than the response of arterioles at each concentration examined. APP did not elicit contraction of pial arterioles or veins during in situ conditions. The pharmacological and immunocytochemical results strongly indicate the existence of a novel perivascular neuronal system containing NPY, which mediates contraction of cerebral blood vessels and NPY is colocalized with NA in sympathetic nerves.     

Effect of sympathetic nerve stimulation and adrenoceptor blockade on pial arterial and venous calibre and on intracranial pressure in the cat

Pial arterial and venous calibre were continuously recorded through a closed cranial window preparation during cervical sympathetic nerve stimulation in 10 cats before and after alpha- and beta-adrenoceptor blockade. In addition, the intracranial pressure (ICP) was simultaneously recorded in 4 of the cats. Under resting conditions 33 arteries (mean diameter 130 micron) constricted by 11.7 +/- 0.8% and 80 venous portions (mean diameter 152 micron) constricted by 13.7 +/- 0.7% during sympathetic nerve stimulation. ICP decreased simultaneously by 16.5 +/- 6.2%. Administration of the alpha-adrenoceptor antagonist phenoxybenzamine i.v. (1.5 mg X kg-1) abolished the reduction of ICP and markedly reduced, but did not completely abolish, the constrictor response of arteries and veins. The beta-adrenoceptor antagonist propranolol (1.5 mg X kg-1) did not significantly alter the reduction of ICP or the response of pial veins and small arteries, whereas the response of arteries with a diameter greater than 150 micron was attenuated. It is concluded that the constriction of pial veins and arteries during sympathetic stimulation is mediated predominantly via alpha-adrenoceptors. The sympathetic nerves of cerebral blood vessels may have stronger influence on the cerebral capacitance than on resistance vessels under normotensive and normocapnic conditions.     

Vascular autonomic nerves and corresponding receptors in brain vessels

Cerebral blood vessels, arteries and veins, are invested with a dense plexus of perivascular nerve fibres containing noradrenaline, acetylcholine esterase vasoactive intestinal polypeptide (VIP), substance P and avain pancreatic polypeptide (APP). The majority of the noradrenaline and APP-containing fibres disappear within one week after sympathectomy, while the other nerve fibres remain. Pharmacological studies of feline pial arteries in vitro have shown the presence of alpha 2- and beta 1- adrenoreceptors mediating contraction and dilatation, respectively. Dilatation can also be obtained by acetylcholine activating muscarinic receptors and by VIP and substance P.     

Neuropeptide Y co-exists with vasoactive intestinal polypeptide and acetylcholine in parasympathetic cerebrovascular nerves originating in the sphenopalatine, otic, and internal carotid ganglia of the rat

Neuropeptide Y co-exists with noradrenaline in the majority of the sympathetic nerves supplying cerebral blood vessels. However, after sympathectomy in the rat the number of cerebrovascular neuropeptide Y nerve fibers are only reduced in number despite a complete disappearance of the adrenergic markers. The origin of these non-sympathetic neuropeptide Y fibers was studied by nerve transections and retrograde axonal tracing utilizing True Blue. Three days after bilateral superior cervical sympathectomy, the number of neuropeptide Y-containing nerve fibers decreased to about 40% of that in non-treated animals. One week after True Blue application on the proximal portion of the middle cerebral artery, the tracer accumulated in neurons of the sphenopalatine, otic, and internal carotid ganglia. Of these cells 80%, 95% and 5%, respectively, were neuropeptide Y-positive. Some of the True Blue/neuropeptide Y-positive cells displayed immunoreactivity for vasoactive intestinal polypeptide and some were positive for choline acetyltransferase. Two weeks after bilateral removal of the sphenopalatine ganglion or transection of postganglionic fibers from the ganglion reaching the pial vessels through the ethmoidal foramen, together with subsequent sympathectomy, no neuropeptide Y-containing nerve fibers could be observed on the anterior cerebral and internal ethmoidal artery or the distal portion of the middle cerebral artery, whereas a few nerve fibers remained on the proximal portion of the middle cerebral artery, internal carotid artery, and the rostral portion of the basilar artery. In conclusion, neuropeptide Y in cerebrovascular nerves is co-stored not only with noradrenaline in sympathetic nerves from the superior cervical ganglion, but also with acetylcholine (reflected in the presence of choline acetyltransferase) and vasoactive intestinal polypeptide in parasympathetic nerves originating in the sphenopalatine, otic, and internal carotid ganglia.     

Hindbrain neurovascular anatomy of adult goldfish (Carassius auratus)

The goldfish hindbrain develops from a segmented (rhombomeric) neuroepithelial scaffold, similar to other vertebrates. Motor, reticular and other neuronal groups develop in specific segmental locations within this rhombomeric framework. Teleosts are unique in possessing a segmental series of unpaired, midline central arteries that extend from the basilar artery and penetrate the pial midline of each hindbrain rhombomere (r). This study demonstrates that the rhombencephalic arterial supply of the brainstem forms in relation to the neural segments they supply. Midline central arteries penetrate the pial floor plate and branch within the neuroepithelium near the ventricular surface to form vascular trees that extend back towards the pial surface. This intramural branching pattern has not been described in any other vertebrate, with blood flow in a ventriculo‐pial direction, vastly different than the pial‐ventricular blood flow observed in most other vertebrates. Each central arterial stem penetrates the pial midline and ascends through the floor plate, giving off short transverse paramedian branches that extend a short distance into the adjoining basal plate to supply ventromedial areas of the brainstem, including direct supply of reticulospinal neurons. Robust r3 and r8 central arteries are significantly larger and form a more interconnected network than any of the remaining hindbrain vascular stems. The r3 arterial stem has extensive vascular branching, including specific vessels that supply the cerebellum, trigeminal motor nucleus located in r2/3 and facial motoneurons found in r6/7. Results suggest that some blood vessels may be predetermined to supply specific neuronal populations, even traveling outside of their original neurovascular territories in order to supply migrated neurons.     

CEREBRAL FORM OF VON WINIWARTER-BUERGER'S DISEASE – REPORT OF AN AUTOPSY CASE –

A 35-year-old housewife suffered from disorders of the central nervous system since 23 years of age. Autopsy revealed multifocal infarcts distributed widely in the cerebrum and cerebellum. The small pial arteries related to infarctions showed proliferation of loose connective tissue in the intlma and of elastic fibers, and hyperplasia of endothelia, by which the arteries were occasionally occluded. It has been difficult to differentiate this condition from arteriosclerosis or other vascular diseases, but the pathological and clinical features have been found to be a little different in some points.     

Origin and distribution of cerebral vascular innervation from superior cervical, trigeminal and spinal ganglia investigated with retrograde and anterograde WGA-HRP tracing in the rat

Peripheral sources of cerebral vascular innervation have been investigated with retrograde and anterograde neuronal tracing of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) in the rat. For retrograde identification of sources of innervation, WGA-HRP was applied to the exposed basilar artery through a fine slit in the overlying meninges, and sections of brain and peripheral ganglia were reacted with tetramethylbenzidine for detection of the tracer. A high density of tetramethylbenzidine reaction product was observed around the basilar artery and in the surrounding pial tissue, but the application sites were not completely selective since some tracer always had spread into the ventral brain stem. Retrogradely labelled cell bodies were identified in the superior cervical, stellate, first and second spinal, and trigeminal ganglia, i.e. these ganglia may represent origins of basilar artery innervation. In a second series of experiments, microinjections of WGA-HRP were placed into the indicated ganglia to obtain anterograde labelling of nerve fibres on whole-mounts of the cerebral vessels. Injections into trigeminal ganglia labelled nerve fibres on the ipsilateral half of the circle of Willis, as well as the contralateral anterior cerebral artery and the rostral part of the basilar artery. The first and second spinal ganglia projected to the vertebrobasilar arteries, while the ipsilateral part of the internal carotid (outside the circle of Willis) received fibres from the second spinal ganglion. Nerve fibres originating in trigeminal and spinal ganglia were organised in bundles, and between these a sparse plexus of thin single fibres appeared. Injection of WGA-HRP into superior cervical ganglion labelled a plexus of nerve fibres on the ipsilateral circle of Willis and the (rostral) basilar artery. These experiments demonstrated the origin and distribution of sympathetic and sensory innervation to major cerebral arteries in the rat.     

Neuropeptide Y (NPY)-like immunoreactive nerve fibers in the human and monkey (Macaca fascicularis) kidney

Nerve fibers immunoreactive for neuropeptide Y (NPY) are demonstrated for the first time by the indirect immunofluorescence technique in the human and monkey kidney. NPY-like immunoactivity (NPY-LI) is shown in a bundle of nerve fibers in the surrounding connective tissue of arteries and to a lesser extent, veins, mainly at the juxtamedullary region. Varicose nerve terminals are shown associated with blood vessels and passing between tubules in the mid and lower cortex. NPY-LI nerve fibers are also seen surrounding afferent and occasionally efferent arterioles at the vascular pole of the glomeruli. The distribution of NPY-LI nerve fibers in the monkey and human kidneys is similar to that of other species, only the quantity of the nerve fibers varies.     

Cholinergic innervation of pial arteries in senescent rats: an immunohistochemical study.

Perivascular acetylcholine (ACh)-immunoreactive nerve fibres were demonstrated in basilar and middle cerebral arteries, in pial arteries and arterioles and in intracerebral arteries of male Fisher 344 rats of 6 months (young), 15 months (adult) and 22 months (senescent). Analysis included whole mounts of basilar and middle cerebral arteries, of pial arteries and sections of brain including pia-arachnoid membrane to demonstrate the localization of nerve fibres throughout the wall of pial and of intracerebral arteries. ACh-immunoreactive nerve fibres were demonstrated by indirect immunohistochemistry using a polyclonal anti-ACh antibody and their relative density was quantified. Perivascular ACh-immunoreactive nerve fibres were located in basilar and middle cerebral arteries, in pial arteries and arterioles and in intracerebral arteries. These fibres were found in the adventitia and adventitia-media border with a higher density in pial rather than in intracerebral arteries. A decrease of ACh-immunoreactive nerve fibres was observed both in pial and intracerebral arteries of adult or senescent rats compared to younger cohorts. The direct demonstration of ACh-immunoreactive nerve fibres in the cerebrovascular tree may contribute to evaluate the influence of experimental and pathological conditions on cerebrovascular cholinergic neuroeffector mechanisms, including a role of cholinergic innervation in the pathophysiology of cerebrovascular disease of the elderly.     

Indoleaminergic mechanisms in brain vessels; localization, concentration, uptake and in vitro responses of 5-hydroxytryptamine

Immunocytochemical studies have revealed the presence of 5-HT-containing nerve fibres in all parts of the cerebrovascular bed (arteries, arterioles and veins) of mouse, rat, guinea-pig, rabbit and cat. Biochemical measurements (using HPLC) revealed substantial concentrations of 5-HT and 5-HIAA in the pial vessels of the rat, rabbit, cat and man, the amounts corresponding well with the density of the perivascular nerve supply. The uptake of 3H-5-HT was studied in arteries removed from the circle of Willis in rats. Maximum uptake was reached after 15 min of incubation at 37 degrees C and plateaued at 30 min. The reaction was temperature-dependent and found to be absent if performed at 0 degrees C. Pharmacological experiments on isolated middle cerebral and basilar arteries showed that vessels from rat and dog were contracted by approximately 90% upon administration of 5-HT, whereas vessels from guinea-pig, rabbit, cat and man were contracted by 40 to 60% relative to 124 mM K+. The EC50 values in the different species varied by between 1.5 X 10(-7) M (rat) and 3 X 10(-9) M (dog). The 5-HT-induced contractions were blocked by the 5-HT antagonists, methysergide, methergoline and ketanserin. Transmural nerve stimulation (TNS) of the rabbit basilar artery revealed a tetrodotoxin sensitive constriction whereas TNS of cat and dog middle cerebral arteries caused a tetrodotoxin-sensitive relaxation. The relaxation was not significantly attenuated until high doses of methergoline (3 X 10(-6) M) or ketanserin (3 X 10(-5) M) had been given.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postnatal development of the vascular pattern in the rat telencephalic pia-arachnoid

Summary The postnatal changes in arrangement of the vascular system of the pia-arachnoid of rats are described based on scanning electron microscopy of microcorrosion casts and transmission electron microscopy. At birth, the distal arteries and veins are embedded in a dense plexiform network of immature capillaries. Arteries and veins are interconnected by many small capillary anastomoses. The trunks are located above the pial plexus. The underlying plexiform vessels provide the matrix for the formation of additional collateral and precortical segments during further development. During the first postnatal week, the distal pial arteries and veins become visible as separate channels and emerge from the subjacent capillary plexus. The pattern of anastomosing arterial rings is now clearly visible. The pial arterial tree can be subdivided into conductive, collateral, and precortical distributive segments, according to Jokelainen et al. (1982). Subsequently, passive expansion of the vascular system takes place during the period of rapid brain growth. In young adults the majority of the formerly closed arterial rings are interrupted, possibly by regression of single collateral arterial segments (Fig. 6). The dense venous capillary plexus of the pia is maintained during the first eight days in spite of marked brain growth. The process of reduction of this capillary plexus starts at the arterial side and proceeds from proximal to distal segments of the veins during the second and third week. The capillary segments, which provide anastomosis between arterial and venous vessels, disappear at the same time as the regression of the dense venous capillary network. Two processes may biodify the architecture of the pial vasculature during development: brain growth and maturation on the one side and cytodifferentiation of vascular walls on other.This work was presented in part at the Third World Congress for Microcirculation, Oxford, 9–14 September 1984, and was published in abstract form (1984, Int J Microcircul Clin Exp 3:308)     

Morphogenesis of the posterior inferior cerebellar artery with three-dimensional reconstruction of the late embryonic vertebrobasilar system

The posterior inferior cerebellar artery (PICA) shows the most variable course among the cerebellar arteries, mainly at the level of the lateral medullary segment. Based on the correlation between the level of origin and the characteristics of the lateromedullary segment, we have proposed three patterns of course of the PICA. With the aim of understanding their embryological basis we review the interrelations between the developing cerebellum and the primitive hindbrain arterial plexus through the analysis of transverse serial sections of human embryos of 22.5 and 23 mm crown-rump length. Three-dimensional reconstruction of the vertebrobasilar system has been performed to study the morphology of the vascular networks. The cerebellar primordium is vascularized by the metencephalic plexus that will form the basilar artery and the superior cerebellar arteries. Due to the development of the pontine flexure the rhomboid lips approach and the cerebellum comes into contact with the myelencephalon; thus the myelencephalic plexus represents an acquired source of vascularization for the cerebellum with respect to the metencephalic plexus. The examination of the transverse sections shows that the vertebral and basilar arteries, superior cerebellar arteries, anterior inferior cerebellar arteries, and primitive lateral vertebrobasilar anastomoses are well recognizable. The three-dimensional reconstruction of the vessels shows that the PICA is not yet defined due to the persistence of a plexus of many thin vessels at the level of the lateral aspect of the myelencephalon, indicating that its origin and course are established at the end of the embryonic period. Based on the evolution of the primitive hindbrain plexus, we suggest that in synchrony with the progressive descent of the cerebellum the branches of the myelencephalic plexus succeed with a rostrocaudal progression in feeding the cerebellum and the morphogenesis of the PICA results from the selection of portions of this plexus. The high origin of the PICA from the basilar artery could be ascribed to its development from a rostral collateral of the plexus due to an early development of the vessel at the beginning of its embryonic lifetime. Moreover, the three patterns of course of the PICA could reflect the variable retention of the primitive lateral vertebrobasilar anastomosis in the trunk of the definitive PICA, which may be related to its level of origin.     

Localization of the m5 muscarinic cholinergic receptor in rat circle of Willis and pial arteries

The expression and microanatomical localization of the muscarinic cholinergic m5 receptor subtype was investigated in rat circle of Willis and pial arteries by in situ hybridization, immunoblotting and immunohistochemistry. In situ hybridization histochemistry revealed a strong signal in the endothelium of circle of Willis and pial arteries and a moderate signal in the tunica media of the same arteries, within smooth muscle. Exposure of membranes of arteries to anti-m5 receptor protein antibodies caused the development of a band of approximately 81 kDa. Immunohistochemistry revealed the accumulation of m5 receptor protein immunoreactivity primarily within endothelium of circle of Willis and cerebral arteries and to a lesser extent in the tunica media, within smooth muscle. Medium (external diameter 200-100 microm) and small-sized (external diameter smaller than 100 microm) pial arteries displayed a significantly higher immune staining than large-sized pial arteries or circle of Willis arteries. The above data that are consistent with recent functional studies reporting cholinergic dilation of cerebral blood vessels mediated via a m5 receptor, have shown that both endothelial and muscular components of cerebral arteries synthesize and express a muscarinic m5 receptor. In view of the peculiar localization in cerebral vessels, handling of the muscarinic m5 receptor may be considered as an approach in the treatment of cerebrovascular disease.     

Changes of calcitonin gene-related peptide-like immunoreactivity in cerebrovascular nerve fibers in the dog after experimentally produced subarachnoid hemorrhage

After producing a model of subarachnoid hemorrhage (SAH) by a single injection of fresh autologous arterial blood into the cisterna magna in the dog, we immunohistochemically examined changes of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in perivascular nerve fibers in the large pial arteries by using whole mount preparations. CGRP-LI in cerebrovascular nerve fibers was suppressed after SAH. The suppression was first detected on the 3rd day after SAH, and was most marked during the 7th to 14th day after SAH. CGRP-LI, however, recovered to a normal level by the 42nd day after SAH.