Changes of neuropeptide immunoreactivity in cerebrovascular nerve fibers after experimentally produced SAH. Immunohistochemical study in the dog

Both coiling and clipping induce the time-dependent release of endogenous neuropeptide Y into serum

Background

The vaso- and psychoactive endogenous Neuropeptide Y (NPY) has repeatedly been shown to be excessively released after subarachnoid hemorrhage and in numerous psychiatric disorders. NPY is stored in sympathetic perivascular nerve fibers around the major cerebral arteries. This prospective study was designed to analyze the impact of microsurgical and endovascular manipulation of the cerebral vasculature versus cranio- and durotomy alone on the serum levels of NPY.

Methods

58 patients (drop-out n = 3; m:f = 26:29; mean age 52.0 ± 14.1 years) were prospectively enrolled. The vascular group underwent repair for unruptured intracranial aneurysms (UIA) of the anterior circulation [endovascular aneurysm occlusion (EV) n = 13; microsurgical clipping (MS) n = 17]; in the non-vascular group, 14 patients received microsurgical resection of a small-sized convexity meningioma (CM), and 11 patients with surgically treated degenerative lumbar spine disease (LD) served as control. Plasma was drawn (1) before treatment (t0), (2) periprocedurally (t1), (3) 6 h postprocedurally (t2), (4) 72 h postprocedurally (t3), and (5) at the 6-week follow-up (FU; t4) to determine the NPY levels via competitive enzyme immunoassay in duplicate serum samples. We statistically evaluated differences between groups by calculating one-way ANOVA and for changes along the time points using repeated measure ANOVA.

Results

Except for time point t0, the serum concentrations of NPY ranged significantly higher in the vascular than in the non-vascular group (p < 0.001), with a slight decrease in both vascular subgroups 6 h postprocedurally, followed by a gradual increase above baseline levels until FU. At t3, the EV subgroup showed significantly higher NPY levels (mean ± standard deviation) than the MS subgroup (0.569 ± 0.198 ng/mL vs. 0.415 ± 0.192 ng/mL, p = 0.0217). The highest NPY concentrations were measured in the EV subgroup at t1, t3, and t4, reaching a climax at FU (0.551 ± 0.304 ng/mL).

Conclusion

Our study reveals a first insight into the short-term dynamics of the serum levels of endogenous NPY in neurosurgical and endovascular procedures, respectively: Direct manipulation within but also next to the major cerebral arteries induces an excessive release of NPY into the serum. Our findings raise the interesting question of the potential capacity of NPY in modulating the psycho-behavioral outcome of neurovascular patients.

Blood-Related Toxicity after Traumatic Brain Injury: Potential Targets for Neuroprotection

Emergency visits, hospitalizations, and deaths due to traumatic brain injury (TBI) have increased significantly over the past few decades. While the primary early brain trauma is highly deleterious to the brain, the secondary injury post-TBI is postulated to significantly impact mortality. The presence of blood, particularly hemoglobin, and its breakdown products and key binding proteins and receptors modulating their clearance may contribute significantly to toxicity. Heme, hemin, and iron, for example, cause membrane lipid peroxidation, generate reactive oxygen species, and sensitize cells to noxious stimuli resulting in edema, cell death, and increased morbidity and mortality. A wide range of other mechanisms such as the immune system play pivotal roles in mediating secondary injury. Effective scavenging of all of these pro-oxidant and pro-inflammatory metabolites as well as controlling maladaptive immune responses is essential for limiting toxicity and secondary injury. Hemoglobin metabolism is mediated by key molecules such as haptoglobin, heme oxygenase, hemopexin, and ferritin. Genetic variability and dysfunction affecting these pathways (e.g., haptoglobin and heme oxygenase expression) have been implicated in the difference in susceptibility of individual patients to toxicity and may be target pathways for potential therapeutic interventions in TBI. Ongoing collaborative efforts are required to decipher the complexities of blood-related toxicity in TBI with an overarching goal of providing effective treatment options to all patients with TBI.

Excessive release of endogenous neuropeptide Y into cerebrospinal fluid after treatment of spontaneous subarachnoid haemorrhage and its possible impact on self-reported neuropsychological performance - results of a prospective clinical pilot study on good-grade patients

OBJECTIVES

Neuropsychological dysfunction after treatment of spontaneous subarachnoid haemorrhage (sSAH) is common but underreported. The vasoconstrictor neuropeptide Y (NPY) is excessively released after sSAH and in psychiatric disorders. We prospectively analysed the treatment-specific differences in the secretion of endogenous cerebrospinal fluid (CSF) NPY during the acute stage after sSAH and its impact on cognitive processing.

METHODS

A total of 26 consecutive patients (f:m = 13:8; mean age 50.6 years) with good-grade sSAH were enrolled (drop out n = 5): n = 9 underwent endovascular aneurysm occlusion, n = 6 microsurgery, and n = 6 patients with perimesencephalic SAH received standardized intensive medical care. Ventricular CSF was drawn daily from day 1-10. CSF NPY levels were determined with competitive enzyme immunoassay. All patients underwent neuropsychological self-report assessment [36-Item Short Form Health Survey (SF-36) and ICD-10-Symptom-Rating questionnaire (ISR)] after the onset of sSAH (day 11-35; t₁) and at the 6-month follow-up (t₂).

RESULTS

At t₁, increased mean levels of NPY in CSF significantly correlated with impaired performance in most ISR scores (ISR total p = .018, depression p = .035, anxiety p = .008, nutrition disorder p = .047, supplementary items p = .038) and in several psychological SF-36 items (vitality p = .019, general mental health p = .001, mental component summary p = .025).

DISCUSSION

To the best of our knowledge, this study is the first to correlate the levels of endogenous NPY in supratentorial CSF with cognitive outcome in good-grade sSAH patients. Excessive NPY release into CSF may have a short-term influence on the pathogenesis of neuropsychological deficits. The impact of cerebrovascular manipulation on NPY release has to be further elucidated.

ABBREVIATIONS

ANOVA: analysis of variance; aSAH: aneurysmal subarachnoid haemorrhage; AUC: area under the curve; CBF: cerebral blood flow; CSF: cerebrospinal fluid; CT (scan): computed tomography (scan); CV: cerebral vasospasm; DIND: delayed ischemic neurological deficit; DSA: digital subtraction angiography; EIA: enzyme immunoassay; EV: endovascular aneurysm occlusion; EVD: external ventricular drainage; FU: 6-month follow-up; GCS: Glasgow Coma Scale; Ghp: general health perceptions; GOS: Glasgow Outcome Scale; h: hour/s; HH: Hunt and Hess; ICU: intensive care unit; ISR: ICD-10-Symptom-Rating questionnaire; MCS: mental component summary; Mhi: general mental health; min: minute/s; min-max: minimum - maximum; ml: millilitre; mRS: modified Ranking Scale; MS: microsurgical clipping, microsurgical aneurysm occlusion; ng: nanograms; no. [n]: number; NPY: Neuropeptide Y; p: p value; Pain: bodily pain; PCS: physical component summary; Pfi: physical functioning; pSAH: perimesencephalic subarachnoid haemorrhage; PTSD: posttraumatic stress disorder; QoL: quality of life; Rawhtran: health transition item; Rolem: role limitations because of emotional problems; Rolph: role limitations due to physical health problems; SAH: subarachnoid haemorrhage; SD: standard deviation; SF-36: 36-Item Short Form Health Survey; Social: social functioning; sSAH: spontaneous subarachnoid haemorrhage; TCD: trans-cranial Doppler ultrasound; (test) t₁: test in the sub-acute phase after the onset of bleeding (between day 11 and 35 after subarachnoid haemorrhage); (test) t₂: test in the short-term (chronic phase) after treatment at 6-month follow-up; test t₁ - t₂: intergroup development from t₁ to t₂; Vital: vitality; vs: versus.

Neuropeptide Y - an early biomarker for cerebral vasospasm after aneurysmal subarachnoid hemorrhage

OBJECTIVES

In the human brain, the potent vasoconstrictive neuropeptide Y (NPY) is abundantly expressed. Neuropeptide Y, which is stored in perivascular nerve fibers of the cerebral arteries, regulates the cerebral vascular diameter as well as cerebral blood flow. However, the role of NPY in the pathogenesis of cerebral vasospasm (CV) related to subarachnoid hemorrhage (SAH) is unclear. We prospectively analyzed and compared the release of endogenous NPY in the cerebrospinal fluid (CSF) of 66 patients with SAH to NPY release in a control group. Additionally, we correlated the levels of NPY with CV and consecutive ischemic stroke.

METHODS

Sixty-six consecutive patients (40 women, 26 men; mean age 53·1 years) with aneurysmal SAH were included. In the SAH group, CSF was drawn daily from day 1 to day 10 after the onset of SAH. The CSF of 29 patients undergoing spinal anesthesia for orthopedic surgery served as control samples. The NPY levels were determined in duplicate CSF samples by means of a competitive enzyme immunoassay (EIA). The levels of NPY in CSF were correlated with the development of CV over the 10-day period after the onset of SAH and to the occurrence of consecutive ischemic stroke. To evaluate CSF NPY levels as a predictive biomarker for vasospasm, we calculated the sensitivity and specificity as well as the positive and negative predictive values.

RESULTS

The NPY levels were significantly higher in the SAH group than in the control group (p < 0·001). The treatment modality (clip versus coil) did not influence the level of NPY in CSF (p > 0·05). Patients with CV showed significantly higher NPY levels than patients without CV during the entire observation period. The NPY levels of the non-CV group dissipated over time, whereas the CV group showed continuously increasing values. The NPY levels from day 4 to 10 were significantly higher in patients with CV-related stroke than in non-stroke patients. Using 0·3 ng/ml as a cut-off value, NPY levels on day 3 predicted the occurrence of CV with a sensitivity and specificity of 82% and 72%, respectively. High NPY levels, starting on day 4, significantly correlated with poor Glasgow Outcome Score grading at the follow-up (p < 0·05).

DISCUSSION

Our data indicate that NPY is involved in the pathogenesis of SAH-related CV and ischemia. Neuropeptide Y represents an early and reliable biomarker for the prediction of CV and consecutive stroke due to aneurysmal SAH.

The possible role of neuropeptide Y after spontaneous subarachnoid hemorrhage

OBJECTIVE

Neuropeptide Y (NPY), a highly potent vasoconstrictive neuropeptide, is widely expressed in the human brain, regulating vessel diameter and cerebral blood flow. Earlier studies focusing on the possible role of NPY in the context of aneurismal subarachnoid hemorrhage (SAH) and vasospasm have produced conflicting results. However, despite extensive research efforts, the pathophysiological mechanisms underlying the SAH-related vasospasm and delayed cerebral ischemia (DCI) have not been clarified. We, therefore, attempted to investigate the role of NPY in SAH-induced vasospasm in a larger, well documented patient population utilizing modern analytical tools. We focused on the release of the potent vasoconstrictor NPY in cerebrospinal fluid (CSF) and blood, and its correlation to vasospasm and stroke in the early clinical stage.

METHODS

Thirty-seven patients with SAH and a control group consisting of 29 patients were included. Eighteen patients developed stroke, 21 patients met the Doppler sonographical criteria for vasospasm. Twenty-nine patients had aneurysms of the anterior circulation and four patients of the posterior circulation. All patients had ventricular drainage inserted and an arterial catheter. Blood and CSF were drawn daily for NPY analysis during a 10-day interval.

RESULTS

The levels of NPY in CSF and plasma were significantly higher after SAH than in the control group (p = 0.001). The vasospasm group showed NPY levels in CSF which continuously ranged above the NPY levels of the non-vasospasm group (p = 0.001). Patients with stroke caused by vasospasm had significantly higher levels of NPY (p = 0.001).

DISCUSSION

NPY is released excessively into blood and CSF following SAH. Patients with cerebral infarction caused by vasospasm had significantly higher levels of NPY. Our results indicate a certain role for NPY in the pathophysiology of vasospasm due to SAH and justify further studies in this area of research.

Intracranial hemorrhage: mechanisms of secondary brain injury

ICH is a disease with high rates of mortality and morbidity, with a substantial public health impact. Spontaneous ICH (sICH) has been extensively studied, and a large body of data has been accumulated on its pathophysiology. However, the literature on traumatic ICH (tICH) is limited, and further investigations of this important topic are needed. This review will highlight some of the cellular pathways in ICH with an emphasis on the mechanisms of secondary injury due to heme toxicity and to events in the coagulation process that are common to both sICH and tICH.

Perivascular nerve damage in the cerebral circulation following traumatic brain injury

Traumatic brain injury (TBI) causes cerebral vascular dysfunction. Most have assumed that it was the result of endothelial and/or smooth muscle alteration. No consideration, however, has been given to the possibility that the forces of injury may also damage the perivascular nerve network, thereby contributing to the observed abnormalities. To test this premise, we subjected rats to impact acceleration. At 6 h, 24 h and 7 days post-TBI, cerebral basal arteries were removed and processed with antibody targeting protein gene product 9.5 (PGP-9.5), with parallel assessments of 5-hydroxytryptamine (5-HT) accumulation in the perivascular nerves. Additionally, Fluoro-Jade was also used as a marker of axonal degeneration. The perivascular nerve network revealed no abnormality in sham animals. However, by 6 h post injury, Fluoro-Jade reactivity appeared in the perivascular regions, with the number of fibers increasing with time. By 24 h post injury, a significant reduction in the perivascular 5-HT accumulation occurred, together with a reduction in PGP-9.5 fiber staining. At 7 days, a recovery of the PGP-9.5 immunoreactivity occurred, however, it did not reach a control-like distribution. These studies suggest that neurogenic damage occurs following TBI and may be a contributor to some of the associated vascular abnormalities.

Peptidergic and non-peptidergic innervation and vasomotor responses of human lenticulostriate and posterior cerebral arteries

The aim of the present study was to compare in man the innervation pattern and the functional responses to neuronal messengers in medium sized lenticulostriate and branches of the posterior cerebral arteries (PCA). The majority of the nerve fibers found were sympathetic and displayed specific immunoreactivity for tyrosine hydroxylase (TH) and neuropeptide Y (NPY). Only few nerve fibers displayed vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P (SP) immunoreactivity. In both arteries, the contractions induced by noradrenaline (NA), NPY and 5-hydroxytryptamine (5-HT) and the relaxant responses induced by acetylcholine (ACh), VIP and pituitary adenylate cyclase activating peptide-27 (PACAP) as well as CGRP and SP were compared in vitro. In conclusion, there was no major difference in innervation pattern or vasomotor sensitivity (pEC50 and pIC50 values) between the two vessels. However, the general pattern indicates stronger vasomotor responses (Emax and Imax) in the PCA branches as compared to the lenticulostriate arteries which may lend support for the clinical observation of a difference in stroke expression between the two vascular areas.

Cerebrovascular inflammation following subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage frequently results in complications including intracranial hypertension, rebleeding and vasospasm. The extravasated blood is responsible for a cascade of reactions involving release of various vasoactive and pro-inflammatory factors (several of which are purported to induce vasospasm) from blood and vascular components in the subarachnoid space. The authors review the available evidence linking these factors to the development of inflammatory lesions of the cerebral vasculature, emphasizing: 1) neurogenic inflammation due to massive release of sensory nerve neuropeptides; 2) hemoglobin from lysed erythrocytes, which creates functional lesions of endothelial and smooth muscle cells; 3) activity, expression and metabolites of lipoxygenases cyclooxygenases and nitric oxide synthases; 4) the possible role of endothelin-1 as a pro-inflammatory agent; 5) serotonin, histamine and bradykinin which are especially involved in blood-brain barrier disruption; 6) the prothrombotic and pro-inflammatory action of complement and thrombin towards endothelium; 7) the multiple actions of activated platelets, including platelet-derived growth factor production; 8) the presence of perivascular and intramural macrophages and granulocytes and their interaction with adhesion molecules; 9) the evolution, origins, and effects of pro-inflammatory cytokines, especially IL-1, TNF-alpha and IL-6. Human and animal studies on the use of anti-inflammatory agents in subarachnoid hemorrhage include superoxide and other radical scavengers, lipid peroxidation inhibitors, iron chelators, NSAIDs, glucocorticoids, and serine protease inhibitors. Many animal studies claim reduced vasospasm, but these effects are not always confirmed in human trials, where symptomatic vasospasm and outcome are the major endpoints. Despite recent work on penetrating vessel constriction, there is a paucity of studies on inflammatory markers in the microcirculation.

Effect of calcitonin gene-related peptide on delayed cerebral vasospasm after experimental subarachnoid hemorrhage in rabbits

BACKGROUND

Calcitonin gene-related peptide (CGRP) is an intrinsic vasodilatory substance contained in perivascular nerve fibers of intracranial arteries. It is suggested that CGRP plays a role in cerebral vasospasm after subarachnoid hemorrhage (SAH).

METHOD

An experimental SAH was produced by intracisternal injection of arterial blood in rabbits. The animals were treated with intrathecal administration of CGRP solution 3 days after SAH. The degree of vasospasm and the effect of CGRP were evaluated angiographically by measuring the basilar artery diameter.

RESULTS

The basilar artery constricted to 73.0% of the pre-SAH values 3 days after SAH. Fifteen minutes after injection of 10(-10) mol/kg CGRP, the basilar artery dilated to 117.1% (n = 8), which was significantly larger than 67.1% in the vehicle group (n = 8) (p < 0.01). The significant vasodilatory effect of CGRP, compared with the vehicle group, lasted for 6 hours.

CONCLUSIONS

Intrathecal administration of CGRP has therapeutic potential for treating cerebral vasospasm.

Cholinergic and vasoactive intestinal polypeptidergic innervation of the cerebral arteries

Acetylcholine and vasoactive intestinal polypeptide are not only two vasoactive agonists that predominantly induce a vasodilatation of the cerebral arteries, but also correspond to neurotransmitters that innervate the various anatomical segments of the cerebral vasculature. The distinct patterns of the cerebrovascular cholinergic and vasoactive intestinal polypeptidergic innervation, their neurochemistry, in vitro and in vivo pharmacology, as well as the putative pathophysiological implications of these neurotransmission systems are critically summarized on the basis of the most recently published literature.

Perivascular neuropeptides (NPY, VIP, CGRP and SP) in human brain vessels after subarachnoid haemorrhage

INTRODUCTION--Cerebral blood vessels are innervated by sympathetic nerve fibres storing neuropeptide Y (NPY), parasympathetic nerves storing acetylcholine, vasoactive intestinal peptide (VIP) and sensory afferent fibres containing calcitonin gene-related peptide (CGRP), substance P (SP) and neurokinin A. In experimental studies on subarachnoid haemorrhage (SAH) there are indications that perivascular peptides are involved. In the present study we have in man measured the levels of NPY, VIP, SP and CGRP in brain vessels of patients that have suffered a fatal SAH and compared this with the levels encountered in subjects that died of an extracerebral cause. MATERIAL AND METHODS--Vessels from patients who have died from SAH or nonSAH were obtained during autopsy performed within 24 hrs after death. The peptides were extracted and fractionated with reversed phase liquid chromatography (HPLC). The levels of NPY, VIP, SP, and CGRP were measured with radioimmunoassay. Vasomotor responses of human cerebral arteries were performed using a sensitive in vitro system. RESULTS--Human cerebral vessels contained NPY, VIP, CGRP and SP which eluted at the same positions as the authentic peptides. The level of CGRP was significantly lower (p < 0.01) in arteries removed from SAH patients as compared to control subjects. The level of SP was not changed, if anything it tended to be increased after SAH. The levels of NPY and VIP were not significantly altered after SAH. In isolated brain vessels alpha-CGRP was a potent vasodilator of arteries precontracted with whole blood, prostaglandin F2 alpha or endothelin. It had a poor effect on vessels precontracted with 60 mM potassium. CONCLUSION--The evidence suggest that the trigemino-cerebrovascular system, storing CGRP and SP, is to a differential degree involved in the pathophysiology of SAH in man and supports the hypothesis of an exhaustion of CGRP as one important factor in the development of late spasm occurring after SAH.

Effect of subarachnoid haemorrhage on trigeminovascular calcitonin-gene-related peptide and substance P of the rat dura mater versus cerebral vasculature

While the presence of a robust perivascular neural network accompanying cerebral and dural blood vessels that contain various neuropeptides is well documented, the functional significance of this innervation is unclear. Following experimentally induced subarachnoid haemorrhage (SAH) in animal models, immunocytochemical studies have revealed that changes occur in the staining intensity of some of these neuropeptides. This study compared the immunostaining intensity of calcitonin-gene-related peptide (CGRP) and substance P (SP) in cerebral and dural perivascular nerve fibers after SAH in the rat. Subarachnoid haemorrhage was produced by injecting 0.3 ml of autologous blood into the cisterna magna of male Sprague Dawley rats. Sham operated animals received an equal volume of buffered lactated Ringer's solution (pH 7.4). Changes in the immunostaining intensity of cerebral and dural vessels were evaluated by independent observers at 6, 24, and 48 hours after SAH. Immunostaining of CGRP was reduced in cerebral vessels at 6 hours and returned to normal by 48 hours. In contrast, CGRP immunostaining of dural perivascular nerve fibers was unchanged at all time periods examined. A marked decrease in SP immunostaining was documented at 6 hours in both the cerebral and dural vessels in all animals; at 48 hours, the staining intensity had returned to control levels. These results support the idea that several subpopulations of trigeminovascular neurons containing CGRP, SP, or both project to cerebral and dural vessels. Since these subpopulations may be differentially activated in pathologic conditions, such as SAH or vascular headache, the potential exists for pharmacologic intervention of specific neuropeptides with the resultant abatement of a pathologic process.

Effect of spantide, a substance-P antagonist, on cerebral vasospasm in primates

Experimental SAH in the squirrel monkey induces an angiographically demonstrable late spasm of about 23% at six days post subarachnoid haemorrhage (SAH). The late spasm is associated with a generalized reduction in cerebral blood flow (CBF) of about 30%. Intracisternal administration of the substance P (SP) antagonist spantide two hours and three days post SAH significantly reduces the degree of late spasm and also decreases the degree of CBF reduction. The findings suggest that SP is involved in the development of both angiographical spasm and CBF changes post SAH.

Dural neuropeptide changes after subarachnoid hemorrhage in rats

The effect of subarachnoid hemorrhage (SAH) on the neuropeptides and mast cells of the rat dura mater has not been reported. We examined the outcome of SAH on the rat supratentorial dura mater to determine whether dural nerves undergo effects similar to those of nerves accompanying cerebral blood vessels after SAH. Following the injection of fresh autologous arterial blood into the cisterna magna, animals were sacrificed at 6, 24, and 48 h, and 6 days post-SAH. Dural whole mounts were immunohistochemically reacted with antibodies to calcitonin gene-related peptide (CGRP), substance P (SP), neuropeptide Y (NPY), and serotonin (5-HT). SP-like immunostaining was substantially reduced after SAH and subsequently returned to control levels at 6 days. NPY-like fiber innervation of the dura was markedly reduced after SAH; although immunostaining intensity increased, it had not returned to control levels at 6 days. The 5-HT content of dural mast cells identified by immunostaining markedly decreased at 6 and 24 h and returned to control levels at 48 h. In contrast, CGRP immunostaining was unchanged in all experimental groups. One possible explanation for this differential response is that subpopulations of trigeminovascular neurons containing SP, CGRP, or CGRP and SP respond differently to various stimuli, including SAH. Another possibility is a differential release of SP or CGRP from the same fiber. To the best of our knowledge this is the first documentation that the dura is also a target for intracranial pathological processes, such as SAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain levels of neuropeptide Y in experimental pneumococcal meningitis

Neuropeptide Y (NPY), which is found in high concentrations in several regions of the brain including nuclei of the brain stem and in nerve fibers surrounding cerebral vessels, has been proposed to play a role in regulating cerebral blood flow (CBF) and systemic vegetative functions. Since CBF is altered during meningitis, we examined whether NPY concentrations changed in various regions of the rabbit brain in response to experimental pneumococcal meningitis. Changes were most pronounced in the medulla, where NPY concentration increased threefold after 48 h of infection. Concomitantly, there was an increase in NPY immunoreactive fibers surrounding small vessels in the dorsolateral medulla, especially in the nucleus tractus solitarius. These results suggest that NPY may play a role in inducing some of the hemodynamic changes seen during pneumococcal meningitis.

Neuropeptide Y in the primate model of subarachnoid hemorrhage

The cause of cerebral vasospasm after subarachnoid hemorrhage (SAH) remains unknown. Recently, an association between the potent vasoconstricting peptide, neuropeptide Y, and delayed cerebral vasospasm after SAH has been postulated. This was based on the findings of increased neuropeptide Y levels in the cerebrospinal fluid (CSF) and plasma after SAH in animals and humans. For this study, the primate model of SAH was used to assess the possible role of neuropeptide Y in delayed vasospasm after SAH. Fifteen cynomolgus monkeys underwent placement of a clot of either whole blood or red blood cells in the subarachnoid space around the middle cerebral artery (MCA). Sequential arteriography for assessment of MCA diameter and sampling of blood and CSF for neuropeptide Y were performed: before SAH (Day 0); 7 days after SAH, when signs of delayed cerebral vasospasm peak in this model and in humans; 12 days after SAH; and 28 days after SAH. Subarachnoid hemorrhage did not evoke changes in CSF or plasma levels of neuropeptide Y. Nine monkeys had arteriographic evidence of vasospasm on Day 7, but no change in neuropeptide Y levels occurred in plasma or CSF. In addition, neuropeptide Y levels did not change, even after resolution of vasospasm on Day 12 or Day 28. Neuropeptide Y levels were substantially higher in CSF than in arterial plasma (p less than 0.003 at each interval). No correlation was found between neuropeptide Y levels in CSF and in plasma. These results do not confirm a relationship between neuropeptide Y levels in the CSF or peripheral plasma and delayed cerebral vasospasm in SAH.

Chronic parasympathetic sectioning decreases regional cerebral blood flow during hemorrhagic hypotension and increases infarct size after middle cerebral artery occlusion in spontaneously hypertensive rats

Regional cerebral blood flow (rCBF) during controlled hemorrhagic hypotension (140-20 mm Hg) was assessed 10-14 days after chronic unilateral sectioning of parasympathetic and/or sensory fibers innervating pial vessels in spontaneously hypertensive rats (SHR). rCBF was measured in the cortical barrel fields bilaterally by laser Doppler blood flowmetry. Immunohistochemistry of middle cerebral artery (MCA) whole mount preparations was used to verify the surgical lesion. During hemorrhagic hypotension, rCBF was equivalent on the two sides in shams, after selective sensory denervation, or in parasympathetically sectioned animals exhibiting small decreases (less than or equal to 30%) in immunoreactive vasoactive intestinal peptide (VIP)-containing fibers. After chronic parasympathetic denervation, decreases in perfusion pressure were accompanied by greater reductions in rCBF on the lesioned side; changes in vascular resistance were also attenuated on that side. The rCBF response to hypercapnia (PaCO2 50 mm Hg), however, was symmetrical and robust. To examine the effects of impaired neurogenic vasodilation on the pathophysiology of cerebral ischemia, infarct size was measured 24 h following tandem MCA occlusion in denervated animals. Infarction volume was larger after selective parasympathetic sectioning (sham, 156 +/- 27 vs. 196 +/- 32 mm3, respectively) but only in those denervated animals demonstrating greater than or equal to 40% decrease in immunoreactive VIP-containing fibers within the ipsilateral MCA. Lower than expected blood flow/perfusion pressure in the cortex distal to an occluded blood vessel may relate the observed blood flow responses to the occurrence of larger cortical infarcts in parasympathetically denervated animals. If true, the findings suggest a novel role for neurogenic vasodilation in the pathophysiology of cerebral ischemia and in rCBF regulation within the periinfarction zone.

Changes in neuropeptide Y after experimental traumatic brain injury in the rat

We utilized a model of fluid percussion (FP) brain injury in the rat to examine the hypothesis that alterations in brain neuropeptide Y (NPY) concentrations occur following brain injury. Male rats (n = 44) were subjected to FP traumatic brain injury. One group of animals (n = 38) was killed at 1 min, 15 min, 1 h, or 24 h after brain injury, and regional brain homogenates were analyzed for NPY concentrations using radioimmunoassay. A second group of animals (n = 6) was killed for NPY immunocytochemistry. Concentrations of NPY in the injured left parietal cortex were significantly elevated at 15 min post injury (p less than 0.05). No changes were observed in other brain regions. NPY-immunoreactive fibers were seen at 15 min post injury predominantly in the injured cortex and adjacent hippocampus. These temporal changes in NPY immunoreactivity, together with previous observations concerning posttraumatic changes in regional CBF in these same areas, suggest that an increase in region NPY concentrations after brain injury may be involved in part in the pathogenesis of posttraumatic hypoperfusion.

Cerebrovascular effects of substance P after experimental subarachnoid haemorrhage

The vasoactive effects of substance P (SP), as well as the content of cyclic guanine monophosphate (cGMP), were determined in the rabbit basilar artery after subarachnoid haemorrhage (SAH). Out of 47 rabbits, 24 were subjected to a SAH, induced by injecting 5 ml of autologous arterial blood into the cisterna magna; 23 were used as controls. In 20 animals (10 SAH and 10 controls), isometric tension recording of isolated rings of the basilar artery--dissected 2 days after SAH--was employed to assess the dose-dependent vasodilatation to SP (10(-10) to 10(-6) M) after precontraction with serotonin (10(-8) to 10(-5) M). In 15 animals (8 SAH and 7 controls), the basal cGMP content was measured in the basilar artery 2 days after SAH. In the other 12 animals (6 SAH and 6 controls), the increase in cGMP content was measured in the basilar artery after a 10-minute incubation with SP (10(-6) M). SP caused significantly less dilatation in animals subjected to SAH than in controls, especially for concentrations between 10(-9) and 10(-6) M (p < 0.001). The cGMP content in the arteries 2 days after SAH was significantly lower than in control arteries (31.5 +/- 7.3 against 57.3 +/- 4.3 pmoles/g tissue). In the preparations incubated with SP, the increase of cGMP was 440 +/- 115% in the control arteries, and only 97 +/- 30% in the arteries after SAH. It is concluded that the vasodilator activity of SP is significantly impaired after SAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Depletion of calcitonin gene-related peptide in perivascular nerves during acute phase of posthemorrhagic vasospasm in the rabbit

The behaviour of various neuropeptides during early and late vasospasm following experimental subarachnoid hemorrhage has been investigated by several authors. Recently, a reduction of the content of vasodilatory neuropeptides (vasodilatory intestinal peptide, substance P and calcitonin gene-related peptide) has been demonstrated in the perivascular nerves of cerebral arteries after few days from induction of experimental subarachnoid hemorrhage. In the present immunohistochemical study, the authors investigated secretion and expression of CGRP a few minutes after injection of autologous blood into the cisterna magna of the rabbit. The authors propose that the marked decrease of calcitonin gene-related peptide immunoreactivity in the perivascular nerves, observed after experimental subarachnoid hemorrhage, is due to compensatory secretion of the peptide.

Parasympathetic denervation of rat pial vessels significantly increases infarction volume following middle cerebral artery occlusion

Studies were undertaken in Long Evans rats to examine the hypothesis that chronic unilateral sectioning of vasodilating nerve fibers (parasympathetic and/or sensory) innervating the circle of Willis increases infarction volume following unilateral branch occlusion of the middle cerebral artery (MCA) combined with temporary (45 min) bilateral common carotid occlusion. Infarct size was measured 24 h after surgical occlusion from seven coronal slices. Infarction volume (mean +/- SD) in sham animals (group A) and surgically naive animals (group B) measured 153 +/- 43 and 131 +/- 38 mm3, respectively. After lesions of both sensory (nasociliary nerve) and parasympathetic efferents at the ethmoidal foramen (group C, combined lesion) or selective lesions of parasympathetic efferents (group D), infarction volume increased [214 +/- 47 mm3 (p less than 0.01) and 209 +/- 46 mm3 (p less than 0.05), respectively]. No increases were detected after cutting the nasociliary nerve alone (group E) or occluding the external ethmoidal artery (group F) [145 +/- 39 mm3 (p greater than 0.05) and 124 +/- 63 mm3 (p greater than 0.05), respectively]. The infarct was predominantly located within cortical gray matter and became enlarged on its superior and inferior aspects after parasympathectomy. Large infarcts were noted whether animals breathed spontaneously (all of the above) or were artificially respired or whether animals were anesthetized with xylazine and ketamine or chloral hydrate. Taken together, these studies suggest a previously unrecognized protective role for autonomic parasympathetic fibers in the pathophysiology of focal cerebral ischemia that is not shared by sensory fibers. The importance of autonomic vasodilating fibers to blood flow in ischemic brain merits further study.

Chronic trigeminal ganglionectomy or topical capsaicin application to pial vessels attenuates postocclusive cortical hyperemia but does not influence postischemic hypoperfusion

Marked hyperemia accompanies reperfusion after ischemia in the brain, and may account for the propensity of cerebral hemorrhage to follow embolic stroke or carotid endarterectomy, and for the morbidity that follows head injury or the ligation of large arteriovenous malformations. To evaluate the contribution of trigeminal sensory fibers to the hyperemic response, CBF was determined in 12 symmetrical brain regions, using microspheres with up to five different isotopic labels, in four groups of cats. Measurements were made at 15-min intervals for up to 2 h of reperfusion after global cerebral ischemia induced by four-vessel occlusion combined with systemic hypotension of either 10- or 20-min duration. In normal animals, hyperemia in cortical gray matter 30 min after reperfusion was significantly greater after 20 min (n = 10) than after 10 min (n = 7) of ischemia (312 ml/100 g/min versus 245 ml/100 g/min; p less than 0.01). CBF returned to preischemic levels approximately 45 min after reperfusion and was reduced to approximately 65% of basal CBF for the remaining 75 min. In cats subjected to chronic trigeminal ganglionectomy (n = 15), postocclusive hyperemia in cortical gray matter was attenuated by up to 48% on the denervated side (249 versus 150 ml/100 g/min; p less than 0.01) after 10 min of ischemia. This effect was maximal in the middle cerebral artery (MCA) territory, and was confined to regions known to receive a trigeminal innervation. In these animals, substance P (SP) levels in the MCA were reduced by 64% (p less than 0.01), and the density of nerve fibers containing calcitonin gene-related peptide (but not vasoactive intestinal polypeptide or neuropeptide Y) was decreased markedly on the lesioned side. Topical application of capsaicin (100 nM; 50 microliters) to the middle or posterior temporal branch of the MCA 10-14 days before ischemia decreased SP levels by 36%. Postocclusive hyperemia in cortical gray matter was attenuated throughout the ipsilateral hemisphere by up to 58%, but the cerebral vascular response to hypercapnia (PaCO2 = 60 mm Hg) was unimpaired. The duration of hyperemia and the severity of the delayed hypoperfusion were not influenced by trigeminalectomy, capsaicin application, or the intravenous administration of ATP. These data demonstrate the importance of neurogenic mechanisms in the development of postischemic hyperperfusion, and suggest the potential utility of strategies aimed at blocking axon reflex-like mechanisms to reduce severe cortical hyperemia.

Origins and distribution of cerebrovascular nerve fibers showing calcitonin gene-related peptide-like immunoreactivity in the major cerebral artery of the dog

The origins and overall distribution of perivascular nerve fibers showing calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in the major cerebral arteries were investigated immunohistochemically in the dog by using whole-mount preparations of the arterial trees around the circle of Willis. Perivascular nerve fibers with CGRP-LI were seen most abundantly in the basilar artery, vertebral artery, common anterior cerebral artery, proximal part of the anterior cerebral artery, and terminal part of the internal carotid artery. They were far less numerous in the middle cerebral artery, posterior cerebral artery, superior cerebellar artery, and distal part of the anterior cerebral artery. Neuronal cell bodies with CGRP-LI were observed in the trigeminal, nodose, superior cervical, and dorsal root ganglia. CGRP-LI fibers in the large pial arteries in the circle of Willis were eliminated ipsilaterally after unilateral transection of the ophthalmic division of the trigeminal nerve, and slightly reduced in number ipsilaterally after unilateral transection of the maxillary division of the trigeminal nerve. They did not show any noticeable changes after unilateral transection of the mandibular division of the trigeminal nerve. On the other hand, CGRP-LI fibers in the basilar and vertebral arteries did not show any appreciable changes after unilateral transection of the trigeminal nerve, but they were eliminated after bilateral ganglionectomy of the dorsal root ganglia of the first, second, and third cervical nerves. After ganglionectomy of the ciliary, pterygopalatine, otic, nodose, or superior cervical ganglion, no changes were observed in perivascular nerve fibers with CGRP-LI in the major cerebral arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of cerebral vasospasm in the rat by depletion or inhibition of substance P in conducting vessels

Cisternal blood injection in the rat induces a biphasic angiographic vasospasm, with a maximal acute spasm at 10 minutes and a maximal late spasm at 2 days after the subarachnoid hemorrhage (SAH). Depletion of substance P-containing sensory nerves to the cerebral arteries with capsaicin prior to SAH prevents the development of both acute and late spasm. Intrathecal administration of the substance P antagonist spantide 2 hours prior to SAH also prevents the development of vasospasm, while spantide administration 1 hour before SAH only hinders the occurrence of late vasospasm. Intracisternal administration of spantide 2 hours post-SAH prevents the development of late vasospasm. This antagonist per se can induce a short-lasting dose-dependent angiographic vasoconstriction. Substance P-containing nerve fibers on the cerebral arteries could constitute the sensory link in a reflex arc system involved in the development of vasospasm in which the presence of blood in the subarachnoid space stimulates sensory substance P-containing nerve fibers on the cerebral arteries inducing a centripetal impulse to the A2-nucleus tractus solitarius setting into motion the events in the brain stem leading to acute and late vasospasm.

Vascular relaxation properties of calcitonin gene-related peptide and vasoactive intestinal polypeptide in subarachnoid hemorrhage

The vascular relaxation effects of calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP) on the dog basilar artery after experimentally produced subarachnoid hemorrhage (SAH) were examined in vitro by an isometric tension recording method. Both CGRP and VIP induced dose-dependent relaxations in ring segments of the intact basilar artery of control dogs. The vasorelaxant action of CGRP was more potent than that of VIP. The single-injection model of SAH was produced by injection of fresh autologous arterial blood (1 ml/kg body weight) into the cisterna magna on Day 0 of the post-SAH period, and the double-injection model was produced by two injections of blood (0.5 ml/kg each) on Days 0 and 2. Narrowing of the basilar arteries on vertebral angiograms was most prominent on Day 3 or 7 in the single- or double-injection model, respectively. Relaxation of the basilar artery induced by CGRP and VIP was to some extent decreased on Days 3 and 7 of the post-SAH period in the single-injection model, and on Days 7 and 14 in the double-injection model. However, the vasorelaxant effects of CGRP and VIP were significantly enhanced on Day 14 of the post-SAH period in the single-injection model, and on Days 28 and 42 in the double-injection model. Subsequently, these effects returned to control levels by Days 28 or 63 in the single- or double-injection model, respectively.

Erythrocytes suppress calcitonin gene-related peptide- and vasoactive intestinal polypeptide-like immunoreactivities in cerebrovascular nerve fibers after subarachnoid hemorrhage

Changes of calcitonin gene related-peptide (CGRP)- and vasoactive intestinal polypeptide (VIP)-like immunoreactivities (LI) in cerebrovascular nerve fibers on the dog basilar artery were immunohistochemically examined by using whole-mount preparations after single percutaneous injection of blood components into the cisterna magna. Blood components were prepared from autologous arterial blood. CGRP- and VIP-LI in cerebrovascular nerve fibers were highly suppressed after the injection of washed erythrocytes, but only moderately after the injection of platelet-rich or platelet-poor plasma. The results suggest that erythrocytes may suppress CGRP- and VIP-LI in cerebrovascular nerve fibers after subarachnoid hemorrhage.

Cholinergic and VIPergic innervation in cerebral arteries: a sequential double-labeling immunohistochemical study

The possible co-localization of choline acetyltransferase (ChAT) and vasoactive intestinal polypeptide (VIP) in the nerve fibers of cat cerebral arteries was examined by a sequential double-labeling immunohistochemical method. Diaminobenzidine and tetramethylbenzidine were used as chromogens to distinguish ChAT (protein) and VIP (peptide) immunoreactivities. Since available fixatives often did not provide simultaneous preservation of optimal protein and peptide immunoreactivities, a new fixative, buffered periodate-paraformaldehyde-picric acid-formaldehyde-lysine (PPPFL), was formulated and tested. PPPFL fixative is more reliable for simultaneously preserving ChAT and VIP immunoreactivities than were periodate-lysine-paraformaldehyde (PLP) fixative, Zamboni's fixative, or 2% paraformaldehyde solution alone. Using PPPFL as fixative, both ChAT immunoreactive (ChAT-I) and VIP-immunoreactive (VIP-I) fibers in cerebral arteries appeared as bundle and fine fibers. Most ChAT-I and VIP-I fibers were separate. Portions of ChAT-I and VIP-I fibers often ran closely in parallel or across each other. Overlaying of VIP-I on ChAT-I fibers and relay connections between them were also observed. These morphological data suggest the potential functional interactions between cholinergic and VIPergic innervations. In less than 5% of the fibers examined did ChAT and VIP immunoreactivities appear to be co-localized. These data therefore do not support the hypothesis that acetylcholine and VIP are co-localized in most fibers innervating the cerebral arterial wall.

Increased neuropeptide Y concentrations in cerebrospinal fluid from patients with aneurysmal subarachnoid hemorrhage

We investigated the possible relation between neuropeptides and cerebral vasoconstriction in samples of ventricular or cisternal cerebrospinal fluid from 14 patients with subarachnoid hemorrhage. Neuropeptide Y, calcitonin gene-related peptide, atrial natriuretic peptide, and pituitary polypeptide 7B2 were present in the cerebrospinal fluid of these patients. Concentrations of calcitonin gene-related peptide and 7B2 were not significantly different from those in control subjects, but that of atrial natriuretic peptide was significantly lower. Although the mean concentration of neuropeptide Y was not significantly higher than control, consecutive determinations showed an increase 6-11 days after the onset of subarachnoid hemorrhage. An initially high 7B2 concentration decreased gradually, although half the patients showed a second increase greater than 10 days after the onset. Considering the well-recognized vasoconstrictive effect of neuropeptide Y, it is possible that this increase in its concentration in the cerebrospinal fluid plays a role in the pathogenesis of the cerebral vasospasm that is often seen after subarachnoid hemorrhage.

Subarachnoid blood and headache: altered trigeminal tachykinin gene expression

Sensory axons from the trigeminal ganglion (V) innervate cephalic blood vessels and use the preprotachykinin gene products, substance P (SP) and neurokinin A (NKA), as putative neurotransmitters conveying nociceptive information. Blood in the subarachnoid space is accompanied by severe headache. We now report that this painful stimulus, which should enhance activity in V, specifically alters tachykinin peptide and mRNA levels in V and perivascular axons. Marked reductions in SP levels were observed in basilar artery segments within 4 hours after intracisternal blood injection which persisted for 48 hours and recovered by 7 days. SP peptide levels in V were elevated by 49% two days after blood injection. The changes in SP peptide levels were accompanied by increases in ganglionic content of the preprotachykinin mRNA that codes for the peptide. Blood-induced peptide depletion in arteries and subsequent increases in peptide and mRNA in V are consistent with increased neuronal activity and enhanced neuropeptide release. These results implicate the tachykinin-utilizing trigeminovascular neurons in the sequelae of subarachnoid hemorrhage.

Endothelium-dependent and -independent responses to vasodilators of isolated dog cerebral arteries

We compared responses to calcium ionophore A23187, vasopressin, and substance P in helical strips of dog middle cerebral, basilar, and posterior communicating arteries to obtain a better understanding of humoral control of cerebrovascular tone in different brain regions and its potential impact on mechanisms of cerebral vasospasm. A23187 relaxed these different arterial strips partially precontracted with prostaglandin F2 alpha to a similar extent. Vasopressin produced concentration-dependent relaxation in basilar and posterior communicating arterial strips, whereas middle cerebral arterial strips either contracted or relaxed slightly. Relaxations induced by A23187 and vasopressin were either abolished or converted to contractions by removal of the endothelium. In contrast, the relaxation of cerebral arterial strips to substance P was markedly attenuated but not abolished by endothelium denudation; the remaining relaxation was suppressed by indomethacin. In some cerebral arterial strips with intact endothelium, substance P caused a transient contraction that was reversed to a relaxation by indomethacin or ONO-3708, a prostaglandin antagonist. In arterial strips denuded of endothelium from the same dogs, substance P always produced relaxations. Relaxations of cerebral arterial strips to A23187 and vasopressin appear to be mediated by endothelium-derived relaxing factor. The function of vasopressin receptors in endothelial cells differs markedly in basilar and posterior communicating arteries versus middle cerebral arteries. Substance P-induced relaxations appear to be primarily associated with endothelium-derived relaxing factor and with prostaglandin I2, whereas contractions appear to be mediated by endothelium-derived prostaglandins.

Possible origins of cerebrovascular nerve fibers showing vasoactive intestinal polypeptide-like immunoreactivity: an immunohistochemical study in the dog

Changes of vasoactive intestinal polypeptide-like immunoreactivity (VIP-LI) in perivascular nerve fibers of the major cerebral arteries were examined immunohistochemically in the dog. The density of cerebrovascular nerve fibers showing VIP-LI (the average number of nerve fibers with VIP-LI in a unit area of the major cerebral arteries) was estimated, by using whole-mount preparations after extirpation of the pterygopalatine, otic or superior cervical ganglion. After pterygopalatine ganglionectomy, the density was markedly decreased in major cerebral arteries of both anterior circulation (the anterior cerebral and middle cerebral arteries) and posterior circulation (the basilar, superior cerebellar, posterior cerebral and posterior communicating arteries). After otic ganglionectomy, the density was moderately reduced in the major arteries of the posterior circulation, but was not decreased in those of the anterior circulation. After superior cervical ganglionectomy, the density was decreased markedly in the major cerebral arteries of the posterior circulation, and moderately in those of the anterior circulation. The results also indicate that the pterygopalatine, otic and superior cervical ganglia supply perivascular nerve fibers showing VIP-LI to the major cerebral arteries bilaterally with an ipsilateral dominance.

Changes of vasoactive intestinal polypeptide-like immunoreactivity in cerebrovascular nerve fibers after cervical sympathectomy in the dog

The presence of vasoactive intestinal polypeptide-like immunoreactivity (VIP-LI) was confirmed in many neuronal perikarya of the superior cervical ganglion (SCG), as well as in many perivascular nerve fibers of the major cerebral arteries in the dog. After bilateral extirpation of the SCG, VIP-LI was decreased markedly in the basilar artery and the posterior cerebral artery, and moderately in the middle and anterior cerebral arteries.