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Biomedical subjects

M B Vincent

Publications and source records attributed to M B Vincent.

At least 19 recordsLinked to original sources
PubMed1999

Primary headache care delivery by nonspecialists in Brazil. Brazilian Headache Care Cooperative Group.

Headaches are common disorders usually examined by nonneurologists. In order to assess how primary headache patients (IHS groups 1, 2, and 3) are generally managed by nonspecialists, 414 patients were asked about their previous headache care. Correct diagnosis had previously been made in only 44.9%, 6.7%, and 26.7% of the migraine, tension-type headache, and cluster headache patients, respectively. The patients underwent 501 investigative procedures motivated by the headache, averaging 1.21 examinations per patient, mostly EEGs. Preventive treatment was largely overlooked irrespective of the headache type. It is concluded that scientific improvements in headache care may be ineffective unless educational programs improve headache knowledge in general.

Adolescent↗
PubMed1999

Cervicogenic headache: a comparison with migraine and tension-type headache.

Cervicogenic headache (CEH) is a neck-generated headache syndrome. Attacks may be similar to migraine (M) or tension-type headache (TTH). In order to test the accuracy of the IHS diagnostic criteria for M and episodic TTH and of the criteria for CEH of Sjaastad et al., 33 CEH, 65 M, and 29 TTH were evaluated according to the CEH criteria, and CEH patients were tested for M and TTH according to the IHS criteria. Only 30% of the CEH patients met the criteria for M, 3% met the criteria for TTH, and 66% were neither M nor TTH. The mean number of criteria met, sex, age, and age of onset were also analysed, and the results indicate an inequality among these three headache types. The most important differentiating aspects were the site and radiation of the pain, the temporal pattern, and the induction of attacks from neck posture, movements, and/or digital pressure. CEH clearly differs from M and TTH. Existing criteria adequately distinguish the three headaches.

Adult↗
PubMed1998

Greater occipital nerve blockade in cervicogenic headache.

Cervicocogenic headache (CeH) is a relatively common disorder. Although on ideal treatment is available so far, blockades in different structures and nerves may be temporarily effective. We studied the effects of 1-2 mL 0.5% bupivacaine injection at the ipsilateral greater occipital nerve (GON) in 41 CeH patients. The pain is significantly reduced both immediately and as long as 7 days after the blockade. The improvement is less marked during the first two days, a phenomenon we called "tilde pattern". GON blockades may reduce the pool of exaggerated sensory input and antagonize a putative "wind-up-like effect" which may explain the headache improvement.

Analysis of Variance↗
PubMed1998

[Physiopathology of migraine].

The pathophysiology of migraine is not yet fully understood. The most important structures involved seem to be the central nervous system (cortex and brain stem), the trigeminovascular system and related cranial arteries, other autonomic fibres innervating such vessels, and various local vasoactive agents, including SP, CGRP, NO, VIP, NPY, ACh, NA, NKA, among others. The spreading depression phenomenon may explain clinical as well experimental findings in migraine. Its propagation velocity mirrors what is found in clinical aura, it may activate the spinal trigeminal nucleus and may induce CGRP and NO release. Circulatory changes detected with various imaging procedures during migraine also support the pathophysiological role of spreading depression. Three abnormal loci (chromosomes 1 and 19) have been recently found in familial hemiplegic migraine. This produces abnormalities in the voltage-dependent P/Q Ca channel, specific for the central nervous system, which regulates the release of various neurotransmitters, probably including serotonin. It is possible that a channelopathy underlies the pathophysiology of migraine, as in other paroxysmal neurological disorders secondary to membrane hyperexcitability.

Humans↗
PubMed1997

Sumatriptan blocks spreading depression in isolated chick retina.

Spreading depression is a neurohumoral phenomenon that has been related to the pathophysiology of migraine. The recently introduced 5HT1D agonist anti-migraine compound sumatriptan blocks neurogenic extravasation and induces cerebral vasoconstriction, but the actual mechanism of action against migraine remains obscure. Retinal spreading depression (RSD) velocity has been measured in isolated chick retinas in the presence of 0.05-2.00 mM sumatriptan. This drug reversibly blocks RSD in a concentration-dependent manner. Since the preparation is blood-vessel free, this effect must be related to the nervous tissue.

Animals↗
PubMed1997

On the pathogenesis of headache following TIA.

Twelve out of 49 patients with single or multiple transient ischemic attacks (TIAs) had TIA-related headaches, mostly in close temporal relation to the ischemic onset. Headache predominated in patients taking vasodilators when TIA occurred or with orthostatic hypotension at the first clinical examination, but atrial hypertension or a personal history of migraine were not more frequent in patients with headache. The site of the pain did not correlate with the presumed territory of cerebral ischemia. Pain during TIA is conceivably due to an interaction between cerebral vessels and the surrounding nervous system. Blood vessels have a sturdy physiological role concerning blood flow regulation, with receptors and signaling molecules potentially involved with pain production. Reflex mechanisms should justify pain in other areas.

Adult↗
PubMed1997

Computerized analysis of isometric tension studies provides important additional information about vasomotor activity.

Concentration-response curves of isometric tension studies on isolated blood vessels are obtained traditionally. Although parameters such as Imax, EC50 and pA2 may be readily calculated, this method does not provide information on the temporal profile of the responses or the actual nature of the reaction curves. Computerized data acquisition systems can be used to obtain average data that represent a new source of otherwise inaccessible information, since early and late responses may be observed separately in detail.

Animals↗
PubMed1996

Vasoactivity mediated by endothelin ETA and ETB receptors in isolated porcine ophthalmic artery.

Endothelin isopeptides and sarafotoxin S6b induced strong contractions in isolated porcine ophthalmic artery at basal tension, which were antagonized in a concentration-dependent manner by the specific ETA antagonist FR 139317. The maximum contraction and potency of endothelin-1 and sarafotoxin S6b were similar, whereas endothelin-3 was significantly less potent and induced weaker contractions. Schild plot analysis was only obtained for endothelin-1 and sarafotoxin S6b, but indicated competitive binding at the same ETA receptor site for these peptides. However, the slope obtained for endothelin-1 was significantly less than unity, suggesting more than one receptor. FR 139317 was a more potent antagonist of contractions induced by endothelin-3 than the other peptides. In arteries pre-contracted by prostaglandin F2 alpha high endothelin-3 concentrations induced additional contraction, except in the presence of FR 139317 when a marked relaxation was observed, an ability which was otherwise marked by the strong contractile activity. The relaxation was significantly reduced in endothelin-denuded segments. Both contraction and relaxation were abolished by the ETA/B antagonist bosentan. The results suggest the presence of ETB as well as ETA receptors in this artery type, though ETB receptor activity is only demonstrated at an unusually high concentration of endothelin in this preparation in vitro.

Animals↗
PubMed1995

Vasodilation in porcine ophthalmic artery: peptide interaction with acetylcholine and endothelial dependence.

Co-activation of cranial perivascular sensory and parasympathetic fibres in vivo induces simultaneous release of several vasodilatory substances with neurotransmitter or neuromodulatory roles. The role of the endothelium and possible interactions between such substances are poorly understood. The objective of this study was therefore to investigate these aspects with the sensory dilator calcitonin gene-related peptide (CGRP) and the parasympathetic dilators acetylcholine (ACh) and vasoactive intestinal peptide (VIP) in isolated porcine ophthalmic artery. Whilst ACh induced relatively rapid, endothelium-dependent dilation, CGRP and VIP induced slower dilations. Both CGRP and VIP were found to have partial endothelium-dependence in this artery. The simultaneous addition of ACh with CGRP potentiated the relaxation induced by CGRP, as has already been shown for substance P. ACh did not potentiate VIP relaxation, but the results generally indicate a potential role for ACh in initiating rapid dilation prior to strong, sustained relaxation by CGRP or VIP. The potential role of the endothelium and of substances like ACh or substance P in enhancing the rate of dilation of neuropeptides inducing strong and sustained relaxation is discussed.

Acetylcholine↗
PubMed1993

Sumatriptan relaxes isolated porcine ophthalmic artery, but inhibits VIP-induced relaxation.

Sumatriptan, a 5-hydroxytryptamine (5HT)1-like receptor agonist, is a new antimigraine drug which is also effective in cluster headache (CH), a disorder with marked ocular circulatory abnormalities. Sumatriptan could putatively exert a therapeutic effect in this vascular bed. The present study is an attempt to assess sumatriptan's vasoactivity in isolated porcine ophthalmic artery (POA) and to verify whether it has similar activity to 5HT, and whether it interferes with the vasodilation induced by calcitonin gene-related peptide (CGRP) and vasoactive intestinal peptide (VIP). In contrast to 5HT, sumatriptan induced only slight contraction in POA at high concentrations. However, in some artery segments pre-contracted with PGF2 alpha, sumatriptan induced a slight and short-lasting but marked relaxation. In addition, relaxations induced by VIP were inhibited significantly by sumatriptan, whereas CGRP effects were not influenced by the drug. Such reactions suggest that sumatriptan's effect in CH is probably unrelated to direct ocular arterial vasoconstriction.

Animals↗
PubMed1992

Mutual modification of vasoactivity by calcitonin gene-related peptide and endothelin-1 in isolated porcine ophthalmic artery.

Vasodilation has been implicated in the pathophysiology of some headaches, but the mechanisms behind such abnormalities remain unknown. Calcitonin gene related peptide (CGRP), a peptide present in sensory trigeminal fibres, induces strong and long lasting vasodilation in cranial vessels, and has been found to be increased in jugular blood during migraine attacks. Endothelin (ET) is a recently identified potent vasoconstrictor peptide, which also induces long-lasting responses. ET-CGRP interactions may be of importance in vascular beds putatively involved in pain development in the head, and were therefore studied in isolated porcine ophthalmic arteries. Both peptides were found to induce strong and long-lasting reactions in this artery. CGRP decreased ET-induced contractions and ET decreased CGRP-induced relaxations. These effects were additive rather than synergistic.

Animals↗
PubMed1992

Substance P augments the rate of vasodilation induced by calcitonin gene-related peptide in porcine ophthalmic artery in vitro.

Peptides may function as neurotransmitters liberated antidromically by sensory nerve fibres, provoking vascular responses having potential importance in some neurological disorders. Dose-response relaxation curves induced by substance P (SP) and calcitonin gene related peptide (CGRP) have been studied in porcine ophthalmic arteries in vitro. Both peptides induced vasodilation when tested separately (CGRP much greater than SP). Because of the putative interactions between such peptides in this vascular territory, a computerised system was also used for analysing over time the response to a single addition of either 10(-8) M CGRP, 10(-8) M SP or a combination of 10(-8) M SP + 10(-8) M CGRP. SP did not augment the maximum relaxation induced by CGRP alone, but increased significantly the rate of relaxation during the initial phase of the response. The effect induced by the SP+CGRP combination was stronger than the sum of the individual SP and CGRP-induced relaxations during the first 4 min of the response, which suggests a SP-CGRP synergism in this artery.

Animals↗
PubMed1992

Cyclooxygenase inhibitors modify the relaxant effect of vasoactive intestinal polypeptide and substance P in isolated porcine ophthalmic artery.

The absolute indomethacin effect in some unilateral headaches may, at least partially, be cyclooxygenase inhibition-independent. Aspirin and indomethacin, for example, may inhibit the neurogenically induced plasma extravasation in rat dura mater. Given the putative involvement of trigeminal neuropeptides in the pathophysiology of these conditions, the influence of cyclooxygenase inhibitors (indomethacin, acetylsalicylic acid (ASA) and naproxen) has been studied upon substance P, calcitonin gene-related peptide and vasoactive intestinal peptide (VIP)-induced vasodilatation in PGF2 alpha precontracted porcine ophthalmic arteries in vitro. None of the cyclooxygenase inhibitors significantly altered the effects of calcitonin gene-related peptide. The 10(-10) mol/l VIP-induced relaxation was inhibited significantly by all three cyclooxygenase inhibitors. Substance P-induced relaxation (from 10(-10) to 10(-8) mol/l) was enhanced by ASA and inhibited both by naproxen and, to a lesser extent, by indomethacin. The results suggest mainly that VIP-induced relaxations, particularly at lower concentrations, may be inhibited by all three cyclooxygenase inhibitors, and that naproxen, to a greater extent than aspirin or indomethacin, showed a tendency to inhibit vasodilatation induced by all peptides.

Animals↗
PubMed1992

Cluster headache: phospholipid metabolism in polymorphonuclear cells.

Our group has previously reported significant changes in the incorporation of precursors into glycerophospholipids, particularly phosphatidylserine, in polymorphonuclear cells obtained from the peripheral blood of cluster headache patients, when compared with controls. The potential of these results led to further work using both the previous methodology and a modified isolation technique to obtain polymorphonuclear cells in as pure a state as possible. Neither the new results obtained using the original technique, nor the results with high purity polymorphonuclear cells from controls and cluster headache patients, confirm the marked changes in precursor uptake into glycerophospholipids originally reported.

Adult↗
PubMed1992

Reduction of calcitonin gene-related peptide in jugular blood following electrical stimulation of rat greater occipital nerve.

Although it is known that pain in the forehead may be induced by neck abnormalities, the actual neck-head connections responsible for development of pain in trigeminal areas are poorly understood. Vasoactive neuropeptides released from sensory fibres, such as substance P (SP) and calcitonin gene-related peptide (CGRP), have been considered as important elements in headache pathophysiology. The levels of CGRP-like immunoreactivity (LI) were measured bilaterally in the jugular blood (52 rats) and intraocular aspirates (66 rats) following electrical stimulation of the left greater occipital nerve, and in the jugular blood of 13 control animals. One-third of the stimulated rats had varying combinations of conjunctival injection, tearing, diminished eye aperture and miosis or mydriasis on the stimulated side. The other two-thirds exhibited no ocular signs. Significantly lower levels of CGRP-LI were present in the jugular blood on the stimulated side in comparison with control rats. There was comparatively lower CGRP-LI on the non-stimulated side as well, but to a lesser extent. Significant differences between the stimulated and the non-stimulated side were present, particularly in the tearing/diminished eye cleft group. It is proposed that stimulation of the rat GON inhibits the trigeminal system (reduction of CGRP-LI) and possibly activates parasympathetic fibres (ocular changes).

Animals↗
PubMed1992

Lithium inhibits substance P and vasoactive intestinal peptide-induced relaxations on isolated porcine ophthalmic artery.

Lithium is currently a major drug used as a treatment for affective disorders and cluster headache, among other conditions. Its mechanism of action remains unknown. The trigeminovascular system may be involved in the pathophysiology of cluster headache and related diseases by liberating neuropeptides such as substance P (SP) and calcitonin gene-related peptide (CGRP) in the eye-forehead region. The objective of this study was to investigate whether or not a low concentration of lithium may interfere with peptidergic neuro-transmission at this level. Vasoactive intestinal peptide (VIP), SP, CGRP, capsaicin, and SP+CGRP concentration-response relaxation curves were obtained in the presence and absence of 2 x 10(-4) M lithium in isolated porcine ophthalmic arteries. Lithium inhibited the SP and VIP, but not the CGRP responses. Capsaicin-(a neurotoxin causing release of stored sensory neuropeptides) induced relaxations were partially inhibited by lithium. It is concluded that lithium may interfere with SP- and VIP-induced relaxation. If SP and VIP are of pathogenic significance in cluster headache, lithium may possibly work by counteracting unwanted effects of such peptides.

Animals↗
PubMed1992

Low concentrations of lithium and cyclooxygenase inhibitors enhance endothelin-1 (ET-1)-induced contractions in human temporal artery, but not in porcine ophthalmic artery.

Endothelins are a recently discovered group of potent vasoconstrictor peptides synthesized by endothelial cells and other tissues in various species, which seem to participate in the regulation of vascular tonus. Abnormalities in vasoactivity in the head may be an important event in headache pathophysiology, although the mechanisms responsible for such constrictions and/or dilations are not known. The endothelium and its constrictor peptide, endothelin, may play a key role in such mechanisms. Of the various drugs used in the treatment of headache, lithium is an accepted treatment for cluster headache, and indomethacin is the drug of choice for the associated condition chronic paroxysmal hemicrania. The mechanism of action of these drugs in these headaches is not known. Due to the possible involvement of endothelin in headache disorders, the objective of this study was to verify the effects of lithium and cyclooxygenase inhibitors (indomethacin, acetylsalicylic acid and naproxen) on endothelin-1 (ET-1)-induced contractions in isolated human temporal arteries and porcine ophthalmic arteries. It was found that all drugs increased the (ET-1)-induced contractions in human temporal arteries. Conversely, there were no significant changes induced by the drugs in porcine ophthalmic arteries. These results are consistent with the variation of activity often seen in different vascular beds and between species. The potential importance of such reactions for the understanding of vascular changes putatively involved in headache development and treatment is discussed.

Animals↗