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Biomedical subjects

L Edvinsson

Publications and source records attributed to L Edvinsson.

At least 37 records · Page 2Linked to original sources

4991W93 inhibits release of calcitonin gene-related peptide in the cat but only at doses with 5HT(1B/1D) receptor agonist activity?

Calcitonin gene-related peptide (CGRP) is a marker for trigeminovascular activation and is released during the headache phase of migraine and cluster headache. CGRP may have a role in migraine through its potent cranial vasodilator effects, or by an action on trigeminal nerve activity, both of which are targeted by 5HT(1B/1D) agonist drugs. CP122,288, a conformationally restricted analogue of sumatriptan that is a potent inhibitor of neurogenic plasma protein extravasation (PPE), was ineffective at inhibiting CGRP release at a single low dose; and is also ineffective as an acute anti-migraine compound. However, it remained unclear as to whether, as a class, the conformationally-restricted triptan analogues could have inhibitory effects on CGRP in higher doses. 4991W93, a conformationally restricted analogue of zolmitriptan, is also a potent inhibitor of PPE at doses without 5HT(1B/1D)-mediated effects, that was developed as an anti-migraine drug, and thus was suitable to test whether higher doses of such conformationally restricted triptan analogues could inhibit trigeminal-evoked CGRP release. The superior sagittal sinus (SSS) was stimulated in 14 anaesthetised cats and external jugular vein blood samples were analysed by radioimmunoassay for CGRP levels before, 1 min after SSS stimulation, and 1 min after SSS stimulation in the presence of 4991W93. Stimulation of the SSS resulted in release of CGRP from the external jugular vein. 4991W93 at a dose of 0.1 and 10 microg/kg, selected for maximal PPE blocking effects in rodents, was ineffective at inhibiting CGRP release, with an SSS stimulation level of 78+/-4 pmol/l compared to a post-4991W93 level of 79+/-3 pmol/l (n=4). In comparison CGRP release was inhibited after a dose of 100 microg/kg 4991W93 from 64+/-6 to 36+/-3 pmol/l (n=5). Given that 4991W93 is inactive clinically at non-vascular doses, it seems clear that the 5HT(1B/1D) agonist effects of the compound are necessary for blockade of CGRP release and thus any anti-migraine action. Taken with the clinical results, these data emphasise the importance of CGRP release in migraine, and suggest that other non-5HT-based pharmacological targets may account for PPE blockade in animal studies.

Animals↗

Neuronal messengers in the human cerebral circulation.

In recent years our knowledge of the nervous control of the cerebral circulation has increased. The use of denervations and retrograde tracing in combination with immunohistochemical techniques has demonstrated that cerebral vessels are supplied with sympathetic, parasympathetic, and sensory nerve fibers and possibly central pathways containing a multiplicity of new transmitter substances in addition to the classical transmitters. The majority of these transmitters are neuropeptides. More recently it has been suggested that a gaseous transmitter, nitric oxide (NO) also could participate in the neuronal regulation of cerebral blood flow. Although little is known about the physiological actions and inter-relationships among all these putative neurotransmitters, their presence within cerebrovascular nerve fibers will make it necessary to revise our view on the mechanisms of cerebrovascular neurotransmission.

Humans↗

Enhanced Ca2+-induced contractions and attenuated alpha-adrenoceptor responses in resistance arteries from rats with congestive heart failure.

AIM: The aim of the present study was to examine the role of Ca2+-mediated contractile responses in isolated mesenteric resistance arteries from rats with congestive heart failure (CHF). METHODS: Heart failure was induced by ligation of the left coronary artery. Rats exposed to the same surgical procedure except ligation served as controls (Sham). The following experiments were conducted: (1) passive increase in radial stretch (the length-tension relationship) in Ca2+-free and in depolarizing high K+-solution; (2) the contractile responses to external application of Ca2+ and high K+-solutions in the presence of nifedipine and phentolamine; and (3) a histological evaluation of CHF and Sham vessels. RESULTS: The length-tension induced response in Ca2+-free buffer solution was significantly lower in arteries from CHF rats, starting at a very low tension (0.9+/-0.2 mN/mm for heart failure and 1.7+/-0.2 mN/mm for Sham). This difference, but at a higher degree of stretch, was also present in K+-activated vessels. The external application of Ca2+ in K+-depolarized vascular segments in the presence of phentolamine (1 microM) induced an enhanced contractile response in arteries from CHF rats compared with Sham (4.8+/-0.3 mN/mm and 3.6+/-0.6 mN/mm, respectively, P=0.059). In the absence of phentolamine the reverse response was found (4.0+/-0.4 mN/mm and 5.7+/-0.3 mN/mm for CHF vs. Sham respectively, P=0.035). Application of increasing concentrations of K+-solution induced a stronger contractile response in Sham compared with CHF arteries (Sham 4.9+/-0.4 and heart failure 4.0+/-0.3, P=0.04). Microscopic examination of vessels yielded no difference in gross morphology, media thickness or wall to lumen ratio between CHF and Sham arteries. CONCLUSION: The results indicate an attenuation of alpha-adrenoceptors and a difference of Ca2+-mediated vascular contractility in resistance arteries of congestive heart failure rats.

Adrenergic alpha-Antagonists↗

Enhanced endothelin-1-induced contractions in mesenteric arteries from rats with congestive heart failure: role of ET(B) receptors.

Studies of congestive heart failure (CHF) in man and in experimental CHF have demonstrated elevated circulating levels of endothelin (ET). In order to examine whether there are concomitant ET receptor alterations, the vasomotor effects of endothelin-1 (ET-1) and sarafotoxin 6c (S6c) were examined in endothelium-intact and -denuded isolated mesenteric arteries from rats with CHF. CHF was induced by ligation of the left anterior descending coronary artery. Vasomotor responses were studied using small mesenteric arteries (approx. 250 microm in diameter, determined after normalisation). The antagonists IRL2500 and FR139317 were used in order to characterise the ET-1-induced response. In mesenteric arteries with intact endothelium, ET-1-induced contractions were more potent in CHF as compared to sham (pEC(50) 9.6+/-0.2 and 9.1+/-0.1, respectively, P<0.01). In endothelium-denuded arteries, there was no difference in potency of ET-1 between CHF and sham arteries, or in maximum contraction. In the presence of IRL2500, a selective ET(B)-receptor antagonist, ET-1 was more potent in endothelium-denuded arteries of CHF rats, while this difference was not seen in sham arteries. S6c had no consistent contractile or dilatory effect in CHF and sham rats. The results indicate that the enhanced contractile effects of ET-1 noted in CHF might be due to an attenuated endothelial function and that inhibition of smooth muscle cell ET(B) receptors increase the effects of contractile ET(A) receptors in CHF rats.

Animals↗

Endocardial expression and functional characterization of endothelin-1.

Endothelin-1 (ET-1), a 21 amino acid peptide exerts a wide range of biological activities including vasoconstriction, mitogenesis and inotropic effects on the heart. In this study, we examined whether endocardial endothelial cells express ET-1 and evaluated its functional properties. Using immunofluorescence localization method, we demonstrated cytoplasmic staining of ET-1 in the human endocardial endothelial cells from the right atrium and left ventricle. Employing reverse transcriptase polymerase chain reaction (RT-PCR) expression of ET-1 mRNA and its receptors ET(A) and ET(B) mRNAs were found in human myocardial as well as in endocardial endothelial cells. Biological activity of endocardial endothelial cells derived ET-1 was established as the conditioned media obtained from cultured porcine endocardial endothelial cells induced a slowly developing, strong and long-lasting contraction of circular rat aortic segments, with similar characteristics to that obtained with exogenous ET-1. Furthermore, the selective endothelin-A receptor antagonist, FR 139317, blocked the conditioned media induced contractions. Our results suggest that endocardial endothelial cells express and release biologically active ET-1 which could play a pivotal role in the regulation of myocardial contractility as well as a circulatory peptide may further act in other peripheral target organs.

Animals↗

Aspects on the pathophysiology of migraine and cluster headache.

The specific cause of migraine headache remains unknown. Current theories suggest that the initiation of a migraine attack involves a primary CNS dysfunction with subsequent activation of the trigeminovascular system. Studies in patients have revealed a clear association between headache and the release of the neuropeptide calcitonin gene-related peptide, probably from C fibres. In cluster headache and in a case of chronic paroxysmal headache there was in addition release of the parasympathetic neuropeptide vasoactive intestinal peptide, which was associated with headache, nasal congestion and rhinorrhea. Triptan administration, activating the 5-HT(1B/1D) receptors, caused the headache to subside and the neuropeptide release to normalise. These data suggest the involvement of sensory and parasympathetic mechanisms in the pathophysiology of primary headaches.

Autonomic Nervous System↗

Evidence that ET-1, but not ET-3 and S6b, ET(A)-receptor mediated contractions in isolated rat mesenteric arteries are modulated by co-activation of ET(B) receptors.

The effects of agonists with endothelin (ET) ET(A)-receptor activity have been analysed in relation to their interaction with ET(B) receptors in rat mesenteric arteries. ET-1, sarafotoxin 6b (S6b) and ET-3 induced large, slow-onset and sustained contractions whereas S6c induced weak transient contractions. However, following pre-contraction with U46619 and subsequent relaxation with forskolin, the effect of S6c was amplified, indicating a potential for powerful ET(B)-receptor mediated contraction. The selective ET(A)-receptor antagonist, FR139317, produced parallel rightward shifts of ET-1, S6b and ET-3 concentration-effect curves indicating that the contractions were mediated by ET(A) receptors. However, the corresponding FR139317 pK(B) values were significantly different between the agonists. As expected FR139317 had no effect on S6c responses. Pre-treatment with S6c to desensitize ET(B) receptors, increased ET-1 potency and the pK(B) value for FR139317. In contrast, neither the potency of S6b and ET-3 nor the pK(B) values for FR139317 estimated using these agonists were affected by ET(B)-receptor desensitization. Segments pre-contracted with submaximal concentrations of S6b and ET-3, but not ET-1, rapidly relaxed following wash-out or FR139317 administration. The results indicate that the small contractile response to selective ET(B) receptor activation, barely detectable under standard bioassay conditions, is greatly amplified when adenylate cyclase activity is elevated. Moreover, the response to ET(A) receptor activation by ET-1, but not ET-3 and S6b, is significantly modified by co-activation of ET(B) receptors. This interaction has a significant effect on the apparent affinity of ET(A)-receptor selective antagonists when ET-1 is used as agonist and decreases the potency of ET-1.

Adenylyl Cyclases↗

CGRP receptors mediating CGRP-, adrenomedullin- and amylin-induced relaxation in porcine coronary arteries. Characterization with 'Compound 1' (WO98/11128), a non-peptide antagonist.

1. Calcitonin gene-related peptide (CGRP), amylin and adrenomedullin (AM) belong to the same family of peptides. Accumulating evidence indicate that the calcitonin (CT) receptor, the CT receptor-like receptor (CRLR) and receptor-activity-modifying proteins (RAMPs) form the basis of all the receptors in this family of peptides. 2. Using reverse transcriptase - polymerase chain reaction the presence of mRNA sequences encoding the CRLR, RAMP1 and RAMP2 were demonstrated in porcine left anterior descending (LAD) coronary arteries, whereas porcine calcitonin (CT) receptor mRNA was not present. The partial porcine mRNA sequences shared 82 - 92% nucleotide identity with human sequences. 3. The human peptides alphaCGRP, betaCGRP, AM and amylin induced relaxation with pEC(50) values of 8.1, 8.1, 6.7 and 6.1 M respectively. 4. The antagonistic properties of a novel non-peptide CGRP antagonist 'Compound 1' (WO98/11128), betaCGRP(8 - 37) and the proposed AM receptor antagonist AM(22 - 52) were compared to the well-known CGRP(1) receptor antagonist alphaCGRP(8 - 37). 5. The alphaCGRP(8 - 37) and betaCGRP(8 - 37) induced concentration-dependent (10(-7) - 10(-5) M) rightward shift of both the alphaCGRP and betaCGRP concentration-response curves. betaCGRP(8 - 37) (10(-6) M) had the same effect as alphaCGRP(8 - 37) (10(-6) M), but with less potent rightward shift of the concentration-response curves for alphaCGRP, AM and amylin. 6. Preincubation with 'Compound 1' (10(-7) - 10(-5) M) and AM(22 - 52) (10(-6) M) had no significant antagonistic effect. 7. In conclusion, the building blocks forming CGRP and AM receptors were present in the porcine LAD, whereas those of the amylin receptor were not. alphaCGRP, betaCGRP, AM and amylin mediated vasorelaxation via the CGRP receptors. No functional response was detected to adrenomedullin via the adrenomedullin receptor.

Adrenomedullin↗

Vasoactive intestinal peptide has a direct positive inotropic effect on isolated human myocardial trabeculae.

The aim of the present study was to assess the inotropic effects of vasoactive intestinal peptide (VIP) on isolated myocardial trabeculae from the right atrium and the left ventricle of human hearts. Furthermore, using reverse transcriptase-PCR, we wanted to determine the presence of mRNAs encoding the three cloned human VIP receptors, VPAC(1), VPAC(2) and PAC(1). The trabeculae were paced at 1.0 Hz in tissue baths, and changes in isometric contractile force upon exposure to agonist were studied. VIP had a potent positive inotropic effect in some of the atrial and ventricular trabeculae tested. This effect was almost completely blocked by the VIP-receptor antagonist VIP-(6-28). mRNAs encoding the human VPAC(1), VPAC(2) and PAC(1) receptors were detected in human myocardial trabeculae from both the right atrium and the left ventricle. In conclusion, VIP has a direct positive inotropic effect in both the atria and the ventricles of the human heart. The presence of mRNAs for the VPAC(1), VPAC(2) and PAC(1) receptors suggest that VIP may mediate its effect via these receptors.

Adolescent↗

Neuropeptide localization in the "migraine generator" region of the human brainstem.

Evidence from animals and humans suggests that brainstem nuclei such as the raphe nuclei, the locus coeruleus (LC) and the periaqueductal grey matter (PAG), are involved in the pathophysiology of migraine. In order to understand possible neurotransmitters involved we have, by means of indirect immunocytochemistry, analysed these regions for the occurrence and distribution of calcitonin gene-related peptide (CGRP), substance P (SP), pituitary adenylate-cyclase activating peptide (PACAP) and vasoactive intestinal polypeptide (VIP). CGRP-immunoreactive (-ir) cell bodies, but no fibres, were found to occur in high numbers, constituting 80% of all nerve cell bodies in the LC. A smaller number of these nerve cell bodies (40%) in the LC proved to be PACAP-ir. The LC neurones also stored the vesicular monoamine transporter (VMAT)- and the C-terminal flanking peptide of neuropeptide Y (C-PON)-ir, illustrating their adrenergic nature. Double immunostaining revealed that all VMAT-and C-PON-containing neurones, in addition, stored CGRP. Immunoreactive cell bodies were not seen in the nucleus raphe magnus (NRM) or PAG. Numerous SP-ir nerve fibres were observed in the NRM, the LC and the PAG. Few PACAP-ir nerve fibres were detected in the PAG and few VIP-ir nerve fibres were seen in the NRM and the PAG.

Adult↗

Expression of 5-HT1B receptors in human nasal mucosa.

5-HT1B receptors were discovered in human nasal mucosa using immunocytochemistry. Strong immunoreaction was seen around small blood vessels mainly confined to the smooth muscle cell layer. In contrast, no immunoreaction for 5-HT1D was seen. The possibility of local release in connection with specific target receptors suggests a role for 5-HT in the regulation of vascular tone, glandular secretion and epithelial functions and that 5-HT1B receptor agonists may be of clinical importance.

Adult↗

Neuropeptide Y-mediated constriction and dilation in rat middle cerebral arteries.

Neuropeptide Y (NPY) is an important vasoconstrictor in the cerebral circulation. Its constrictor response is because of activation of NPY receptors on the vascular smooth muscle (VSM). Little is known regarding the effects of NPY on the endothelium. In the current study, the authors tested the hypothesis that NPY can either constrict or dilate rat middle cerebral arteries (MCAs). Constriction is elicited by stimulating receptors on the VSM; dilation is elicited by stimulating receptors on the endothelium. Middle cerebral arteries were isolated, cannulated with micropipettes, pressurized to 85 mm Hg, and luminally perfused. The extraluminal application of NPY (mixed agonist), [Leu31, Pro34]-NPY (Y1 agonist), or NPY-[13-36] (Y2 agonist) produced concentration-dependent constrictions. BIBP 3226 (Y1 selective antagonist) significantly attenuated the NPY- and [Leu31, Pro34]-NPY-induced constrictions. The luminal application of NPY, [Leu31, Pro34]-NPY, and NPY-[13-36] produced concentration-dependent dilations of MCAs. The maximum dilation produced by the NPY receptor agonists was approximately 40% of the dilation elicited by the luminal administration of 10(-5) mol/L ATP. Dilations elicited by luminal NPY, [Leu31, Pro34]-NPY, or NPY-[13-36] were abolished by inhibition of nitric oxide synthase with 10(-5) mol/L Nomega-nitro-L-arginine methyl ester (L-NAME) or removal of the endothelium. Dilations produced by luminal NPY or luminal [Leu31, Pro34]-NPY were not affected by BIBP 3226. Stimulation of NPY receptors on vascular smooth muscle constricted MCAs. Stimulation of an NPY receptor other than the Y1 subtype on endothelium dilated the MCAs by releasing nitric oxide.

Animals↗

Sensory nerves in man and their role in primary headaches.

The sensory innervation of intracranial vessels originate in the trigeminal ganglion and comprise the following signal substances; calcitonin gene-related peptide (CGRP), substance P, neurokinin A, pituitary adenylate cyclase activating peptide (PACAP) and nitric oxide (NO). Studies in patients have revealed a clear association between head pain and the release of CGRP. In cluster headache and in a case of chronic paroxysmal headache there is in addition release of vasoactive intestinal peptide (VIP), which was associated with the facial symptoms (nasal congestion, rhinorrhea). In parallel with triptan administration, acting via 5-HT(1B/1D) receptors, head pain subside and neuropeptide release normalise. These data show the involvement of sensory and parasympathetic mechanisms in the pathophysiology of primary headaches.

Animals↗

Calcitonin gene-related peptide (CGRP) and the pathophysiology of headache: therapeutic implications.

Cerebral blood vessels are innervated by sensory nerves that store several neurotransmitters. In primary headaches, there is a clear association between head pain and the release of the neuropeptide calcitonin gene-related peptide (CGRP). Furthermore, when triptan antimigraine agents are administered, headache subsides and the neuropeptide release normalises, in part via a presynaptic effect. The central role of CGRP in primary headaches has led to the search for suitable antagonists of the receptors for this neuropeptide, which it is hoped will have less cardiovascular adverse effects than the triptans. Recently, the initial pharmacological profile of such a group of compounds has been disclosed. These compounds are small molecules with high selectivity for human CGRP receptors. Hypothetically, these agents will be efficacious in the relief of migraine headaches via blockade of the effects of CGRP.

Animals↗

CGRP and adrenomedullin receptor populations in human cerebral arteries: in vitro pharmacological and molecular investigations in different artery sizes.

The aim of the present study was to determine functional and molecular characteristics of receptors for calcitonin gene-related peptide (CGRP) and adrenomedullin in three different diameter groups of lenticulostriate arteries. Furthermore, the presence of perivascular neuronal sources of CGRP was evaluated in these arteries. In the functional studies, in vitro pharmacological experiments demonstrated that both CGRP and adrenomedullin induce alpha-CGRP-(8-37) sensitive vasodilation in artery segments of various diameters. The maximal amounts of vasodilation induced by CGRP and adrenomedullin were not different, whereas the potency of CGRP exceeded that of adrenomedullin by 2 orders of magnitude. Significant negative correlations between artery diameters and maximal responses were demonstrated for CGRP and adrenomedullin. In addition, the potency of both peptides tended to increase in decreasing artery diameter. In the molecular experiments, levels of mRNAs encoding CGRP receptors and receptor subunits were compared using reverse transcriptase polymerase chain reactions (RT-PCR). The larger the artery, the more mRNA encoding receptor activity-modifying proteins 1 and 2 (RAMP1 and RAMP2) was detected relative to the amount of mRNA encoding the calcitonin receptor-like receptor. By immunohistochemistry, perivascular CGRP containing nerve fibres were demonstrated in all the investigated artery sizes. In conclusion, both CGRP and adrenomedullin induced vasodilation via CGRP receptors in human lenticulostriate artery of various diameter. The artery responsiveness to the CGRP receptor agonists increased with smaller artery diameter, whereas the receptor-phenotype determining mRNA ratios tended to decrease. No evidence for CGRP and adrenomedullin receptor heterogeneity was present in lenticulostriate arteries of different diameters.

Adrenomedullin↗

Positive inotropy mediated via CGRP receptors in isolated human myocardial trabeculae.

Isometric contractile force were studied on isolated human myocardial trabeculae that were paced at 1.0 Hz in tissue baths. Alpha calcitonin gene-related peptide (alpha-CGRP) had a potent positive inotropic effect in most trabeculae from both the right atrium and left ventricle, and this effect was partially antagonized by the CGRP(1) receptor antagonist alpha-CGRP-(8-37) (10(-6) M). Amylin and the CGRP(2) receptor agonist [Cys(acetylmethoxy)(2, 7)]CGRP had a positive inotropic effect in some trabeculae, whereas adrenomedullin had no inotropic effect. Using reverse transcriptase-polymerase chain reaction (PCR) mRNAs encoding the human calcitonin receptor-like receptor and the receptor associated modifying proteins (RAMPs) RAMP1, RAMP2, and RAMP3 were detected in human myocardial trabeculae from both the right atrium and left ventricle. In conclusion, functional CGRP(1) and CGRP(2) receptors may mediate a positive inotropic effect at both the atrial and ventricular level of the human heart. mRNAs for calcitonin receptor-like receptor and specific RAMPs further support the presence of CGRP receptors.

Adrenomedullin↗

Increased sensitivity to ET-1 in rat cerebral arteries following organ culture.

Endothelin-1 (ET-1) is recognized as being involved in the pathophysiology of cerebrovascular diseases. Using organ culture as a model for possible pathological changes we studied changes in ET(A) and ETB receptor function using a sensitive in vitro method. We observed an up-regulation of the ET(B) receptor and an amazingly increased sensitivity to ET-1 by 3 log units in pEC50; pEC50(fresh) was 8.7 +/- 0.1, and pEC50(cultured) was 11.7 +/- 0.3. pA2 for FR139317 in the fresh vessel was 7.0 +/- 0.2 whereas it could not be obtained for the cultured vessel, indicating a possible cross-talk between the ET(A) and ET(B) receptors. The increased sensitivity to ET-1 could also take place during cerebrovascular disease such as stroke or haemorrhage rendering the vessels considerably more sensitive to ET-1.

Animals↗

P2X receptors counteract the vasodilatory effects of endothelium derived hyperpolarising factor.

Dilatory responses of extracellular nucleotides were examined in the precontracted isolated rat mesenteric artery. Dilatation mediated by endothelium-derived hyperpolarising factor (EDHF) was studied in the presence of Nomega-nitro-L-arginine (L-NOARG) and indomethacin, and was most potently induced by the selective P2Y(1) receptor agonist adenosine 5'-O-thiodiphosphate (ADPbetaS), while 2-methylthioadenosine triphosphate (2-MeSATP) and adenosine triphosphate (ATP) were almost inactive. However, after P2X receptor desensitisation (with alphabeta-methylene-adenosine triphosphate, alphabeta-MeATP), 2-MeSATP and ATP potently stimulated EDHF-mediated dilatation. This can be explained by simultaneous activation of endothelial P2Y receptors that release EDHF, and depolarising P2X receptors on smooth muscle cells. Uridine triphosphate (UTP) also induced potent dilatation, suggesting EDHF release via P2Y(2)/P2Y(4) receptors. Uridine diphosphate (UDP) had only minor dilatory effects, and when pretreated with hexokinase it was almost inactive, suggesting a minor role for P2Y(6) receptors. The nitric oxide (NO) mediated dilatation was studied in the presence of charybdotoxin, apamin and indomethacin. ADPbetaS, 2-MeSATP, ATP and UTP were all potent relaxant agonists suggesting NO release via P2Y(1) and P2Y(2)/P2Y(4) receptors, while UDP was much less potent and efficacious. P2X receptor desensitisation had only minor effect on the NO-mediated dilatations. In conclusion, both EDHF and NO-mediated dilatation can be induced by activation of P2Y(1) and P2Y(2)/P2Y(4) receptors. P2X receptor stimulation of smooth muscle cells selectively counteracts the dilatory effect of EDHF.

Animals↗