Inhibition Of Calcitonin Gene-related Peptide Release Research Articles

Pharmacological Profile of the Purinergic P2Y Receptors That Modulate, in Response to ADPβS, the Vasodepressor Sensory CGRPergic Outflow in Pithed Rats.

Calcitonin gene-related peptide (CGRP), an endogenous neuropeptide released from perivascular sensory nerves, exerts a powerful vasodilatation. Interestingly, adenosine triphosphate (ATP) stimulates the release of CGRP by activation of prejunctional P2X2/3 receptors, and adenosine 5'-O-2-thiodiphosphate (ADPβS), a stable adenosine diphosphate (ADP) analogue, produces vasodilator/vasodepressor responses by endothelial P2Y1 receptors. Since the role of ADP in the prejunctional modulation of the vasodepressor sensory CGRPergic drive and the receptors involved remain unknown, this study investigated whether ADPβS inhibits this CGRPergic drive. Accordingly, 132 male Wistar rats were pithed and subsequently divided into two sets. In set 1, ADPβS (5.6 and 10 µg/kg·min) inhibited the vasodepressor CGRPergic responses by electrical stimulation of the spinal T9-T12 segment. This inhibition by ADPβS (5.6 µg/kg·min) was reverted after i.v. administration of the purinergic antagonists MRS2500 (300 µg/kg; P2Y1) or MRS2211 (3000 µg/kg; P2Y13), but not by PSB0739 (300 µg/kg; P2Y12), MRS2211 (1000 µg/kg; P2Y13) or the KATP blocker glibenclamide (20 mg/kg). In set 2, ADPβS (5.6 µg/kg·min) failed to modify the vasodepressor responses to exogenous α-CGRP. These results suggest that ADPβS inhibits CGRP release in perivascular sensory nerves. This inhibition, apparently unrelated to activation of ATP-sensitive K+ channels, involves P2Y1 and probably P2Y13, but not P2Y12 receptors.

Recent advances in targeting calcitonin gene-related peptide for the treatment of menstrual migraine: A narrative review.

Menstrual migraine (MM) has a longer duration and higher drug resistance than non-perimenstrual migraine. Calcitonin gene-related peptide (CGRP) and CGRP receptors are expressed in the peripheral and central nervous systems throughout the trigeminovascular system. The CGRP/CGRP receptor axis plays an important role in sensory physiology and pharmacology. CGRP receptor antagonists and anti-CGRP monoclonal antibodies (mAbs) have shown consistent efficacy and tolerability in the prevention of chronic or episodic migraine and are now approved for clinical use. However, few studies have reported the use of these drugs in MM, and no specific treatment for MM has been approved. This review aimed to shed light on the recent advances in targeting calcitonin gene-related peptides for the treatment of menstrual migraines in PubMed. In this review, we first discuss the axis of the CGRP/CGRP receptor. We then discuss the role of CGRP receptor antagonists and anti-CGRP mAbs in MM treatment. Finally, we discuss the role of the combination of anti-CGRP mAbs and CGRP receptor antagonists in migraine treatment and the drugs that inhibit CGRP release. Altogether, the anti-CGRP mAbs or CGRP receptor antagonists showed good efficacy and safety in the treatment of MM.

Effect of Ultrasound Guided Bilateral Greater Occipital Nerve Block on Serum Calcitonin Gene Related Peptide (CGRP) in Chronic Migraine

Background: The trigeminal ganglion plays a key role in primary headache pathophysiology. Calcitonin gene-related peptide (CGRP) and CGRP receptors are expressed in trigeminal neurons that form C-fibers and A-fibers, respectively. In migraine attacks, there is release of CGRP into the cranial venous outflow, in refractory headache to conventional pharmacologic management, minimally invasive techniques such as greater occipital nerve block (GONB) are feasible for pain relief, and help to decrease the frequency of the attacks, Studies on the ultrasound (US) guided GON injection technique have emphasized that this technique has a higher success rate and should allow for a more precise block of the nerve. Our study will be concerned by correlation of CGRP level as a biomarker for effectiveness and responders of us guided GON block in chronic migraine (CM). Methods: twenty patients diagnosed with chronic migraine were recruited in this study. All participants underwent ultrasound-guided bilat. GONB by 40 mg triamcinolone and 1 cc leidocaine using a portable ultrasound system with a 7 – 13 MHz multifrequency transducer, blood samples were collected from antecubital vein immediately before and three to five weeks after injection clinical response was evaluated using headache diaries Results: CGRP levels after ultrasound guided GONB (median, 40 pg/mL; range, 25-60) were significantly lower as compared with CGRP levels obtained before GONB (median, 145 pg/mL; range, 60-380; P =0.001). Pretreatment CGRP levels in non-responders (310 pg/mL) were significantly higher than those seen in responders being in poor responders less than 50% improvement (135 pg/ml) and good responders (140 pg/mL; P = 0.003). One month after treatment. A number of demographic factors, clinical features, and comorbidities were not different in responders as compared with those of nonresponders. Conclusion: These results suggests that interictal CGRP levels can be of help in predicting the response to GONB and suggest that the mechanism of action of GONB in CM is the reversal of sensitization as a result of the inhibition of CGRP release still more studies needed to highlight CGRP role with GONB

Gepants and Ditans

The calcitonin gene-related peptide (CGRP) has been shown to play a major role in the pathophysiology of migraine in recent years. Studies have suggested that blocking CGRP signaling is an effective preventive and therapeutic strategy in patients with migraine. Triptans, considered the mainstay of antimigraine treatment cause vasoconstriction; however, gepants and ditans (two novel classes of therapeutic agents) inhibit CGRP release but do not show a vasoconstrictor effect. Both these drugs are awaiting clinical approval in Japan as antimigraine medications that can be administered to patients with cardiovascular risk factors and to those with triptan-refractory migraine.

Lasmiditan inhibits calcitonin gene-related peptide release in the rodent trigeminovascular system.

Migraine headache pathophysiology involves trigeminovascular system activation, calcitonin gene-related peptide (CGRP) release, and dysfunctional nociceptive transmission. Triptans are 5-HT1B/1D/(1F) receptor agonists that prejunctionally inhibit trigeminal CGRP release, but their vasoconstrictor properties limit their use in migraine patients with cardiovascular disease. By contrast, lasmiditan is a novel antimigraine and selective 5-HT1F receptor agonist devoid of vasoconstrictor properties. On this basis, this study has investigated the modulation of trigeminal CGRP release by lasmiditan. For this purpose, we have comparatively analysed the inhibition of several components of the trigeminovascular system induced by lasmiditan and sumatriptan through: ex vivo KCl-induced CGRP release from isolated dura mater, trigeminal ganglion, and trigeminal nucleus caudalis of mice; and in vivo dural vasodilation in the rat closed-cranial window model induced by endogenous (electrical stimulation and capsaicin) and exogenous CGRP. The ex vivo release of CGRP was similarly inhibited by sumatriptan and lasmiditan in all trigeminovascular system components. In vivo, intravenous (i.v.) lasmiditan or higher doses of sumatriptan significantly attenuated the vasodilatory responses to endogenous CGRP release, but not exogenous CGRP effects. These data suggest that lasmiditan prejunctionally inhibits CGRP release in peripheral and central trigeminal nerve terminals. Because lasmiditan is a lipophilic drug that crosses the blood-brain barrier, additional central sites of action remain to be determined.

Perampanel inhibits calcitonin gene-related peptide release from rat brainstem in vitro

BackgroundPerampanel is a novel antiepileptic drug acting via non-competitive antagonism on glutamatergic AMPA receptors, and the subsequent inhibition of ion calcium influx. Since it was recently postulated that the antagonists of glutamate receptors might play a role in the treatment of migraine, in this study we investigated the putative anti-migraine activity of perampanel in an in vitro animal model involving the static incubation of rat brainstem explants and the subsequent measurement of immune-reactive calcitonin gene-related peptide released into the incubation medium.MethodsAcute rat brainstem explants were incubated in plain medium or in medium containing graded concentrations of perampanel. The release into the medium was assessed by radioimmunoassay either under baseline conditions or after stimulation by such secretagogues as high K+ concentrations, veratridine or capsaicin.ResultsWe found that: 1) under baseline conditions perampanel, given in the range 0.01–100 μM, inhibited in a concentration-dependent manner calcitonin gene-related peptide’s release compared to controls; the decrease was statistically significant as from 10 μM; 2) a significant and consistent increase in calcitonin gene-related peptide’s secretion was induced by all depolarizing stimuli after 1 h of incubation; 3) under these conditions, calcitonin gene-related peptide’s release stimulated by 56 mM KCl was significantly reduced by perampanel from 0.1 μM onward, whereas secretion stimulated by veratridine was significantly reduced as from 1 μM; 4) on the contrary, perampanel had no effect on capsaicin-induced calcitonin gene-related peptide’s release up to 100 μM.ConclusionsHere we provided preliminary in vitro evidence suggesting that perampanel might control pain transmission under conditions of activated trigeminal system, in a preclinical model mimicking the pathophysiology of human migraine.

Lacosamide inhibits calcitonin gene-related peptide production and release at trigeminal level in the rat.

Several classes of drugs are effective in prevention and treatment of migraine, although they may differ among each other in their mode of action and in indications. One such class is represented by antiepileptics. Lacosamide is an approved antiepileptic drug that also shows antinociceptive activity in animal models, including analgesic efficacy in central and trigeminal pain. Calcitonin gene-related peptide (CGRP) is considered the main neuro-mediator of trigeminal signalling, playing an essential role in headache, migraine in particular. Here, we investigated the effects of lacosamide on CGRP signalling in both invitro and exvivo/vitro models in the rat. We assessed: (1) CGRP released from brainstem explants at baseline or after pharmacological challenges; and (2) CGRP levels in brain areas after invivo treatments with test drugs. We found that: (1) lacosamide inhibits CGRP release from brainstem explants under basal conditions as well as after stimulation by 56mM KCl, 10μM veratridine or 1μM capsaicin; and (2) the i.p. administration of nitroglycerine produces an increase in CGRP levels in the brainstem and trigeminal ganglia, which is inhibited by a pre-treatment with lacosamide. These findings provide preliminary evidence suggesting that lacosamide is able to control pain transmission under conditions affecting the trigeminal system, such as migraine.

The analgesic agent tapentadol inhibits calcitonin gene-related peptide release from isolated rat brainstem via a serotonergic mechanism

AimsIn this study we tested the hypothesis that tapentadol inhibits GGRP release from the rat brainstem through a mechanism mediated by the inhibition of NA reuptake; as a second alternative hypothesis, we investigated whether tapentadol inhibits GGRP release via the inhibition of 5-HT reuptake. MethodsRat brainstems were explanted and incubated in short-term experiments. CGRP released in the incubation medium was taken as a marker of CGRP release from the central terminals of trigeminal neurons within the brainstem. CGRP levels were measured by radioimmunoassay under basal conditions or in the presence of tapentadol; NA, 5-HT, clonidine, yohimbine and ondansetron were used as pharmacological tools to investigate the action mechanism of tapentadol. ResultsThe α2-antagonist yohimbine failed to counteract the effects of tapentadol. Moreover, neither NA nor the α2-agonist clonidine per se inhibited K+−stimulated CGRP release, thereby indicating that the effects of tapentadol are nor mediated through the block of NA reuptake. Further experiments showed that 5-HT and tramadol, which inhibits both NA and 5-HT reuptake, significantly reduced K+-stimulated CGRP release. Moreover, the 5-HT3 antagonist ondansetron was able to counteract the effects of tapentadol in this system. SignificanceThis study provided pharmacological evidence that tapentadol inhibits stimulated CGRP release from the rat brainstem in vitro through a mechanism involving an increase in 5-HT levels in the system and the subsequent activation of 5-HT3 receptors.

Tapentadol inhibits calcitonin gene-related peptide release from rat brainstem in vitro

We have previously developed an in vitro model of rat brainstem explants. The latter release sizable amounts of calcitonin gene-related peptide (CGRP); basal release can be stimulated by such secretagogues as high KCl concentrations, veratridine or capsaicine. In this paradigm we investigated the activity of the analgesic agent tapentadol; the effects of tapentadol were compared to those of a classical opioid receptor agonist, morphine, and the selective noradrenaline reuptake inhibitor reboxetine. Morphine inhibited basal CGRP release, with statistical significance from 1nM onward and maximal (−44%) inhibition at 100μM. Morphine also inhibited K+-stimulated peptide release, with a significant effect from 1μM and maximal (−39%) decrease at 100μM, but failed to inhibit release stimulated by 10μM capsaicin. At variance, reboxetine had no effect on baseline CGRP outflow, but was able to inhibit both K+-stimulated [significant inhibition from 1μM onward and maximal (−37%) decrease at 100μM], and capsaicin-stimulated release [significant effect from 1μM and maximal (−31%) decrease at 100μM]. Likewise, tapentadol had no effect on baseline CGRP release up to 100μM, but decreased secretion stimulated by 56mM KCl or capsaicin, with significant effects from 0.1 and 1μM respectively; maximal inhibition over 56mM KCl and capsaicin stimuli was −29% and −31%, respectively. Naloxone antagonized the effect of morphine, but not those of reboxetine and tapentadol, on K+-stimulated CGRP secretion. In conclusion the present study provides consistent pharmacological evidence that tapentadol acts as a noradrenaline reuptake inhibitor agent in this experimental model.

Selective Cleavage of SNAREs in Sensory Neurons Unveils Protein Complexes Mediating Peptide Exocytosis Triggered by Different Stimuli

Oligomerisation of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes is required for synaptic vesicle fusion and neurotransmitter release. How these regulate the release of pain peptides elicited by different stimuli from sensory neurons has not been established. Herein, K(+) depolarization was found to induce multiple sodium dodecyl sulfate (SDS)-resistant SNARE complexes in sensory neurons exposed to botulinum neurotoxins (BoNTs), with molecular weights ranging from 104-288 k (large) to 38-104 k (small). Isoform 1 of vesicle-associated membrane protein 1 (VAMP 1) assembled into stable complexes upon depolarisation and was required for the participation of intact synaptosome-associated protein of relative molecular mass 25 k (SNAP-25) or BoNT/A-truncated form (SNAP-25A) in the large functional and small inactive SDS-resistant SNARE complexes. Cleaving VAMP 1 decreased SNAP-25A in the functional complexes to a much greater extent than the remaining intact SNAP-25. Syntaxin 1 proved essential for the incorporation of intact and SNAP-25A into the large complexes. Truncation of syntaxin 1 by BoNT/C1 caused /A- and/or /C1-truncated SNAP-25 to appear in non-functional complexes and blocked the release of calcitonin gene-related peptide (CGRP) elicited by capsaicin, ionomycin, thapsigargin or K(+) depolarization. Only the latter two were susceptible to /A. Inhibition of CGRP release by BoNT/A was reversed by capsaicin and/or ionomycin, an effect overcome by BoNT/C1. Unlike BoNT/B, BoNT/D cleaved VAMP 1 in addition to 2 and 3 in rat sensory neurons and blocked both CGRP and substance P release. Thus, unlike SNAP-25, syntaxin 1 and VAMP 1 are more suitable targets to abolish functional SNARE complexes and pain peptide release evoked by any stimuli.

Parthenolide inhibits nociception and neurogenic vasodilatation in the trigeminovascular system by targeting the TRPA1 channel

Although feverfew has been used for centuries to treat pain and headaches and is recommended for migraine treatment, the mechanism for its protective action remains unknown. Migraine is triggered by calcitonin gene-related peptide (CGRP) release from trigeminal neurons. Peptidergic sensory neurons express a series of transient receptor potential (TRP) channels, including the ankyrin 1 (TRPA1) channel. Recent findings have identified agents either inhaled from the environment or produced endogenously that are known to trigger migraine or cluster headache attacks, such as TRPA1 simulants. A major constituent of feverfew, parthenolide, may interact with TRPA1 nucleophilic sites, suggesting that feverfew’s antimigraine effect derives from its ability to target TRPA1. We found that parthenolide stimulates recombinant (transfected cells) or natively expressed (rat/mouse trigeminal neurons) TRPA1, where it, however, behaves as a partial agonist. Furthermore, in rodents, after initial stimulation, parthenolide desensitizes the TRPA1 channel and renders peptidergic TRPA1-expressing nerve terminals unresponsive to any stimulus. This effect of parthenolide abrogates nociceptive responses evoked by stimulation of peripheral trigeminal endings. TRPA1 targeting and neuronal desensitization by parthenolide inhibits CGRP release from trigeminal neurons and CGRP-mediated meningeal vasodilatation, evoked by either TRPA1 agonists or other unspecific stimuli. TRPA1 partial agonism, together with desensitization and nociceptor defunctionalization, ultimately resulting in inhibition of CGRP release within the trigeminovascular system, may contribute to the antimigraine effect of parthenolide.

NXN-188, a selective nNOS inhibitor and a 5-HT1B/1D receptor agonist, inhibits CGRP release in preclinical migraine models

NXN-188 is a combined neuronal nitric oxide synthase (nNOS) inhibitor and 5-hydroxytryptamine 1B/1D (5-HT1B/1D) receptor agonist. Using preclinical models, we evaluated whether these two unique therapeutic principles have a synergistic effect in attenuating stimulated calcitonin gene-related peptide (CGRP) release, a marker of trigeminal activation. We examined the effect of NXN-188 on: (1) KCl-, capsaicin- and resiniferatoxin (RTX)-induced immunoreactive CGRP (iCGRP) release from isolated preparation of rat dura mater, trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC); and (2) capsaicin- and electrical stimulation (ES)-induced middle meningeal artery (MMA) dilation in a rat closed-cranial window. NXN-188 inhibited: (1) KCl-stimulated iCGRP release from dura mater (% decrease mean ± SEM, lowest effective concentration) (35 ± 6%, 30 µM), TG (24 ± 11%, 10 µM) and TNC (40 ± 8%, 10 µM); (2) capsaicin- and RTX-induced iCGRP release from dura mater; and (3) capsaicin- and ES-induced increase in dural artery diameter (32 ± 5%, 3 mg kg(-1) intravenous (i.v.) and 36 ± 1%, 10 mg kg(-1) i.v.). NXN-188 inhibits CGRP release from migraine-relevant cephalic tissues. Its effect is most likely mediated via a combination of nNOS-inhibition and 5-HT1B/1D receptor agonism in dura mater while the mechanisms of action for inhibition of CGRP release from TG and TNC have to be investigated further.

Modulation of CGRP-Induced Light Aversion in Wild-Type Mice by a 5-HT1B/DAgonist

The neuropeptide calcitonin gene-related peptide (CGRP) plays a critical role in the pathophysiology of migraine. We have focused on the role of CGRP in photophobia, which is a common migraine symptom. We previously used an operant-based assay to show that CGRP-sensitized transgenic (nestin/hRAMP1), but not control, mice exhibited light aversion in response to an intracerebroventricular CGRP injection. A key question was whether the transgenic phenotype was due to overexpression of the CGRP receptor at endogenous or novel expression sites. We reasoned that if endogenous receptor sites were sufficient for light-aversive behavior, then wild-type mice should also show the phenotype when given a sufficiently strong stimulus. In this study, we report that mice with normal levels of endogenous CGRP receptors demonstrate light avoidance following CGRP administration. This phenotype required the combination of two factors: higher light intensity and habituation to the testing chamber. Control tests confirmed that light aversion was dependent on coincident exposure to CGRP and light and cannot be fully explained by increased anxiety. Furthermore, CGRP reduced locomotion only in the dark, not in the light. Coadministration of rizatriptan, a 5-HT(1B/D) agonist anti-migraine drug, attenuated the effects of exogenous CGRP on light aversion and motility. This suggests that triptans can act by mechanisms that are distinct from inhibition of CGRP release. Thus, we demonstrate that activation of endogenous CGRP receptors is sufficient to elicit light aversion in mice, which can be modulated by a drug commonly used to treat migraine.

Intracisternal Injection of Inflammatory Soup Activates the Trigeminal Nerve System

The release of calcitonin gene-related peptide (CGRP) and sensitization of the trigeminal nerve system are important elements in migraine pathophysiology. Sensitization can be induced by topical meningeal administration of inflammatory soup (IS). CGRP release is a marker of trigeminal nerve activation. We examined the effect of intracisternal IS administration on CGRP release in rat jugular vein blood at baseline, 2 and 15 min after the beginning of IS infusion. IS administration caused a significant increase of CGRP levels after 2 and 15 min compared with baseline. Daily oral treatment with topiramate for 4 and 8 weeks led to a dose- and time-dependent reduction of IS-induced CGRP release. Sumatriptan also attenuated stimulated neuropeptide release. These results indicate that intracisternal IS administration leads to activation of the trigeminal system. The inhibition of CGRP release by topiramate offers a possible mechanism that may in part account for the preventative antimigraine activity of this drug.

Protein Kinase C Mediates the Synergistic Interaction Between Agonists Acting at α2-Adrenergic and Delta-Opioid Receptors in Spinal Cord

Coactivation of spinal alpha(2)-adrenergic receptors (ARs) and opioid receptors produces antinociceptive synergy. Antinociceptive synergy between intrathecally administered alpha(2)AR and opioid agonists is well documented, but the mechanism underlying this synergy remains unclear. The delta-opioid receptor (DOP) and the alpha(2A)ARs are coexpressed on the terminals of primary afferent fibers in the spinal cord where they may mediate this phenomenon. We evaluated the ability of the DOP-selective agonist deltorphin II (DELT), the alpha(2)AR agonist clonidine (CLON) or their combination to inhibit calcitonin gene-related peptide (CGRP) release from spinal cord slices. We then examined the possible underlying signaling mechanisms involved through coadministration of inhibitors of phospholipase C (PLC), protein kinase C (PKC) or protein kinase A (PKA). Potassium-evoked depolarization of spinal cord slices caused concentration-dependent release of CGRP. Coadministration of DELT and CLON inhibited the release of CGRP in a synergistic manner as confirmed statistically by isobolograpic analysis. Synergy was dependent on the activation of PLC and PKC, but not PKA, whereas the effect of agonist administration alone was only dependent on PLC. The importance of these findings was confirmed in vivo, using a thermal nociceptive test, demonstrating the PKC dependence of CLON-DELT antinociceptive synergy in mice. That inhibition of CGRP release by the combination was maintained in the presence of tetrodotoxin in spinal cord slices suggests that synergy does not rely on interneuronal signaling and may occur within single subcellular compartments. The present study reveals a novel signaling pathway underlying the synergistic analgesic interaction between DOP and alpha(2)AR agonists in the spinal cord.

Shock wave induced kidney injury promotes calcium oxalate deposition

622Urological Surveyare phospholipid bilayered vesicles, and evaluated the urodynamic and immunohistochemical effect on acetic acid induced bladder hyperactivity in rats. Materials and Methods: Liposomes (1 ml), botulinum toxin A (20 U/1 ml saline) or botulinum toxin A en-capsulated in liposomes (lipotoxin, that is 20 U botulinum toxin A plus 1 ml liposomes) was administered in the bladder and retained for 1 hour on day 1 after baseline cystometrogram. Continuous cystometrogram was performed on day 1 by filling the bladder with saline and on day 8 by filling the bladder with saline, followed by 0.3% acetic acid. The bladder was then harvested. Cystometrogram parameters, histology, SNAP25 and calcitonin gene-related peptide expression were measured by Western blotting or immunostaining. Results: The intercontraction interval was decreased 57.2% and 56.0% after intravesical acetic acid instillation in liposome and botulinum toxin A pretreated rats, respectively. However, rats that received lipotoxin showed a significantly decreased intercontraction interval response (21.1% decrease) to acetic acid instillation but without compromised voiding function. Also, lipotoxin pretreated rats had a better decrease in the inflammatory reac-tion and SNAP-25 expression, and increase in calcitonin gene-related peptide immunoreactivity than those in liposome or botulinum toxin A pretreated rats. Conclusions: Intravesical lipotoxin administration cleaved SNAP-25, inhibited calcitonin gene-related peptide release from afferent nerve terminals and blocked the acetic acid induced hyperactive bladder. These results support liposomes as an efficient vehicle for delivering botulinum toxin A without injection.

Urodynamic and Immunohistochemical Evaluation of Intravesical Botulinum Toxin A Delivery Using Liposomes

Botulinum toxin A (Allergan, Irvine, California) is a high molecular weight neurotoxin used to treat hypersensitive bladder by direct injection to pass the urothelial barrier. We investigated the feasibility of intravesical botulinum toxin A delivery using liposomes (Lipella Pharmaceuticals, Pittsburgh, Pennsylvania), which are phospholipid bilayered vesicles, and evaluated the urodynamic and immunohistochemical effect on acetic acid induced bladder hyperactivity in rats. Liposomes (1 ml), botulinum toxin A (20 U/1 ml saline) or botulinum toxin A encapsulated in liposomes (lipotoxin, that is 20 U botulinum toxin A plus 1 ml liposomes) was administered in the bladder and retained for 1 hour on day 1 after baseline cystometrogram. Continuous cystometrogram was performed on day 1 by filling the bladder with saline and on day 8 by filling the bladder with saline, followed by 0.3% acetic acid. The bladder was then harvested. Cystometrogram parameters, histology, SNAP25 and calcitonin gene-related peptide expression were measured by Western blotting or immunostaining. The intercontraction interval was decreased 57.2% and 56.0% after intravesical acetic acid instillation in liposome and botulinum toxin A pretreated rats, respectively. However, rats that received lipotoxin showed a significantly decreased intercontraction interval response (21.1% decrease) to acetic acid instillation but without compromised voiding function. Also, lipotoxin pretreated rats had a better decrease in the inflammatory reaction and SNAP-25 expression, and increase in calcitonin gene-related peptide immunoreactivity than those in liposome or botulinum toxin A pretreated rats. Intravesical lipotoxin administration cleaved SNAP-25, inhibited calcitonin gene-related peptide release from afferent nerve terminals and blocked the acetic acid induced hyperactive bladder. These results support liposomes as an efficient vehicle for delivering botulinum toxin A without injection.

Spinal sumatriptan inhibits capsaicin-induced canine external carotid vasodilatation via 5-HT 1B rather than 5-HT 1D receptors

Migraine is a neurovascular disorder associated with trigeminal activation, vasodilatation and trigeminal release of calcitonin gene-related peptide (CGRP). The antimigraine properties of triptans may be due to: i) vasoconstriction of the carotid arterial bed via 5-HT 1B receptors; and ii) inhibition of CGRP release from trigeminal nerves, via 5-HT 1B/1D receptors. This study investigated the effects of intrathecally administered sumatriptan (a 5-HT 1B/1D receptor agonist) and PNU-142633 (a 5-HT 1D receptor agonist) on the canine external carotid vasodilator responses to capsaicin, α-CGRP and acetylcholine. For this purpose, 42 mongrel dogs were anaesthetised with sodium pentobarbitone and, subsequently, vagosympathectomized. The animals were prepared to measure arterial blood pressure, heart rate and external carotid blood flow; the thyroid artery was cannulated for infusion of agonists. 1-min intracarotid (i.c.) continuous infusions of capsaicin, α-CGRP and acetylcholine produced dose-dependent increases in external carotid blood flow without affecting arterial blood pressure or heart rate. These vasodilator responses remained unaffected after intrathecal (i.t.) administration of physiological saline (0.5 ml) or PNU-142633 (300–1000 μg); in contrast, i.t. sumatriptan (300–1000 μg) significantly inhibited the vasodilator responses to capsaicin, but not those to α-CGRP or acetylcholine. Furthermore, i.t. administration of SB224289 (a 5-HT 1B receptor antagonist), but not of BRL15572 (a 5-HT 1D receptor antagonist), abolished the above inhibition by sumatriptan. These results suggest that sumatriptan-induced inhibition of the external carotid vasodilatation to capsaicin involves a central mechanism mainly mediated by 5-HT 1B receptors.

The Future of Migraine: Beyond Just Another Pill

The Future of Migraine: Beyond Just Another Pill

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Interstitial cystitis (IC) is a disease of mystery. This disease causes increased bladder sensitivity, decreased bladder capacity, and a painful bladder, whether empty or full. Recently, most physicians have concluded that IC is an inflammatory disease that can progress if not treated. However, the effects of treatment aiming at protection of the urothelium have usually been limited. 1 Nickel J.C. Barkin J. Forrest J. et al. Randomized, double-blind, dose-ranging study of pentosan polysulfate sodium for interstitial cystitis. Urology. 2005; 65: 654-658 Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar Botulinum toxin type A (BTX-A) injection provides a novel treatment of IC, decreasing bladder sensitivity by reducing the sensory receptors, such as P2X3 and transient receptor potential vanilloid 1, 2 Apostolidis A. Papat R. Yiangou Y. et al. Decreased sensory receptors P2X3 and TRPV1 in suburothelial nerve fibers following intradetrusor injection of botulinum A toxin for human detrusor overactivity. J Urol. 2005; 173: 977-983 Abstract Full Text Full Text PDF Scopus (359) Google Scholar increasing bladder capacity by paralyzing the detrusor, 3 Kuo H.C. Urodynamic evidence of effectiveness of botulinum A toxin injection in treatment of detrusor overactivity refractory to anticholinergic agents. Urology. 2004; 63: 868-872 Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar and decreasing bladder pain by suppressing the release of calcitonin gene-related peptide and other neuropeptides. 4 Rapp D.E. Turk K.W. Bales G.T. et al. Botulinum toxin type A inhibits calcitonin gene-related peptide release from isolated rat bladder. J Urol. 2006; 175: 1138-1142 Abstract Full Text Full Text PDF PubMed Scopus (143) Google Scholar The actual mechanism of effective BTX-A treatment has not been elucidated. It is possibly through inhibition of the inflammatory process. This letter-to-editor points out the underlying molecular mechanism of BTX-A affects on the proinflammatory pathway, which further modulates the secretion of nerve growth factor from the bladder wall. By inhibiting the inflammatory process in the suburothelium or urothelium, BTX-A not only might decrease the apoptosis of urothelial cells, but also could reestablish the integrity of the injured urothelium. However, because the inflammatory process in IC might involve the corresponding spinal cords, 5 Cui M. Aoki K.R. Botulinum toxin type A (BTX-A) reduces inflammatory pain in the rat formalin model. Cephalalgia. 2000; 20: 414-418 Crossref Google Scholar the therapeutic result of BTX-A on IC through detrusor injection cannot last for long. Repeated BTX-A injections might provide long-term desensitization to the inflammation of the central nervous system in IC and a better treatment outcome. Intravesical Botulinum Toxin A Injections Plus Hydrodistension Can Reduce Nerve Growth Factor Production and Control Bladder Pain in Interstitial Cystitis: A Molecular MechanismUrologyVol. 72Issue 2PreviewI read with great interest the article by Liu and colleagues.1 This work shows that botulinum toxin markedly reduces nerve growth factor (NGF) compared with a placebo. I would like to complete the discussion of Liu and coworkers1 by suggesting a major route through which botulinum toxin could reduce NGF. Full-Text PDF