Dihydroergotamine protects against ischemic stroke by modulating microglial/macrophage polarization and inhibiting inflammation in mice

OBJECTIVES

The search for drugs that can protect the brain tissue and reduce nerve damage in acute ischemic stroke has emerged as a research hotspot. We investigated the potential protective effects and mechanisms of action of dihydroergotamine against ischemic stroke.

METHODS

C57BL/6 mice were subjected to middle cerebral artery occlusion (MCAO), and dihydroergotamine at a dose of 10 mg/kg/day was intraperitoneally injected for 14 days. Adhesive removal and beam walking tests were conducted 1, 3, 5, 7, 10, and 14 days after MCAO surgery. Thereafter, the mechanism by which dihydroergotamine regulates microglia/macrophage polarization and inflammation and imparts ischemic stroke protection was studied using enzyme-linked immunosorbent assay, immunofluorescence staining, and western blotting.

RESULTS

From the perspective of a drug repurposing strategy, dihydroergotamine was found to inhibit oxygen-glucose deprivation damage to neurons, significantly improve cell survival rate, and likely exert a protective effect on ischemic brain injury. Dihydroergotamine significantly improved neural function scores and survival rates and reduced brain injury severity in mice. Furthermore, dihydroergotamine manifests its protective effect on ischemic brain injury by reducing the expression of TNF-α and IL-1β in mouse ischemic brain tissue, inhibiting the polarization of microglia/macrophage toward the M1 phenotype and promoting polarization toward the M2 phenotype.

CONCLUSION

This study is the first to demonstrate the protective effect of dihydroergotamine, a first-line treatment for migraine, against ischemic nerve injury in vitro and in vivo.

Dihydroergotamine Tartrate Induces Lung Cancer Cell Death through Apoptosis and Mitophagy

BACKGROUND

Mitochondria have emerged as a major target for anticancer therapy because of their critical role in cancer cell survival. Our preliminary works have suggested that dihydroergotamine tartrate (DHE), an antimigraine agent, may have effects on mitochondria.

METHODS

We examined the effect of DHE on the survival of several lung cancer cells and confirmed that DHE suppressed diverse lung cancer cell growth effectively. To confirm whether such effects of DHE would be associated with mitochondria, A549 cells were employed for the evaluation of several important parameters, such as membrane potential, reactive oxygen species (ROS) generation, apoptosis, ATP production and autophagy.

RESULTS

DHE decreased membrane permeability, increased ROS generation as well as apoptosis, and disturbed ATP production. Eventually, mitophagy was activated for damaged mitochondria.

CONCLUSION

Taken together, our findings demonstrate that DHE induces lung cancer cell death by the induction of apoptosis and mitophagy, thus suggesting that DHE can be developed as an anti-lung cancer therapeutic agent.

The effects of serotonin/norepinephrine reuptake inhibitors and serotonin receptor agonist on morphine analgesia and tolerance in rats

Several studies have demonstrated that serotonergic and noradrenergic systems have important roles in morphine analgesia and tolerance. However, the exact mechanism underlying the development of morphine tolerance is not fully understood. The aim of this study was to investigate the possible role of serotonin/norepinephrine reuptake inhibitors (amitriptyline, venlafaxine) and serotonin receptor (5-HT(1A) and 5-HT(1B/1D)) agonist (dihydroergotamine) in morphine analgesia and tolerance in rats. To constitute morphine tolerance, animals received morphine (50 mg/kg; s.c.) once daily for 3 days. After the last dose of morphine was injected on day 4, morphine tolerance was evaluated. The analgesic effects of amitriptyline (20 mg/kg; i.p.), venlafaxine (20 mg/kg; s.c.), dihydroergotamine (100 μg/kg; i.v.) and morphine (5 mg/kg) were considered at 15- to 30-min intervals (0, 15, 30, 60, 90, and 120 min) by tail-flick and hot-plate analgesia tests. In this study, the data obtained suggested that amitriptyline and venlafaxine significantly increased the analgesic effect of morphine and attenuated the expression of morphine tolerance. However, dihydroergotamine significantly increased the analgesic effect of morphine but did not reduce the expression of morphine tolerance. In conclusion, we determined that co-administration of morphine with amitriptyline and venlafaxine increased the analgesic effects of morphine and attenuated the morphine analgesic tolerance.

Involvement of signaling pathways in bovine sperm motility, and effect of ergot alkaloids

There is evidence that ergot alkaloids can directly interact with mammalian spermatozoa affecting sperm functions. Ergot alkaloids exert their toxic or pharmaceutical effects through membrane receptor-mediated activities. This study investigated the signaling pathways involved in the in vitro inhibitory effects of both ergotamine (ET) and dihydroergotamine (DEHT) on the relative motility of bovine spermatozoa using specific inhibitors. Motile bovine spermatozoa were prepared using a Percoll gradient and incubated with ergot alkaloids with and without signaling pathway inhibitors. Co-incubation of ET or DHET with 100 microM prazosin (alpha 1-adrenergic receptor inhibitor) decreased (p < 0.05) relative motility of spermatozoa when compared with controls. In addition, preincubation of spermatozoa with 10 or 20 microM prazosin and DHET also reduced (p < 0.05) the number of motile spermatozoa. Relative sperm motility (motility of treated spermatozoa normalized to control sperm motility) was increased (p < 0.05) when co-incubations included ET and yohimbine (alpha 2-adrenergic receptor inhibitor); conversely, co-incubation of yohimbine (100 microM) and DHET decreased (p < 0.05) the percentage of motile spermatozoa when compared with controls. Pertussis toxin and cholera toxin (effectors of inhibitory and stimulatory G-proteins, respectively) altered (p < 0.05) relative sperm motility in a concentration dependent manner; however, co-incubation of pertussis or cholera toxin with ergot alkaloids had no interactive (p = 0.83) effects on the relative motility of spermatozoa. Co-incubation of Rp-cAMP (a membrane-permeable cAMP inhibitor) with 50 microM DHET had no effect (p > 0.05) on relative sperm motility; whereas, the co-incubation of 22.4 or 44.8 microM Rp-cAMP with 50 microM ET increased (p < 0.05) the percentage of motile spermatozoa when compared with 0 or 224 microM Rp-cAMP (49%, 65%, 59%, and 54%, respectively, for 0, 22.4, 44.8, and 224 microM of Rp-cAMP. An interaction between BAPTA-AM (a chelator of intracellular calcium) and alkaloids also impacted (p < 0.05) relative sperm motility. Generally, co-incubating spermatozoa with BAPTA-AM and ET increased the percentage of motile spermatozoa; however, co-incubation with DHET decreased relative sperm motility except with 41 microM BAPTA-AM. Collectively, these observations suggest that ET and DHET decreased the percentage of motile bovine spermatozoa via alpha adrenergic receptors. However, the second messenger systems involved with ergot alkaloid inhibition of relative motility of bovine spermatozoa remain to be elucidated.

In vivo pharmacodynamic interactions between two drugs used in orthostatic hypotension ? midodrine and dihydroergotamine

A combination of midodrine and dihydroergotamine (DHE) is frequently used clinically in patients suffering from severe orthostatic hypotension (OH). Whereas midodrine acts as a selective, peripheral alpha1-receptor agonist, DHE displays complex pharmacology and can behave as an alpha-adrenergic receptor agonist or antagonist. Surprisingly, the consequences of such a combination on blood pressure have never been investigated. The present study was performed in order to evaluate the pressor effects induced by the administration of both midodrine and DHE in old conscious dogs (n = 6) in experimental condition reproducing autonomic failure-related baroreflex dysfunction (atropine 0.1 mg/kg). For this purpose, we first studied the relative potency and intrinsic activity of each agonist and noradrenaline (NA) for the alpha1-adrenergic receptor. The orders of potency obtained in our study were 0.35, 11 and 400 microg/kg for NA, DHE and midodrine, and intrinsic activity: NA > midodrine > DHE. These results strongly suggest that DHE really acts in vivo as an alpha1-adrenoceptor partial agonist. Afterwards, the pressor effects of coadministration of midodrine (0.4 mg/kg) and DHE (15 microg/kg) were investigated: in one setting, midodrine was first administered, followed by DHE; in another, DHE was first administered, followed by midodrine. Our results show that in conscious dogs, the combination of midodrine and DHE leads to near-complete abolition of the pressor effect induced by the first administered drug. This in vivo proof of such antagonistic effects on blood pressure could explain clinical observations of worsening of OH in humans administered midodrine plus DHE. Although in vivo results obtained in conscious healthy dogs need to be experimentally and clinically confirmed in humans suffering from OH, these results strongly suggest that a midodrine-DHE combined treatment should be avoided in clinical practice.

Cardiovascular excitatory effect on rats of a fraction isolated from the eyestalk of shrimp: Peneaus vanameii

The crustacean nervous system is an important source of substances with diverse biological activities, particularly affecting invertebrate cardiocirculatory physiology. However, the effects of these substances on the cardiovascular system of higher vertebrates are not very well documented. The purpose of this study was to evaluate the effects of a cardioexcitatory substance (CES) isolated from the eyestalk of the shrimp Peneaus vanameii on rat cardiovascular function. The administration of a purified fraction of this substance raised mean arterial pressure by 37.33 +/- 5.00 mm Hg, pulse pressure 35.00 +/- 4.93 mm Hg and heart rate 80.00 +/- 12.83 beats/min over basal values (p < 0.01). Evaluation of the possible underlying mechanisms of this hypertensive and tachycardic effect reveled that dihydroergotamine pretreatment (20 microg/0.2 mL) reduced the effect of CES on mean blood pressure, but not on heart rate. Propranolol pretreatment (4 microg/0.2 mL) reduced the tachycardia, but not the hypertensive response. Enalapril pretreatment (5 microg/0.2 mL) did not modify the effects induced by CES on heart rate or blood pressure, and the verapamil pretreatment (1 microg/0.2 mL) reduced both cardiovascular changes by 85% (p < 0.01). These results indicate that CES isolated from the shrimp eyestalk produces hypertension and tachycardia mediated by adrenergic receptors in association to calcium channels activation.

Mechanisms of Regulation of Erythropoiesis during Experimental Neuroses

We studied the mechanisms of erythropoiesis regulation in a conflict situation and during paradoxical sleep deprivation. Plastic reconstruction of the erythroid hemopoietic stem during experimental neuroses is regulated by a complex multicomponent and multilevel system. This system consists of central adrenergic structures, sympathetic part of the autonomic nervous system, and alpha- and beta-adrenoceptors on erythroid precursors and cells of the hemopoietic microenvironment. Erythroid cells receive instructive information from the central nervous system via adrenoceptors on cells of the hemopoiesis-inducing microenvironment and erythroid precursors. Hyperplasia (conflict situation) and suppression of erythropoiesis (paradoxical sleep deprivation) are associated with specificity of central adrenergic regulatory mechanisms.

Evaluation of the anti-emetic potential of anti-migraine drugs to prevent resiniferatoxin-induced emesis in Suncus murinus (house musk shrew)

Activation of vanilloid receptors has commonly been used to facilitate neurogenic inflammation and plasma exudation to model components of the pathogenesis of migraine; however, these studies have been performed mainly in species lacking the emetic reflex. In the present studies, therefore, we used Suncus murinus, a species of insectivore capable of emesis, to investigate if the vanilloid receptor agonist resiniferatoxin is capable of modeling the emesis associated with migraine. Resiniferatoxin (100 nmol/kg, s.c.) induced an emetic response that was antagonized significantly (P<0.05) by ruthenium red (1-3 micromol), (2R-trans)-4-[1-[3,5-bis(trifluromethyl)benzoyl]-2-(phenylmethyl)-4-piperidinyl]-N-(2,6-dimethylphenyl)-1-acetamide (S)-hydroxybutanedioate (R116301; 10-100 micromol/kg), and scopolamine (1 micromol/kg), but not by dihydroergotamine (0.3-3 micromol/kg), sumatriptan (1-10 micromol/kg), methysergide (1-10 micromol/kg), tropanyl 3,5-dichlorobenzoate (MDL72222; 3-30 micromol/kg), ondansetron (0.3-3 micromol/kg), metoclopramide (3-30 micromol/kg), domperidone (3-30 micromol/kg), diphenhydramine (1-10 micromol/kg), or indomethacin (3-30 micromol/kg). The failure of a wide range of representative anti-migraine drugs to reduce retching and vomiting limits the use of this model to identify/investigate novel treatments for the emesis (and nausea) associated with migraine attacks in humans. However, the results provide further evidence for the involvement of a novel vanilloid receptor in resiniferatoxin-induced emesis and implicate both tachykinins and acetylcholine in the pathway(s) activated by resiniferatoxin in S. murinus.

5-HT1B receptors and alpha 2A/2C-adrenoceptors mediate external carotid vasoconstriction to dihydroergotamine

Dihydroergotamine produces external carotid vasoconstriction in vagosympathectomized dogs by 5-HT(1B/1D) receptors and alpha(2)-adrenoceptors. This study identified the specific subtypes involved in this response. One-minute intracarotid infusions of dihydroergotamine (5.6-10 microg/min) dose-dependently decreased external carotid blood flow without affecting blood pressure or heart rate. This response was: (1) partly blocked in dogs pretreated intravenously with the antagonists SB224289 (5-HT(1B); 2,3,6,7-tetrahydro-1'-methyl-5-[2'-methyl-4' (5-methyl-1,2,4-oxadiazol-3-yl)biphenyl-4-carbonyl]furo[2,3-f]indole-3-spiro-4'-piperidine hydrochloride), rauwolscine (alpha(2)), BRL44408 (alpha(2A); 2-[2H-(1-methyl-1,3-dihydroisoindole)methyl]-4,5-dihydroimidazole) or MK912 (alpha(2C); (2S,12bS)-1'3'-dimethylspiro(1,3,4,5',6,6',7,12b-octahydro-2Hbenzo[b]furo[2,3-a]quinazoline)-2,4'-pyrimidin-2'-one); (2) markedly blocked after SB224289 plus rauwolscine; and (3) unaffected after BRL15572 (5-HT(1D); 1-(3-chlorophenyl)-4-[3,3-diphenyl (2-(S,R) hydroxypropanyl) piperazine] hydrochloride) or imiloxan (alpha(2B)). Therefore, the above response involves 5-HT(1B) receptors and alpha(2A/2C)-adrenoceptors.

[Ultrasonographic evaluation of the venous tone in humans in the clinical pharmacology of venotropic drugs]

A new ultrasonographic method of evaluation of the venous tone in humans is described and experimentally justified. The method is based on the principles of venous occlusion plethysmograhy and ultrasonographic two-dimensional imaging of the cross section of cubital veins. It is found that an increment of the cross-sectional area of the vein is correlated with a change in the volume of distal segment of the upper extremity according to the data of aqueous plethysmography. The tests with nitroglycerin and dihydroergotamine (vasoactive drugs producing opposite effects upon the venous tone) confirmed the possibility of using this technique in the clinical pharmacology of venotropic drugs.

Agonist actions of dihydroergotamine at 5-HT2B and 5-HT2C receptors and their possible relevance to antimigraine efficacy

1. The pharmaceutical compound, dihydroergotamine (DHE) is dispensed to prevent and reduce the occurrence of migraine attacks. Although still controversial, the prophylactic effect of this drug is believed to be caused through blockade and/or activation of numerous receptors including serotonin (5-HT) receptors of the 5-HT2 subtype. 2. To elucidate if 5-HT2 receptors (5-HT2Rs) may be involved in DHE prophylactic effect, we performed investigations aimed to determine the respective pharmacological profile of DHE and of its major metabolite 8'-hydroxy-DHE (8'-OH-DHE) at the 5-HT2B and 5-HT2CRs by binding, inositol triphosphate (IP3) or cyclic GMP (cGMP) coupling studies in transfected fibroblasts. 3. DHE and 8'-OH-DHE are competitive compounds at 5-HT2B and 5-HT2CRs. 8'-OH-DHE interaction at (5-HT2BRs) was best fitted by a biphasic competition curve and displayed the highest affinity with a Ki of 5 nm. These two compounds acted as agonists for both receptors in respect to cGMP production with pEC50 of 8.32+/-0.09 for 8'-OH-DHE at 5-HT2B and 7.83+/-0.06 at 5-HT2CRs. 4. Knowing that the antimigraine prophylactic effect of DHE is only observed after long-term treatment, we chronically exposed the recombinant cells to DHE and 8'-OH-DHE. The number of 5-HT2BR-binding sites was always more affected than 5-HT2CRs. At 5-HT2BRs, 8'-OH-DHE was more effective than DHE, with an uncoupling that persisted for more than 40 h for IP3 or cGMP. By contrast, the 5-HT2CR coupling was reversible after either treatment. 5. Chronic exposure to 8'-OH-DHE caused a persistent agonist-mediated desensitisation of 5-HT2B, but not 5-HT2CRs. This may be of relevance to therapeutic actions of the compound.

Dihydroergotamine and its metabolite, 8'-hydroxy-dihydroergotamine, as 5-HT1A receptor agonists in the rat brain

1 In addition to stopping migraine attacks, dihydroergotamine (DHE) is an efficient drug for migraine prophylaxis. Whether 5-HT(1A) receptors could contribute to the latter action was assessed by investigating the effects of DHE and its metabolite, 8'-OH-DHE, on these receptors in the rat brain. 2 Membrane binding assays with [(3)H]8-OH-DPAT and [(3)H]WAY 100635 as radioligands showed that both DHE (IC(50)=28-30 nM) and 8'-OH-DHE (IC(50)=8-11 nM) are high-affinity 5-HT(1A) receptor ligands. 3 Both DHE and 8'-OH-DHE enhanced the specific binding of [(35)S]GTP-gamma-S to the dorsal raphe nucleus and the hippocampus in brain sections, but to a lower extent than 5-carboxamido-tryptamine (5-CT) in the latter area. 4 Both DHE (EC(50)=10.9+/-0.3 nM) and 8'-OH-DHE (EC(50)=30.4+/-0.8 nM) inhibited the firing of serotoninergic neurons in the dorsal raphe nucleus within brain stem slices. 5 Intracellular recording showed that 8'-OH-DHE was more potent than DHE to hyperpolarize CA1 pyramidal cells in rat hippocampal slices. 6 Both the stimulatory effects of DHE and 8'-OH-DHE on [(35)S]GTP-gamma-S binding and their electrophysiological effects were completely prevented by the selective 5-HT(1A) receptor antagonist WAY 100635. 7 As expected of 5-HT(1A) receptor partial agonists, DHE and 8'-OH-DHE prevented any subsequent hyperpolarization of CA1 pyramidal cells by 5-HT or 5-CT. 8 Through their actions at 5-HT(1A) auto- (in the dorsal raphe nucleus) and hetero-(notably in the hippocampus) receptors, DHE, and even more its metabolite 8'-OH-DHE, can exert both an inhibitory influence on neuronal excitability and anxiolytic effects which might contribute to their antimigraine prophylactic efficiency.

Modulation of cytochrome P450 metabolism by ergonovine and dihydroergotamine

This study investigated modulation of the cytochrome P450 3A (CYP3A4)-mediated metabolism of ergotamine (ET) by ergonovine and dihydroergotamine. Liver microsomes were prepared from rats treated i.p. for 4 d with: low (10 mM) or high (100 mM) levels of dexamethasone (DM10 and DM100), dihydroergotamine, ergonovine, or control. Cytochrome P450 activity was evaluated using ET and its isomers as substrate. Ergotamine was converted to its metabolites at rates of 0.385 or 0.535 (SE = 0.040) nM/microg protein/min when incubated with liver microsomes from DM10 or DM100 treated rats, respectively. These rates were higher than for rats on other treatments. Induction of CYP34A activity was not greater for ergonovine or dihydroergotamine treatments than for controls. Both ergonovine and dihydroergotamine treatments inhibited in vitro CYP3A4 activity in a dose dependent manner producing quadratic inhibition curves.

Ergotamine and dihydroergotamine: history, pharmacology, and efficacy

Ergotamine and dihydroergotamine share structural similarities with the adrenergic, dopaminergic, and serotonergic neurotransmitters. As a result, they have wide-ranging effects on the physiologic processes that they mediate. Ergotamine and dihydroergotamine are highly potent at the 5-HT1B and 5-HT1D antimigraine receptors and, as a consequence, the plasma concentrations that are necessary to produce the appropriate therapeutic and physiologic effects are very low. The broad spectrum of activity at other monoamine receptors is responsible for their side effect profile (dysphoria, nausea, emesis, unnecessary vascular effects). Both ergotamine and dihydroergotamine have sustained vasoconstrictor actions. In acute migraine treatment, their mechanisms of action involve constricting the pain-producing intracranial extracerebral blood vessels at the 5-HT1B receptors and inhibiting the trigeminal neurotransmission at the peripheral and central 5-HT1D receptors. The scientific evidence for efficacy is stronger for dihydroergotamine than for ergotamine. Their wide use is based on long-term experience.

Constitutive nitric oxide synthase inhibition combined with histamine and serotonin receptor blockade improves the initial ovalbumin-induced arterial hypotension but decreases the survival time in brown norway rats anaphylactic shock

Anaphylactic shock accidents after allergen exposure are frequent. After immunization with ovalbumin (OVA), a common dietary constituent, we evaluated the efficacy of pretreatment with histamine-receptor or serotonin-receptor blockers administered alone or in combination with a nitric oxide synthase inhibitor (L-NAME) on OVA-induced anaphylactic shock in Brown Norway rats. Animals were allocated to the following groups (n = 6 each): control (0.9% saline); diphenydramine (15 mg kg(-1)); cimetidine (20 mg kg(-1)); diphenydramine + cimetidine; dihydroergotamine (50 microg kg(-1)); diphenydramine + cimetidine + dihydroergotamine; L-NAME (100 mg/kg) alone or associated with diphenydramine, cimetidine, diphenydramine + cimetidine, dihydroergotamine, or diphenydramine + cimetidine + dihydroergotamine. Mean arterial blood pressure (MABP), heart rate (HR), and survival time were monitored for 60 min following treatment. The shock was initiated with i.v. OVA. The MABP drop after i.v. OVA was worsened by diphenydramine and was modestly attenuated by cimetidine, dihydroergotamine, or both together. L-NAME potentiated slightly the effects of cimetidine and dihydroergotamine by lessening the initial MABP decrease, but this transient effect was not sufficient to prevent the final collapse or to improve survival time. Decreased vasodilatory (prostaglandins E2), increased vasoconstrictory (thromboxane B2) prostaglandins, and unchanged leukotriene C4 concentrations were contributory to the overall hemodynamic changes. Thus, the combined blockade of vasodilator mediators (histamine, serotonin, and nitric oxide) slowed the MABP drop in anaphylactic shock, but did not improve survival. More studies are needed to understand these discordant effects.

The antimigraine 5-HT 1B/1D receptor agonists, sumatriptan, zolmitriptan and dihydroergotamine, attenuate pain-related behaviour in a rat model of trigeminal neuropathic pain

1. Peripheral lesion to the trigeminal nerve may induce severe pain states. Several lines of evidence have suggested that the antimigraine effect of the triptans with 5-HT(1B/1D) receptor agonist properties may result from inhibition of nociceptive transmission in the spinal nucleus of the trigeminal nerve by these drugs. On this basis, we have assessed the potential antinociceptive effects of sumatriptan and zolmitriptan, compared to dihydroergotamine (DHE), in a rat model of trigeminal neuropathic pain. 2. Chronic constriction injury was produced by two loose ligatures of the infraorbital nerve on the right side. Responsiveness to von Frey filament stimulation of the vibrissal pad was used to evaluate allodynia. 3. Two weeks after ligatures, rats with a chronic constriction of the right infraorbital nerve displayed bilateral mechanical hyper-responsiveness to von Frey filament stimulation of the vibrissal pad with a mean threshold of 0.38+/-0.04 g on the injured side and of 0.43+/-0.04 g on the contralateral (left) side (versus > or =12.5 g on both sides in the same rats prior to nerve constriction injury). 4. Sumatriptan at a clinically relevant dose (100 microg kg(-1), s.c.) led to a significant reduction of the mechanical allodynia-like behaviour on both the injured and the contralateral sides (peak-effects 6.3+/-1.1 g and 4.4+/-0.7 g, respectively). A more pronounced effect was obtained with zolmitriptan (100 microg kg(-1), s.c.) (peak-effects: 7.4+/-0.9 g and 3.2+/-1.3 g) whereas DHE (50-100 microg kg(-1), i.v.) was less active (peak-effect approximately 1.5 g). 5. Subcutaneous pretreatment with the 5-HT(1B/1D) receptor antagonist, GR 127935 (3 mg kg(-1)), prevented the anti-allodynia-like effects of triptans and DHE. Pretreatment with the 5-HT(1A) receptor antagonist, WAY 100635 (2 mg kg(-1), s.c.), did not alter the effect of triptans but significantly enhanced that of DHE (peak effect 4.3+/-0.5 g). 6. In a rat model of peripheral neuropathic pain, which consisted of a unilateral loose constriction of the sciatic nerve, neither sumatriptan (50-300 microg kg(-1)) nor zolmitriptan (50-300 microg kg(-1)) modified the thresholds for paw withdrawal and vocalization in response to noxious mechanical stimulation. 7. These results support the rationale for exploring the clinical efficacy of brain penetrant 5-HT(1B/1D) receptor agonists as analgesics to reduce certain types of trigeminal neuropathic pain in humans.

Haemodynamic effects of three doses of dihydroergotamine during spinal anaesthesia

We performed a randomized study comparing the haemodynamic effects of three doses of the vasopressor dihydroergotamine (DHE) (5, 10 and 15 microg x kg(-1)) in 30 ASA 1 and 2 patients, aged 53-87 yr, undergoing spinal anaesthesia. Non-invasive systolic arterial pressure (SAP), heart rate and central venous pressure (CVP) were recorded continuously for 25 min. Intravenous fluids were withheld during this period. All three doses of DHE reversed the lowering effects of spinal anaesthesia on SAP and CVP (P<0.0001), and these effects were smooth in onset and sustained. Whereas the lowest (5 microg x kg(-1)) dose restored SAP and CVP to near prespinal values, the higher (10 and 15 microg x kg(-1)) doses resulted in above-baseline increases in SAP of 7% and in CVP of 2.7 cm H2O (P<0.05). The haemodynamic profile of DHE makes it a useful agent for managing hypotension during spinal anaesthesia. A dose of 5-10 microg x kg(-1) is recommended.

Dihydroergotamine: discrepancy between arterial, arteriolar and pharmacokinetic data

AIMS

To investigate the peripheral vascular effects and pharmacokinetics of dihydroergotamine (DHE) 0.5 mg after a single subcutaneous administration in humans.

METHODS

A double-blind, placebo-controlled cross-over study was performed in 10 healthy male subjects. A wash-out period of 2 weeks separated the two study periods. During each period, just before and at regular intervals after drug administration, vascular measurements were performed and venous blood samples were drawn. Vessel wall properties were assessed at the brachial artery, by ultrasound and applanation tonometry. Blood pressure and heart rate were recorded with an oscillometric device. Forearm blood flow was measured with venous occlusion plethysmography. For all parameter-time curves the area under the curve (AUC) was calculated. Differences in AUC after placebo and DHE (DeltaAUC) were analysed and the time-course of the difference assessed. DHE pharmacokinetics were analysed according to a two-compartment open model with an absorption phase.

RESULTS

AUC for blood pressure, heart rate and forearm vascular resistance did not change after DHE. Brachial artery diameter and compliance decreased (P < 0.01); DeltaAUC (95% confidence interval) equalled -8.81 mm h (-12.97/-4.65) and -0.98 mm2 kPa(-1) h (-1.61/-0.34), respectively. Diameter decreased (P < 0.05) from 1 until 24 h after DHE (peak decrease 9.7% at 10 h); compliance from 2 until 32 h (24.8% at 2 h). Time to reach maximum plasma concentration of DHE averaged 0.33 +/- 0.08 h (+/- s.e.mean); terminal half-life was 5.63 +/- 1.15 h.

CONCLUSIONS

DHE decreased diameter and compliance of the brachial artery whereas forearm vascular resistance remained unchanged. Thus, DHE acts on conduit arteries without affecting resistance arteries. Furthermore, a discrepancy was demonstrated between the plasma concentrations of DHE which rapidly reach peak levels and quickly decline, and its long lasting vasoconstrictor activity.

Neurogenic inflammation in the context of migraine

Despite considerable research into the pathogenesis of idiopathic headaches, such as migraine, the pathophysiological mechanisms underlying them remain poorly understood. Although it is well established that the trigeminal nerve becomes activated during migraine, the consequences of this activation remain controversial. One theory, based on preclinical observations, is that activation of trigeminal sensory fibers leads to a painful neurogenic inflammation within the meningeal (dural) vasculature mediated by neuropeptide release from trigeminal sensory fibres and characterized by plasma protein extravasation, vasodilation, and mast cell degranulation. Effective antimigraine agents such as ergots, triptans, opioids, and valproate inhibit preclinical neurogenic dural extravasation, suggesting that this activity may be a predictor of potential clinical efficacy of novel agents. However, several clinical trials with other agents that inhibit this process preclinically have failed to show efficacy in the acute treatment of migraine in man. Alternatively, it has been proposed that painful neurogenic vasodilation of meningeal blood vessels could be a key component of the inflammatory process during migraine headache. This view is supported by the observation that jugular plasma levels of the potent vasodilator, calcitonin gene-related peptide (CGRP) are elevated during the headache and normalized by successful sumatriptan treatment. Preclinically, activation of trigeminal sensory fibers evokes a CGRP-mediated neurogenic dural vasodilation, which is blocked by dihydroergotamine, triptans, and opioids but unaffected by NK1 receptor antagonists that failed in clinical trials. These observations suggest that CGRP release with associated neurogenic dural vasodilation may be important in the generation of migraine pain, a theory that would ultimately be tested by the clinical testing of a CGRP receptor antagonist.

Canine external carotid vasoconstriction to methysergide, ergotamine and dihydroergotamine: role of 5-HT1B/1D receptors and alpha2-adrenoceptors

The antimigraine drugs methysergide, ergotamine and dihydroergotamine (DHE) produce selective vasoconstriction in the external carotid bed of vagosympathectomized dogs anaesthetized with pentobarbital and artificially respired, but the receptors involved have not yet been completely characterized. Since the above drugs display affinity for several binding sites, including alpha-adrenoceptors and several 5-HT1 and 5-HT2 receptor subtypes, this study has analysed the mechanisms involved in the above responses. Intracarotid (i.c.) infusions during 1 min of methysergide (31-310 microg min(-1)), ergotamine (0.56-5.6 microg min(-1)) or DHE (5.6-31 microg min(-1)) dose-dependently reduced external carotid blood flow (ECBF) by up to 46+/-4, 37+/-4 and 49+/-5%, respectively. Blood pressure and heart rate remained unchanged. The reductions in ECBF by methysergide were abolished and even reversed to increases in animals pre-treated with GR127935 (10 microg kg(-1), i.v.). The reductions in ECBF by ergotamine and DHE remained unchanged in animals pre-treated (i.v.) with prazosin (300 microg kg(-1)), but were partly antagonized in animals pre-treated with either GR127935 (10 or 30 microg kg(-1)) or yohimbine (1000 microg kg(-1)). Pre-treatment with a combination of GR127935 (30 microg kg(-1)) and yohimbine (1000 microg kg(-1)) abolished the responses to both ergotamine and DHE. The above doses of antagonists were shown to produce selective antagonism at their respective receptors. These results suggest that the external carotid vasoconstrictor responses to methysergide primarily involve 5-HT1B/1D receptors, whereas those to ergotamine and DHE are mediated by 5-HT1B/1D receptors as well as alpha2-adrenoceptors.

Effects of sumatriptan on coronary flow and left ventricular function in the isolated perfused guinea pig heart

The effects of the 5-HT1B/D receptor agonist, sumatriptan, on coronary flow (CF) and left ventricular function in the isolated perfused guinea pig heart were investigated in the presence and absence of coronary endothelial dysfunction induced by nitric oxide (NO) synthase inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME; 10 microM). Hearts were perfused under constant pressure (80 cm H2O) with oxygenated (95% O2/5% CO2) Krebs bicarbonate buffer (pH 7.4) and were driven at 4 Hz. In the absence of L-NAME (n=37), sumatriptan (0.1-32 microM) failed statistically significantly to affect left ventricular developed pressure (LVDP; maximal change, -8.1+/-1.8%; NS vs. vehicle), left ventricular end-diastolic pressure (LVEDP; +10.4+/-9.8%, NS), or CF (-12.2+/-1.4%; NS compared with vehicle). L-NAME per se significantly reduced coronary flow (CF; -26.3+/-2.9%; p < 0.001), thereby increasing coronary vascular tone, and decreased LVDP (-17.1+/-1.8%; p < 0.01). In hearts perfused with L-NAME (10 microM; n=61), sumatriptan (0.1-32 microM) still failed significantly to affect CF (maximal change, 0.2+/-5.7%, NS) but concentration-dependently increased LVEDP [maximal increase, 89.0+/-30.3%; p < 0.05; geometric mean EC50 3.6 (2.9-5.7) microM], which was not prevented by the 5-HT1B/D receptor antagonist, GR 127935 (0.1 microM; maximal increase, 51.8+/-11.1%; n=48, NS compared with sumatriptan alone). In conclusion, sumatriptan failed significantly to affect CF even in the presence of endothelial dysfunction. LV function similarly remained unaffected in normal hearts, but sumatriptan produced diastolic contracture in the presence of coronary endothelial dysfunction by a mechanism apparently not involving 5-HT1B/D receptors. Collectively the data indicate that 5-HT1B/D receptor expression or effector coupling or both are absent or low in the guinea pig heart, because no detectable functional responses were observed.

Neural regulation of blood flow in the rat submandibular gland

Blood flow in salivary glands is regulated mainly by sympathetic and parasympathetic nerve activity. This study was carried out to determine the relative contributions of cholinergic, adrenergic and peptidergic neurotransmitters to the control of submandibular blood flow in the rat using laser-Doppler flowmetry. Parasympathetic impulses caused a rapid atropine-sensitive vasodilation followed by a maintained increase in blood flow, a portion of which remained in the presence of both atropine and L-NAME. In contrast, continuous sympathetic stimulation caused an intense vasoconstriction that was followed by a prolonged after-vasodilation. The same number of impulses delivered in bursts resulted in a cyclic vasoconstriction followed by a rapid vasodilation. Alpha-adrenoceptor blockade largely abolished the vasoconstriction, and the duration and magnitude of the after-vasodilation were reduced. Inhibition of nitric oxide (NO) synthase by L-NAME reduced the vasodilation. The addition of a beta-adrenoceptor antagonist eliminated the sympathetic vasodilator response, but in the presence of complete alpha- and beta-adrenoceptor blockade and L-NAME a small vasoconstriction remained. We conclude that the vasoconstrictor effects of sympathetic stimulation of the rat submandibular gland are due to alpha-adrenergic receptor activation and probably also NPY, and the vasodilator effects are due to NO and beta-adrenergic activity. Parasympathetic vasodilation was due to NO-independent mechanisms mediated by acetylcholine and substance P, and NO-dependent mechanisms mediated by VIP.

Contractile responses evoked by dihydroergotamine, naratriptan and sumatriptan in the canine isolated coronary artery

Contractile responses evoked by the 5-HT IB/D receptor agonists, dihydroergotamine, naratriptan and sumatriptan, were compared in canine isolated coronary artery rings before and after endothelial dysfunction as obtained by inhibition of nitric oxide synthase with Nw-nitro-L-arginine methyl ester (L-NAME; 10 microM). The three agonists contracted rings in the potency order of dihydroergotamine (geometric mean pD2 value with 95% confidence limits in parentheses: 6.9 [5.3-7.9] and 7.0 [5.4-7.3] in the absence and presence of nitric oxide synthase (NOS) inhibition [I], respectively) > or = naratriptan (6.8 [5.7-7.3] and 6.4 [5.7-6.6]) > sumatriptan (4.8 [3.6-5.6] and 5.0 [3.6-5.6]) independently of the presence or absence of L-NAME. In absence of L-NAME, efficacy, as assessed by the mean maximal contractile response (Emax), tended to be greater, although not significantly, for sumatriptan and naratriptan compared to dihydroergotamine. L-NAME per se markedly increased developed tension (43.0 +/- 4.6 mN; n = 50) and potentiated maximal responses (0.6 +/- 0.2 and 10.7 +/- 2.4 mN for dihydroergotamine in the absence and presence of L-NAME respectively; 1.7 +/- 0.6 and 18.7 +/- 3.7 mN for naratriptan; 2.5 +/- 0.6 and 21.3 +/- 3.8 mN for sumatriptan; P < 0.01 in each case). Emax values of sumatriptan and naratriptan were greater than those produced by dihydroergotamine in the presence of L-NAME but remained lower than the sub-maximal contractile responses evoked by the thromboxane A2 analogue, U-46619 (ie, 32.4 +/- 5.2 mN in the absence of L-NAME; n = 50), or L-NAME per se. In conclusion, 5-HT IB/D receptor agonist efficacies in contracting coronary arteries are relatively low under basal conditions and are potentiated in the presence of a dysfunctional endothelium, whereas agonist potencies remain unaffected.

Interaction of 5-HT1B/D ligands with recombinant h 5-HT1A receptors: intrinsic activity and modulation by G-protein activation state

Many 5-HT1B/D receptor ligands have affinity for 5-HT1A receptors. In the present study, the intrinsic activity of a series of 5-HT1B/D ligands was investigated at human 5-HT1A (h 5-HT1A) receptors by measuring G-protein activation in recombinant C6-glial and HeLa membranes, using agonist-stimulated [35S]GTPgammaS binding. In these two membrane preparations, the density of h 5-HT1A receptors (i.e., 246 to 320 fmol mg(-1) protein) and of their G-proteins, and the receptor: G-protein density ratio (0.08 to 0.18) appeared to be similar. It was found that: (i) the maximal [35S]GTPgammaS binding responses induced by the 5-HT1B/D receptor ligands in the HeLa preparation at 30 microM GDP were comparable to that of the native agonist 5-HT; (ii) as compared to 5-HT (1.00), similar potencies but lower maximal responses were observed in the C6-glial preparation at 0.3 microM GDP for zolmitriptan (0.89), dihydroergotamine (0.81), rizatriptan (0.71), CP122638 (0.69), naratriptan (0.60) and sumatriptan (0.53); and that (iii) maximal [35S]GTPgammaS binding responses induced by 5-HT1B/D ligands in the C6-glial preparation were either unaffected or significantly enhanced by increasing the GDP concentration from 0.3 to 30 microM and higher concentrations. These features differ from those observed with 5-HT1A receptor agonists; the latter display the same rank order of potency and efficacy in both membrane preparations, and increasing the amount of GDP with C6-glial membranes results in an attenuation of both the agonist's maximal effect and the apparent potency of partial agonists. The differential regulation of 5-HT1A and 5-HT1B/D agonist responses by GDP suggests that different G-protein subtypes are involved upon 5-HT1A receptor activation by 5-HT1A and 5-HT1B/D agonists.

Agonistic properties of alniditan, sumatriptan and dihydroergotamine on human 5-HT1B and 5-HT1D receptors expressed in various mammalian cell lines

1. Alniditan, a novel migraine abortive agent, is a potent 5-HT1B/5-HT1D receptor agonist of nM affinity. We compared the agonistic properties of alniditan, sumatriptan and dihydroergotamine on the cloned human 5-HT1B receptor expressed at 200 fmol mg(-1) protein (Bmax) in non-induced L929sA cells, at 740 fmol mg(-1) protein in HEK 293 and at 2300 fmol mg(-1) protein in mIFNbeta-induced L929sA cells, and on the human cloned 5-HT1D receptor expressed in C6 glioma cells (Bmax 780 fmol mg(-1) protein). 2. Sodium butyrate treatment increased the expression level of human (h)5-HT1B receptors in HEK 293 cells and h5-HT1D receptors in C6 glioma cells approximately 3 fold, the binding affinities of [3H]-5-HT and [3H]-alniditan were unaffected. 3. Agonistic properties were evaluated based on inhibition of cyclic AMP accumulation in the cells after stimulation of adenylyl cyclase by forskolin or isoproterenol. Alniditan, sumatriptan and dihydroergotamine were full agonists at the hS-HT1B receptor (IC50 values were 1.7, 20 and 2 nM, respectively in HEK 293 cells) and hS-HT1D receptors (IC50 values of 1.3, 2.6 and 2.2 nM, respectively). At the h5-HT1B receptor the agonist potency of the compounds slightly increased with higher receptor density. The opposite was seen for antagonists (ocaperidone, risperidone and ritanserin). 4. This comparative study demonstrated that alniditan was 10 times more potent than sumatriptan at the h5-HT1B receptor, and twice as potent at the h5-HT1D receptor. Dihydroergotamine was more potent an agonist at the h5-HT1B receptor when expressed at high and low level in L929sA cells (but not in HEK 293 cells), and was less potent at the hS-HT1D receptor.

Prediction of drug-drug interactions of zonisamide metabolism in humans from in vitro data

OBJECTIVE

The purposes of this study were to identify the P450 enzyme (CYP) responsible for zonisamide metabolism in humans by using expressed human CYPs and to predict drug interaction of zonisamide in vivo from in vitro data.

METHODS

Ten expressed human CYPs and human liver microsomes were used in the experiments for the identification of enzymes responsible for zonisamide metabolism and for the prediction of drug-drug interactions of zonisamide metabolism in humans from in vitro data, respectively. Two-sulfamoylacetyl phenol, a reductive metabolite of zonisamide, was measured by the HPLC method.

RESULTS

From the experiments using ten expressed human CYPs, CYP2C19, CYP3A4 and CYP3A5 were shown to be capable of catalyzing zonisamide reduction. However, an intrinsic clearance, Vmax/kM, of CYP3A4 was much higher than those of CYP2C19 and CYP3A5. From the point of view of enzyme amount in human liver CYPs isoform and their intrinsic clearance, it was suggested that CYP3A4 is mainly responsible for zonisamide metabolism in human CYPs. Zonisamide metabolism in human liver microsomes was markedly inhibited by cyclosporin A, dihydroergotamine, ketoconazole, itraconazole, miconazole and triazolam. We estimated the possibility and degree of change of zonisamide clearance in vivo in clinical dose range from in vitro inhibition constant of other drugs against zonisamide metabolism (Ki) and unbound inhibitor concentration in blood (Iu) in clinical usage. Clearance of zonisamide was maximally estimated to decrease by 31%, 23% and 17% of the clearance without inhibitors i.e. ketoconazole, cyclospolin A and miconazole, respectively. Fluconazole and carbamazepine are estimated to decrease by 5-6% of the clearance of zonisamide. On the other hand, there may be lack of interaction of zonisamide metabolism by dihydroergotamine, itraconazole and triazolam in clinical dose range.

CONCLUSION

We demonstrated that: (1) zonisamide is metabolized by recombinant CYP3A4, CYP2C19 and CYP3A5, (2) the metabolism is inhibited to a variable extent by known CYP3A4/5 substrates and/or inhibitors in human liver microsomes, and (3) in vitro-in vivo predictive calculations suggest that several compounds demonstrating CYP3A4-affinity might cause in vivo drug-drug interactions with zonisamide.

Effects of sympathetic nerve stimulation on membrane potential, [Ca2+]i and force in the arrested sinus venosus of the toad, Bufo marinus

1. The effects of sympathetic nerve stimulation on membrane potential and on the intracellular concentration of calcium ions, [Ca2+]i, were recorded concurrently from the sinus venosus of the toad, Bufo marinus, in preparations where beating had been abolished by adding an organic calcium antagonist to the physiological saline. In a separate set of experiments the effects of sympathetic nerve stimulation on force production were examined. 2. Stimulation of the sympathetic nerves caused a membrane depolarization and a simultaneous increase in [Ca2+]i. Both responses were reduced by dihydroergotamine (20 microM). 3. The membrane depolarization and increase in [Ca2+]i evoked by sympathetic nerve stimulation were abolished by ryanodine (10 microM), or caffeine (3 mM). The effects of caffeine, but not those of ryanodine, were fully reversible. 4. Although the Ca(2+)-ATPase inhibitor thapsigargin (30 microM) itself had little effect on the responses to sympathetic nerve stimulation, in its presence caffeine (3 mM) irreversibly abolished the responses. 5. In the presence of nifedipine (10 microM), sympathetic nerve stimulation caused contractions of the sinus venosus. These responses were abolished by either ryanodine (10 microM) or caffeine (3 mM). 6. The results suggest that neuronally released transmitter activates a complex biochemical pathway which triggers the release of Ca2+ from internal stores.

Effects of dihydroergotamine and sumatriptan on isolated human cerebral and peripheral arteries and veins

BACKGROUND

Pharmacological cerebral vasoconstriction has recently been suggested as treatment for patients with increased intracranial pressure (ICP) after severe traumatic brain lesions. Hypothetically, a moderate constriction of precapillary resistance vessels might be advantageous since it decreases intracapillary blood pressure, and a contraction of cerebral veins might effectively reduce intracranial blood volume and ICP. This report examines the in vitro effects of two vasoconstrictors, dihydroergotamine (DHE) and sumatriptan, which may be considered for treatment of increased ICP.

METHODS

The reactivity of isolated small human cerebral subcutaneous and omental arteries and veins were studied during exposure to different concentrations of DHE and sumatriptan.

RESULTS

Both sumatriptan and DHE induced concentration-dependent contractions in human cerebral arteries and veins and 50% of maximum contractions were obtained at significantly lower concentrations of DHE than of sumatriptan. The maximum contraction of cerebral arteries was significantly higher with sumatriptan than with DHE. Both drugs caused contractions of subcutaneous arteries at concentrations of 10(-7)-10(-6)M, which is within the therapeutic concentration range of sumatriptan, while no effect was obtained in omental vessels.

CONCLUSIONS

Both DHE and sumatriptan cause contraction of isolated human cortical arteries and veins at very low concentrations. The differences observed between the two drugs may be explained by the fact that DHE is an alpha-adrenergic as well as a 5-HT agonist while sumatriptan acts specifically on 5-HT receptors. The study supports the hypothesis underlying the use of DHE for the treatment of increased ICP in patients with severe traumatic brain lesions.

Agonist activity of antimigraine drugs at recombinant human 5-HT1A receptors: potential implications for prophylactic and acute therapy

The actions of several serotonergic ligands in use or under development for the treatment of migraine headaches were examined at recombinant human 5-HT1A receptors stably expressed in Chinese Hamster Ovary cells. Affinities (K(i)s) at this site were determined in competition binding experiments with [3H]-8-OH-DPAT ([3H](+/-)8-hydroxy-N,N-dipropylaminotetralin), whilst agonist efficacy was measured by stimulation of [35S]-GTP gamma S (guanylyl-5'-[gamma[35S]thio]-triphosphate) binding. Of the prophylactic antimigraine drugs tested, methysergide and lisuride behaved as efficacious agonists (Emax > or = 90% relative to 5-HT) whereas pitozifen and (-)propranolol acted as a partial agonist (60%) and an antagonist, respectively. This suggests that there is no correlation between agonism at 5-HT1A receptors and prophylactic antimigraine action. In contrast, serotonin, dihydroergotamine, sumatriptan, naratriptan and alniditan, which are effective in acute interruption of migraine attacks, each displayed high efficacy (Emax = 100, 100, 92.6, 79.3, 79.1% respectively) and marked affinity (Ki = 18.7, 0.6, 127, 26.4 and 3.0 nM respectively) at 5-HT1A receptors. EC50 values for agonist stimulation of [35S]-GTP gamma S binding correlated with respective Ki values at 5-HT1A receptors (r = 0.93) and the stimulation of [35S]-GTP gamma S binding by these compounds was antagonised by the selective 5-HT1A antagonist WAY 100,635 (N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridinyl) cyclo-hexanecarboxamide; 100 nM). These data suggest that agonism at 5-HT1A receptors may be involved in some actions of drugs used in acute antimigraine therapy. In comparison with the above compounds, novel ligands targeted at 5-HT1B/1D receptors, such as GR125,743 (N-[4-methoxy-3-(4-methyl-piperazin-1-yl)phenyl] -3-methyl-4-(4-pyridyl)benzamide) and GR 127,935 (N-[4-methoxy-3-(4-methylpiperazin-1-yl)-phenyl]-2'-methyl-4'-(5-m ethyl-1, 2,4-oxadiazol-3-yl)-biphenyl-4-carboxamide), only weakly activated [35S]-GTP gamma S binding (32.4 and 32.1% efficacy) and displayed moderate affinity at 5-HT1A receptors (Kis 53.1 and 49.8 nM) suggesting that they constitute useful tools to differentiate 5-HT1A and 5-HT1B/1D receptor-mediated actions. In conclusion, the present data indicates that several antimigraine agents exhibit marked 5-HT1A receptor activity and that although this is unlikely to be important for prophylactic action it may be relevant to the ancilliary properties of drugs used for acute migraine treatment.

The pharmacology of ergotamine and dihydroergotamine

The ergot alkaloids are a family of chemical entities that have many pharmacologic effects. Their diversity results from their interaction with multiple receptors, their variable receptor affinity and intrinsic activity, and their variable organ-specific receptor access. Ergotamine tartrate (ET) was one of the first ergot alkaloids to be isolated. Dihydroergotamine (DHE) is synthesized by reducing an unsaturated bond in ergotamine (E); this modification results in a changed pharmacologic profile. Dihydroergotamine exhibits greater alpha-adrenergic antagonist activity and much less potent arterial vasoconstriction and emetic potential. Both E and DHE are 5-HT1A, 5-HT1B, 5-HT1D, and 5-HT1F receptor agonists. The vasoconstrictor activities of these ergot compounds have long been believed to be the basis of their clinical effects, but recent evidence suggests that their antimigraine action may result in part from their inhibitory effects on neurogenic inflammation and neuronal transmission and not from vasoconstriction. Improvements in assay methodology have provided more accurate determination of the pharmacokinetics of E and DHE. The long duration of action appears to result from active metabolites and tight tissue binding. Intranasal (IN) administration of DHE delivers adequate plasma concentrations of the drug without the need for parenteral administration and should further expand its role in migraine pharmacotherapy.

Effects of ergotamine and dihydroergotamine on 5-hydroxytryptamine-2A receptors in the isolated rat aorta

Ergotamine contracted isolated rat aorta rings with an intrinsic activity of 50% of that of 5-hydroxytryptamine. (5-HT, 0.1 mmol/l). Dihydroergotamine did not contract the tissue, but insurmountably blocked contraction in response to ergotamine and 5-HT. The 5-HT2A receptor antagonist, ketanserin (0.1 mumol/l), inhibited ergotamine (pKB 8.0) and 5-HT (pKB 8.1) induced contractions. These results indicate that in the rat aorta ergotamine is a partial 5-HT2A receptor agonist, whilst dihydroergotamine is an insurmountable 5-HT2A receptor antagonist. The present data could explain why ergotamine displays more cardiovascular and uterotonic side effects than dihydroergotamine.

Locally formed 5-hydroxytryptamine stimulates phosphate transport in cultured opossum kidney cells and in rat kidney

Renal proximal tubular cells have been shown to express aromatic L-amino acid decarboxylase (L-AAAD), which converts L-dopa into dopamine and 5-hydroxytryptophan [(OH)Trp] into 5-hydroxytryptamine (5-HT; serotonin). Because 5-HT receptors have been demonstrated in proximal cells, we hypothesized that 5-HT may act as an autocrine/paracrine modulator of proximal transport. We evaluated this possibility in opossum kidney (OK) cells, a renal epithelial cell line with a proximal phenotype expressing 5-HT1B receptors, and in intact anaesthetized rats. 5-HT synthesis by OK cells increased with incubation time and (OH)Trp concentration, and was abolished by benserazide, an L-AAAD inhibitor. 5-HT reversed parathyroid hormone (PTH)-induced cAMP accumulation in a pertussis toxin-sensitive manner and reduced the PTH inhibition of P(i) uptake without affecting the NaP(i)-4 mRNA level. The effects of 5-HT on cAMP generation and Na-P(i) co-transport were reproduced by (OH)Trp, except in the presence of benserazide, and by L-propranolol and dihydroergotamine, two 5-HT1B receptor agonists. In rats, (OH)Trp and dihydroergotamine decreased fractional P(i) excretion. Benserazide abolished the effect of (OH)Trp but not that of dihydroergotamine.

IN CONCLUSION

(i) locally generated 5-HT blunts the inhibitory effect of PTH on Na-P(i) co-transport in OK cells; (ii) endogenous 5-HT decreases P(i) excretion in rats; and (iii) 5-HT is a paracrine modulator involved in the physiological regulation of renal P(i) transport.

Effect of antimigraine drugs on dural blood flows and resistances and the responses to trigeminal stimulation

The effects of 2 antimigraine drugs sumatriptan and dihydroergotamine on dilatation of the middle meningeal artery elicited by stimulation of the trigeminal ganglion at the entry point of the first and second divisions was investigated in cats. Carotid and middle meningeal arterial blood flows and resistances were measured in 9 cats anesthetised with chloralose. Electrical stimulation of either trigeminal ganglion produced a frequency-dependent decrease in resistance of the carotid artery ipsilaterally and the middle meningeal artery bilaterally. The intravenous injection of sumatriptan increased carotid and meningeal vascular resistance, but this response was not prolonged. The intravenous injection of dihydroergotamine produced a larger and more prolonged vasoconstriction in these 2 beds than did sumatriptan. Dihydroergotamine, but not sumatriptan, blocked some components of the vascular response induced by stimulation of the trigeminal ganglion. Dihydroergotamine and sumatriptan have a different spectrum of activity on cranial circulatory beds and neither of them is able to reduce trigeminal-induced vasodilatation by blocking antidromic activation of trigeminal nerve fibres in cats at the doses used in these experiments.

Endothelial 5-HT receptors mediate relaxation of porcine pulmonary arteries in response to ergotamine and dihydroergotamine

1. The aim of the present study was to investigate whether antimigraine ergot compounds may act at endothelial 5-hydroxytryptamine (5-HT) receptors which trigger the release of endothelium-derived relaxing factor (EDRF). Changes in tone of porcine isolated pulmonary arteries were measured isometrically. The integrity of the endothelium was assessed by the bradykinin-induced relaxation of prostaglandin F2 alpha (PGF2 alpha, 3 microM)-precontracted vessels. 2. The ergot derivatives ergotamine, dihydroergotamine (DHE) and dihydroergocristine, as well as 5-HT and (+/-)-alpha-methyl-5-HT, elicited a reversible endothelium-dependent relaxation of PGF2 alpha-precontracted arterial ring segments. The relaxation to both ergotamine and 5-HT was associated with an increase in cyclic GMP. After pretreatment of the vessels with NG-nitro-L-arginine methyl ester (200 microM), or removal of endothelium by mechanical rubbing, the relaxant responses were abolished. 3. The mean pEC50 values for relaxant responses followed the order: (+/-)-alpha-methyl-5-HT (8.80) > 5-HT (8.75) > ergotamine (8.17) > DHE (7.70) > 5-carboxamidotryptamine (7.62) > dihydroergocristine (7.17). 4. The relaxant effects of both ergotamine and dihydroergotamine were resistant to block by indomethacin (3 microM), prazosin (1 microM) and ketanserin (1 microM). However, the ergotamine-induced relaxation was highly susceptible to block by pizotifen (pA2 = 8.23), norclozapine (pA2 = 8.20), methiothepin (-log IC50 = 7.26), rauwolscine (pA2 = 7.24) and mesulergine (pA2 = 6.64). Each antagonist inhibited the relaxant responses to (+/-)-alpha-methyl-5-HT in the same manner with similar potency as that determined against ergotamine. 5. Recently, mRNA transcripts for 5-HT1D beta and 5-HT2B receptors have been demonstrated in porcine pulmonary arteries. The rank order of potencies of agonists and antagonists in the present study suggests that the relaxant responses to 5-HT and ergot derivatives are mediated through activation of endothelial 5-HT receptors which are similar to the 5-HT2B receptor subtypes.

5-Carboxamido-tryptamine, CP-122,288 and dihydroergotamine but not sumatriptan, CP-93,129, and serotonin-5-O-carboxymethyl-glycyl -tyrosinamide block dural plasma protein extravasation in knockout mice that lack 5-hydroxytryptamine1B receptors

We studied the dural plasma protein extravasation response after unilateral electrical stimulation of the trigeminal ganglion in mice lacking serotonin 5-HT1B (5-HT1D beta) receptors by modifying a technique previously described in rats or guinea pigs. We investigated the inhibitory effects of six 5-HT1 receptor agonists in this model: 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3,2-b]pyrid-5-one (CP-93,129), sumatriptan, serotonin-5-O-carboxymethyl-glycyl -tyrosinamide (GTI), 5-methylaminosulfonylmethyl-3-(N-methylpyrrolidin-2R -ylmethyl)-1H-indole (CP-122,288), 5-carboxamido-tryptamine (5-CT), and dihydroergotamine. The plasma extravasation response did not differ between wild-type and mutant after vehicle injection. The potency of sumatriptan, CP-122,288, CP-93,129, and 5-CT in wild-type mice was similar to that previously reported for rats. CP-122,288 (1 nmol kg), 5-CT (1 nmol/kg), and dihydroergotamine (72 nmol/kg) inhibited plasma protein extravasation within dura mater after electrical trigeminal ganglion stimulation in both wild-type and knockout mice, which suggests that these agonists act predominantly via receptors other than 5-HT1B. Unlike the wild-type mice, CP-93,129 (1.4 mumol/kg), a specific 5-HT1B receptor agonist, had no effect in knockout mice. The same held true for sumatriptan (0.7 mumol/kg) and GTI (0.6 mumol/kg). These results suggest that CP-93,129, sumatriptan, and GTI exert their effects via 5-HT1B (5-HT1D beta) receptors in mice.

Central activation of the trigeminovascular pathway in the cat is inhibited by dihydroergotamine. A c-Fos and electrophysiological study

Recent studies have delineated a clear role for the trigeminal innervation of pain-sensitive intracranial structures in the pathophysiology of migraine. The development of new compounds for the treatment of the acute attack of migraine has led to a greater understanding of serotonin (5-hydroxytryptamine; 5HT) receptor diversity. The ergot alkaloids have been used in the treatment of acute attacks of migraine for many years and parenteral administration of dihydroergotamine (DHE) can be a useful treatment strategy. In this study, the question of a possible central site of action of DHE is considered using both anatomical and physiological approaches. The c-Fos method has been used to map functional activation of central neurons in response to stimulation of the superior sagittal sinus (SSS) in the cat. This structure has been used as it refers pain to the ophthalmic division of the trigeminal nerve in humans, and in cats induces changes in neuropeptides and cranial blood flow similar to those seen in migraine. In addition, the temporal aspects of the effect of DHE have been studied by making extracellular recordings from cells in the most caudal aspect of the trigeminal nuclear complex. Stimulation of the SSS results in Fos expression in the superfical laminae of the trigeminal nucleus caudalis and in the dorsal horn of C1 and C2. This activation is blocked by a clinically relevant dose of DHE. Similarly, cells can be recorded in this region that respond to SSS stimulation. This linked cellular activity can be inhibited by the same intravenous dose of DHE. Together, these studies show that DHE can inhibit activity in central trigeminal neurons. Since the sinus and its nerve supply are directly stimulated, the peripheral nerve/vessel innervation is bypassed and this inhibition cannot have happened at any other site. These data imply that drugs acting at the central trigeminal neurons may have a role in the treatment of acute attacks of migraine.

Effects of dihydroergotamine on cerebral circulation during experimental intracranial hypertension

Different cerebral vasoconstrictors have recently been suggested for the treatment of raised intracranial pressure (ICP), in patients with severe traumatic brain lesions. Such treatment may be associated with severe side effects. A porcine model simulating an intracranial mass lesion was utilized to examine the haemodynamic cerebral effects of dihydroergotamine (DHE), a recently introduced pharmacological treatment for raised intracranial pressure. Intracranial hypertension was induced by inflation of two tonometric gastric balloons placed extradurally covering the parieto-occipital region bilaterally. The animals were randomized into one group with six animals receiving 1.0 mg of DHE i.v. followed by a continuous infusion of 0.2 mg/h (high dose) and another group of six animals receiving 0.15 mg i.v. followed by 0.03 mg/h (low dose). Measurements of cerebral blood flow (CBF) and arterio-venous difference in oxygen content (CaVO2) were performed by 5, 20 and 60 min after the DHE infusion. Intracranial pressure (ICP), mean arterial blood pressure (MAP) and cerebral electrical activity (EEG) were recorded continuously. In both groups infusion of DHE caused a lasting decrease in ICP probably achieved mainly by a decrease in cerebral blood volume due to constriction of both arterial and venous capacitance vessels. In the group treated with high-dose DHE, but not in that given low-dose DHE, a progressive increase in CaVO2, a fall in jugular venous pH and an increase in EEG delta activity were observed indicating cerebral hypoxia. The study supports the view that DHE may be a valuable tool in the pharmacological treatment of increased ICP in traumatic brain lesions but underscores the importance of a proper dosage.

Carotid blood flow distribution, haemodynamics and inotropic responses following calcitonin gene-related peptide in the pig

The sensory neuropeptide, calcitonin gene-related peptide (alpha-CGRP), has been implicated in the pathogenesis of migraine headache. The present study aimed to evaluate the effects of intracarotid infusions of human alpha-CGRP (10, 30 and 100 pmol/kg.min; n = 8), as compared to that of saline (4 times; n = 8) on haemodynamics and blood flow distribution within the carotid circulation of the anaesthetized pig, using the radioactive microsphere method. Furthermore, the effects of antimigraine drugs, dihydroergotamine (100 micrograms/kg i.v.; n = 4) or sumatriptan (300 micrograms/kg i.v.; n = 4), on these parameters were studied in the presence of the infusion of the highest concentration of human alpha-CGRP. Additionally, putative positive inotropic responses to human alpha-CGRP (10(-9)-10(-7) M) were investigated in porcine isolated atrial and ventricular trabeculae. Human alpha-CGRP increased carotid artery blood flow and conductance dose-dependently, together with an enhancement in vascular pulsations. These effects were associated with a fall in systemic blood pressure with concomitant increases in heart rate and cardiac output. The increase in carotid blood flow was reflected by an increase in total capillary blood flow, predominantly to extracerebral tissues including the dura, whereas blood flow through arteriovenous anastomoses remained stable. Both dihydroergotamine and sumatriptan reduced carotid blood flow and its capillary fraction without affecting systemic vascular conductance. In tissues, these drugs reversed blood flow increases due to human alpha-CGRP in most extracerebral tissues, but failed to reduce dural blood flow. In porcine isolated atrial and ventricular trabeculae, noradrenaline (10(-8)-10(-5) M) increased force of contraction in a concentration-dependent manner. In contrast, human alpha-CGRP (10(-9)-10(-7) M) failed to increase force of contraction in atrial trabeculae (n = 6) and exerted only a moderate concentration-dependent positive inotropic effect in ventricular trabeculae (approximately 25% of the response to 10(-5) M noradrenaline, n = 10). These data indicate that human alpha-CGRP caused arteriolar dilatation together with a fall in blood pressure in the pig. The tachycardia may be reflex-mediated, but the peptide also exerts a moderate positive inotropic action on ventricular trabeculae. The fall in systemic arterial blood pressure and the marked increase in capillary blood flow most likely prevented the opening of arteriovenous anastomoses. Furthermore, the antimigraine drugs, dihydroergotamine and sumatriptan, were able to reverse blood flow changes induced by human alpha-CGRP in the porcine carotid circulation.

Inhibition of endothelial nitric oxide synthase by cytochrome P-450 reductase inhibitors

Nitric oxide synthase (NOS) shows similarities to cytochrome P-450 reductase. The two enzymes catalyze the oxidation of N-omega-hydroxy-L-arginine by NADPH and oxygen to nitric oxide (NO) and citrulline. Nitric oxide synthase activity is inhibited by L-arginine analogs like N-omega-nitro-L-arginine, which does not affect cytochrome P-450 reductase. Dihydroergotamine, miconazole, and troleandomycin are classical inhibitors of cytochrome. The present study shows the concentration-dependent inhibitory effect of these compounds and of L- but not D-N-omega-nitro-arginine on the activity of constitutive nitric oxide synthase from bovine aortic endothelial cells. Activity of nitric oxide synthase was estimated by measurement of conversion of [3H]arginine to [3H]citrulline. The tested cytochrome P-450 inhibitors are likely to interfere with heme of nitric oxide synthase. The data confirms a similarity as well as functional differences between the enzymes.

Efficacy, safety, and tolerability of dihydroergotamine nasal spray as monotherapy in the treatment of acute migraine. Dihydroergotamine Nasal Spray Multicenter Investigators

Recently, a new nasal spray formulation of dihydroergotamine was developed which facilitates at-home treatment of migraine. We studied the efficacy, safety, and tolerability of dihydroergotamine nasal spray as monotherapy in the acute treatment of classic and common migraine in two, identical, double-blind, randomized, placebo-controlled trials. Of the 229 patients enrolled, 206 (102 dihydroergotamine nasal spray, 104 placebo) were included in the intent-to-treat analyses; 182 treated two headaches and 24 treated one headache. Based on both the patients' and physicians' ratings, dihydroergotamine nasal spray was significantly superior to placebo for reducing the severity of headache pain in both studies, and in relieving nausea in Study 2. The onset of significant efficacy with dihydroergotamine nasal spray compared to that with placebo for both severity of headache pain and relief of nausea occurred at 1 hour in Study 2 and at 3 hours in Study 1. Dihydroergotamine nasal spray was also significantly superior to placebo for the relief of headache pain in both studies. Based on the physicians' global evaluations of treatment efficacy for headache pain, 71% of the dihydroergotamine-treated patients in Study 2 and 59% of their counterparts in Study 1 were considered to be responders. The dihydroergotamine-treated patients had less newly-occurring vomiting than the placebo-treated patients. The majority of adverse events reported by the dihydroergotamine-treated patients were nasopharyngeal. The results demonstrate the efficacy, safety, and tolerability of dihydroergotamine nasal spray as monotherapy in the treatment of acute migraine attacks.

Blockade of noradrenaline-induced constrictions by yohimbine and prazosin differs between consecutive segments of cutaneous arteries in guinea-pig ears

1. The study has examined the receptors mediating constriction produced by brief local application of noradrenaline (NA) to cutaneous arteries and arterioles in the ear vasculature of anaesthetized guinea-pigs. The innervation of the corresponding vascular segments has been examined immunohistochemically at the conclusion of the pharmacological experiments. 2. Small arteries of branch order 4 (4 degrees, 40-110 microns internal diameter) were more sensitive to the vasoconstrictor action of NA than were more proximal arteries of branch order 3 (3 degrees, 60-150 microns internal diameter), or more distal arteries and arterioles of branch orders 5 to 7 (5 degrees-7 degrees, 18-85 microns internal diameter). This higher sensitivity of 4 degrees arteries was maintained after blockade of neuronal uptake with desipramine (1 microM), and after blockade of beta-adrenoceptors with propranolol (1 microM). 3. NA-induced vasoconstrictions of distal arterioles (5 degrees-7 degrees) were abolished or greatly reduced by yohimbine (1 microM). The blockade by yohimbine decreased progressively with increasing vessel diameter of proximal arteries, while the blockade by prazosin (1 microM) increased progressively in arteries > 40 microns diameter. 4. In 3 degrees and 4 degrees arteries, a substantial component (approximately 50%) of NA-induced vasoconstrictions remained after combined treatment with yohimbine and prazosin, in the presence or absence of desipramine. These constrictions were not further reduced by benextramine (1-10 microM), but were abolished by dihydroergotamine (1-10 microM). Constrictions induced by ATP (0.1-1 mM) were not affected by dihydroergotamine. 5. 5-Hydroxytryptamine (3-100 microM) had a variable effect on 3 degree and 4 degree arteries including: concentration dependent constrictions (n = 3); small constrictions at some concentrations, and dilatations or no change in diameter at other concentrations (n = 6); concentration-dependent dilatations only (n = 3). The 5-HT2 receptor antagonist, ketanserin (0.1-0.3 micro M), did not affect NA-induced constrictions.6. In 16 arterial segments ranging from 3 degree arteries to 60 arterioles, there was a significant correlation between the presence of neuropeptide Y-immunoreactive (NPY-IR) sympathetic axons and the degree of blockade of NA-induced constrictions by yohimbine, prazosin and dihydroergotamine.7. These results demonstrate marked differences in the postsynaptic adrenoceptors mediating vasoconstriction to a bolus of NA applied briefly to the adventitial surface of different segments of the cutaneous vasculature of the guinea-pig ear. Furthermore, the presence or absence of adrenoceptors sensitive to blockade by yohimbine or prazosin is related to the proportion of sympathetic axons innervating each vascular segment which contain NPY-IR.

Pharmacological differentiation of human 5-HT1B and 5-HT1D receptors

Human 5-hydroxytryptamine1B (5-HT1B; also designated 5-HT1D beta) receptors and 5-HT1D (also designated 5-HT1D alpha) receptors are distinct molecular entities which mediate serotonergic neurotransmission. The often confusing variability in nomenclature for these two G protein-coupled receptors derives from a preliminary observation that these receptors display nearly indistinguishable pharmacological properties. The present study analyzed a series of 21 drugs, 8 of which were found to be at least an order of magnitude more potent at 5-HT1D than 5-HT1B receptors. These data provide pharmacological evidence that human 5-HT1B and 5-HT1D receptors are distinct molecular entities which represent independent targets for future drug development. Furthermore, these data indicate that a number of selective pharmacological agents already exist and can be used to analyze the functional roles of 5-HT1B and 5-HT1D receptors.

Cardiovascular effects of KRN2391, nitroglycerin and cromakalim in dihydroergotamine-treated pithed rats

1. The effects of KRN2391 on the cardiovascular system were compared with those of nitroglycerin and cromakalim in pithed rats treated with dihydroergotamine (DHE) in order to examine the effects of these drugs on venous blood vessels. 2. DHE (100 micrograms/kg, i.v.) produced increases in mean blood pressure (MBP), cardiac output (CO) and central venous pressure (CVP) without changes in total peripheral vascular resistance (TPR) and heart rate (HR) based on venoconstriction. The DHE-treated pithed rats, nitroglycerin (30 micrograms/kg, i.v.) decreased CO and CVP whereas cromakalim (30 micrograms/kg, i.v.) produced a slight increase in CO followed by a decrease and did not affect CVP. KRN2391 (30 micrograms/kg, i.v.) produced a decrease in CVP without affecting CO. Decreases in MBP and TPR were induced by all drugs. 3. These results suggest that nitroglycerin acts predominantly as a venodilator and KRN2391 and cromakalim showed a venodilating action in addition to an arterial dilating action in DHE treated pithed rats. However, the venodilating action of KRN2391 in this condition is more potent than that of cromakalim.

Anti-migraine compounds fail to modulate the propagation of cortical spreading depression in the cat

Leao's cortical spreading depression (SD) is often cited as the pathophysiological substrate for the neurological symptoms of migraine with aura. If this is the case it might be expected that drugs useful as anti-migraine agents, particularly those useful in prophylaxis, may alter or prevent SD. Indeep it has been suggested that the anti-migraine compound dihydroergotamine (DHE) blocks or reduces the speed of propagation of SD in the rabbit. In this study we attempted to further investigate the effects of DHE and other anti-migraine drugs on SD by measuring cortical blood flow with laser Doppler flowmetry (CBFLDF) and cortical single unit activity in the alpha-chloralose-anaesthetised cat. The following substances were tested: DHE, acetylsalicylic acid, lignocaine, metoprolol, clonazepam and valproate. The NMDA-receptor blocker MK-801 and halothane (1.5%) were used as reference substances that reliably block SD. The outcome measures were speed of propagation of the wave of SD across the cortex and the CBFLDF increase during the hyperaemic phase of SD. Data were taken from three control episodes (60 min apart) and after drug administration. The rate of propagation was significantly reduced from the first control period (3.0 +/- 0.3 mm/min) to the subsequent 2 control observations (2.3 +/- 0.1 mm/min) even without any drug treatment. Following the control observations the test drug was administered and a further SD elicited. This fourth SD was reliably blocked by MK-801 and halothane. None of the other test drugs inhibited SD, reduced the rate of propagation or changed the amplitude of the CBFLDF increase.(ABSTRACT TRUNCATED AT 250 WORDS)

[The adrenergic regulation of interleukin production by bone marrow cells during immobilization stress]

Adrenergic regulation of interleukin-1 (IL-1) and interleukin-3 (IL-3) activities production by adhesive and nonadhesive bone marrow cells under immobilization stress has been studied in experiments on F1 (CBA x C57Bl/6) mice. 10-hour immobilization had been established to lead to rise of IL-1 and IL-3 activities in supernatants on days 2, 5 and 1, 2, 4, 5, 7 after stress, respectively. The use of Wilcoxon rank T-test demonstrated that alpha-adrenergic antagonist (dihydroergotaminum, 3.9 mg/kg) injection to stressed mice suppressed exclusively IL-1 activities production. At the same time, beta-adrenoblocker (propranolol, 5 mg/kg) inhibited IL-3 production. Thus, adrenergic structures take an active part in regulation of IL-1 and IL-3 production by haemopoiesis inducing microenvironment bone marrow cells under immobilization stress.

Acute and prophylactic treatment of migraine: practical approaches and pharmacologic rationale

The antimigraine efficacy of many drugs may be mediated less through their primary modes of action than through the common pathway of serotonergic transmission stabilization. Migraine treatment may be symptomatic, acute/abortive, or prophylactic. Because oral drug absorption is impaired during attacks, parenteral agents are more appropriate for acute therapy. Acute agents include ergots and ergotamine derivatives, narcotics, and sumatriptan succinate. Agents that activate the 5-HT3 receptors must be administered with an antiemetic. Sumatriptan succinate, a specific 5-HT1 receptor agonist, does not necessitate adjunctive antiemetics. Stabilization regimens, such as those using valproate, may favorably alter the natural history of migraine. Sumatriptan succinate is appropriate both for acute attacks and for symptomatic management during stabilization. beta-Blockers, tricyclic antidepressants, and calcium antagonists may be used prophylactically.

Effect of dihydroergotamine on leg blood flow during combined epidural and general anaesthesia and postoperative deep vein thrombosis after cholecystectomy

The effects of dihydroergotamine (DHE) on the circulation of the leg during combined epidural and general anaesthesia were studied to determine if DHE would enhance leg blood flow and prevent postoperative deep vein thrombosis in a double-blind trial of 40 elderly female patients subjected to cholecystectomy. Central and big toe temperature, arterial blood pressure, heart rate, calf volume and arterial inflow of the leg by electrical impedance plethysmography and the venous outflow by Doppler method were measured. DHE 0.5 mg subcutaneously reduced the volume of the leg, i.e. increased the electrical impedance, probably due to venous vasoconstriction. Simultaneously the need for etilefrine hydrochloride was reduced. No significant changes in the pulsatile inflow of the leg or the outflow were detected. Deep vein thrombosis (DVT) was detected by fibrinogen uptake test in five patients (three in DHEH and two in the control group) and verified by ascending phlebography in four patients. Intraoperative characteristics in patients with postoperative DVT were tachycardia (P < 0.001), enhanced need for etilefrine (P < 0.01) and a more rapid increase in big toe temperature (P < 0.05) after induction of epidural analgesia, compared with patients without DVT. Femoral vein flow velocity remained at the preinduction level, whereas pulsatile arterial inflow slightly increased. Together with a low basal impendance of the leg, the changes were indicative of a more intense vasodilatation, probably leading to stagnant flow and development of postoperative deep vein thrombosis.