Plasma serotonin in migraine and stress

Morphine abstinence and serotonin supersensitivity in man: analogies with the mechanism of migraine?

Supersensitivity to serotonin during migraine attack has been previously observed. Since the attack has been attributed to a critical lowering of morphine-like factors, we can expect serotonin supersensitivity during morphine abstinence. Slight signs of morphine abstinence have also been induced in volunteers after mild (10-24 mg/day) and limited (3 days) treatment. To evaluate the sensitivity to serotonin, dopamine, noradrenaline, and tyramine in the smooth muscle of the hand dorsal vein, in vivo, the computerized venotest was applied before, during, and 24 h after withdrawal of morphine. Venous sensitivity to serotonin and dopamine (but not to noradrenaline and tyramine) increased 10- to 20-fold after morphine withdrawal. Venous monoamine supersensitivity in morphine abstinence, similar to that observed during migraine attacks, could be indirect evidence of an analogous mechanism in both conditions.

Migraine: A blood disorder?

It is suggested that a primary abnormality of platelet function can account for the diverse clinical, biochemical, and pathological findings reported in migraine.

The effect of intracarotid infusion of dexamethasone and 5-hydroxytryptamine on cerebral blood flow and metabolism in baboons

The effect of intracarotid infusion of dexamethasone on cerebral blood flow and cerebral oxygen utilization was measured in baboons using the xenon-133 clearance technique. The cerebrovascular response to intracarotid infusion of 5-hydroxytryptamine (5-ht) was then determined during simultaneous infusion of the steroid. Infusion of dexamethasone alone and infusion with 5-HT produced no significant change in cerebral blood flow or cerebral oxygen utilization when compared to baseline values. The study indicates that neither dexamethasone nor 5-HT with dexamethasone modify cerebral blood flow when infused via the internal carotid artery.

A basis for migraine therapy- the autonomic theory reappraised

The concept that migraine results from an initial vasoconstriction due to increased release of noradrenaline from the sympathetic nerves to cranial blood vessels has been reappraised in the light of recently acquired knowledge of the mechanisms of action of drugs used in the treatment of migraine, physiological and pharmacological evidence implicating noradrenaline, and the observations by others that several migraine variants may be associated with some degree of sympathetic overactivity. If the theory is correct, it suggests that both prophylaxis and management of the acute condition should be possible by means of selective alpha-adrenoceptor antagonism. The use of drugs with potentially dangerous vasoconstrictor properties appears to be unnecessary. The suggestion is made that the increased adrenergic activity might result from changes within the hypothalamus.

Migraine and the blood-brain barrier

The prodromal (cerebral) symptoms of migraine are associated with a fall in cerebral blood-flow (C.B.F.). The suggestion that various circulating vasoactive agents might be the cause of this fall in C.B.F. ignores the contradictory findings that the cerebral vascular bed is normally unresponsive to such agents; but if the blood-barrier is disrupted, systemically administered monoamines and prostaglandins elicit pronounced changes in cerebral-tissue perfusion and metabolism. A defect in the blood-brain barrier of migraine patients (particularly those in whom an item of diet may trigger an attack) would make the cerebral circulation vulnerable to variations in circulating levels of vasoactive substances. Alternatively, the barrier could be intact in non-dietary patients, but release of monoamines or prostaglandins from the brain itself could account for the observed changes in the cerebral circulation.

Cerebrovascular response to infused 5-hydroxytryptamine in the baboon. Part 1. 5-Hydroxytryptamine infusion

Cerebral blood flow was measured in 17 baboons before and during infusion of 5-hydroxytryptamine (5-HT) into the internal carotid artery. The mean values for total cerebral blood flow, grey matter flow, and white matter flow before 5-HT infusion were 40.8, 59.2, and 12.7 ml/min/100 gm of tissue, respectively. There was no significant alteration in total blood flow or flow through grey matter when 5-HT was infused at dosages ranging from 0.5 to 10.0 microng/kg/min. A small but significant decrease in white matter blood flow was recorded when 5-HT was infused at a rate exceeding 2.5 microng/kg/min. The study indicates that in vivo, with the xenon clearance method, intra-arterial infusion of 5-HT does not significantly alter cerebral blood flow.

Cerebrovascular response to infused 5-hydroxytryptamine in the baboon. Part 2. 5 Hydroxytryptamine infusion in estrogen and progesterone treated animals

The effect of intracarotid infusion of 5-hydroxytryptamine (5-HT) on cerebral blood flow was studied in five female baboons 7 days after intramuscular injection of slow release estrogen and progesterone. The control values for total cerebral blood flow, grey matter flow, and white matter flow were 38.9, 57.5, and 11.0 ml/min/100 gm of tissue respectively. There was a statistically significant decrease in total, grey and white matter blood flow during infusion of 5-HT at dosages ranging from 0.5 to 10.0 microng/kg/min. The study indicates that in female baboons pretreated with estrogen and progesterone, intracarotid infusion of 5-HT produces a dose dependent decrease in cerebral blood flow, which did not occur in control animals.

Transitory decrease in platelet monoamine-oxidase activity during migraine attacks

A highly significant decrease in platelet monoamine-oxidase activity has been observed in migrainous subjects during a migraine attack compared with activity outside an attack. The effect did not derive from drugs commonly used in migraine therapy.

Total 5-hydroxyindoles in blood related to migraine attacks

The total 5-hydroxyindoles (5HI) in whole blood were measured in 20 migraine patients during spontaneous migraine attacks and in headache-free periods. A statistically significant fall in blood 5-HI was found during headache in 17 patients suffering from classical and common migraine. In one patient with complicated migraine no change was found, and in two patients, one with common migraine and one with migraine and associated symptoms, there was a rise in total blood 5-HI during migraine attacks. The results are compared with previous findings in this field, and it is suggested that during migraine attacks there might be a rise in the plasma 5-HI. The possibility of using the 5-HI fall during spontaneous migraine attacks as a simple test for the diagnosis of migraine is discussed.

Release of platelet 5-hydroxytryptamine by plasma taken from patients during and between migraine attacks

Experiments were carried out in order to further delineate the pathophysiology of the fall of plasma 5-hydroxytryptamine (5-HT) during a migraine attack. Platelets from normal subjects were incubated with 14C-labelled 5-HT, and the release of 5-HT was measured following exposure of these platelets to plasma taken from migraine patients during an attack or at headache-free intervals. Plasma taken during attacks released significantly more 5-HT. It is concluded that factor(s) exist in the serum during migraine attacks, which can cause 5-HT release from normal platelets. The identification of this factor may be important.

Comparative effects of four migraine prophylactic drugs on an isolated extracranial artery

Clonidine and methysergide constrict the rabbit auricular artery by activating smooth muscle alpha-adrenoceptors. Clonidine inhibits and methysergide enhances responses to stimulation of the sympathetic nerves. Both drugs sensitise the artery to a variety of vasoconstrictor stimuli, although not to potassium chloride. This weak generalised sensitisation may depend on clonidine and methysergide themselves being vasoconstrictor since sensitisation after clonidine did not occur when vasoconstriction was abolished with phentolamine. The marked potentiation of 5-HT and tryptamine observed during clonidine perfusion may reflect a property of the tryptamines since it was observed during perfusion with histamine but not when histamine vasoconstriction was abolished with mepyramine. Cyproheptadine and pizotifen neither constrict the artery nor sensitise it to vasoconstrictor agents. They inhibit responses to nerve stimulation, alpha-adrenoceptor agonists, potassium chloride and particularly histamine. Sensitisation of blood vessels reinforced by direct vasoconstriction may contribute to the mechanism of action of clonidine and methysergide in migraine. Conversely, alterations in vascular function may be less important to the antimigraine actions of either cyproheptadine or pizotifen.

Responsiveness of isolated canine cerebral and peripheral arteries to ergotamine

Changes in tension of spiral strips from dog saphenous, external carotid and basilar arteries were monitored isometrically. Serotonin (5-HT) contracted the 3 arterial preparations in about the same concentration range. Compared with noradrenaline (NA) (100%) the efficacy of 5-HT was about 60% on saphenous, 150% on external carotid and about 500% on basilar arteries. Ergotamine (E) stimulated the 3 vascular preparations in concentrations about 100 times lower than 5-HT. Compared with NA the efficacy of E was about 20% on saphenous, 50% on external carotid and 200% on basilar arteries. Compared with 5-HT (100%) however, E had similar constrictor activities in the 3 arteries. It seemed likely therefore that 5-HT receptors are involved in the vasoconstrictor activity of E. Evidence for this was obtained in experiments in which cyproheptadine (Cy), a 5-HT antagonist, was used. For antagonism of E concentrations of Cy about 6 times higher than those required to inhibit 5-HT were necessary, whereas for antagonism of NA about 500 times higher Cy concentrations were necessary. The results suggest that on canine arterial vascular smooth muscle the constrictor activity of E is mediated mainly through serotoninergic receptor sites.

Migraine in children and adolescents

Although migraine has been considered in the past to be uncommon in children and adolescents, there is mounting evidence that it is not, and that it produces significant childhood morbidity. However, the clinical picture varies from case to case, and often from attack to attack in the same patient. Stress plays a most important role in triggering attacks of this familial disease, and the physician must be aware of this if his treatment is to be successful. In adolescent girls, falling estradiol plasma levels are apprently important in triggering attacks of migraine associated with menstruation. In an attack, the initial vasoconstrictive phase, mainly intracranial gives way to a vasodilative phase, mainly extracranial, which results from withdrawal of the vasoconstrictive support from the extracranial arteries which is normally provided by serotonin. The plasma level of the latter drops sharply during an attack, and its excretion product, 5-hydroxy-indole acetic acid, appears in increased amounts in the urine. Laboratory investigations, after a most careful, detailed history, and physical examination, should include an EEG, skull films and possibly a brain scan. Management includes prophylactic measures, both environmental and pharmacologic, and treatment of the attack itself, where promptness is the watchword.

The acute effects of oral (--)-tryptophan in human subjects

1 The psychotropic effects of a single oral dose of (--)-tryptophan (5 g) in human volunteers were investigated using a series of physiological and psychological tests. 2 Self-ratings of mood showed increase in drowsiness but no euphoria was detected. 3 Severe initial nausea occurred and headache increased; other bodily symptoms were unaffected. 4 Trptophan caused increased activity in the slow wavebands of the EEG but did not alter the other physiological measures. 5 The levels of total and free tryptophan in the plasma increased 8 and 20 fold respectively to peak levels 2 h after ingestion.

The significance of blood serotonin levels in migraine. A critical review

Available evidence indicates that serotonin located within platelets--or lack of it--does not precipitate migraine attacks, and that intravenously administered serotonin is beneficial in migraine. On this premise, it is not likely that the beneficial effect of intravenously administered serotonin is due to replacement of lost intracellular serotonin. If serotonin is effective in relieving migraine pain, this is probably due to extracellular serotonin acting on the cardiovascular system. In other words, serotonin-induced relief in migraine is probably caused by the pharmacological properties of the amine--it probably acts as a drug and not by replacement. The serotonin changes in migraine are probably not primary, but caused by the disease process. Platelets may nevertheless be of importance in the pathogenesis of migraine, and serotonin may be of even more interest. However, interest in platelet serotonin will probably be diminishing in the future.

The role of humoral mediators in migraine headache

The classical vascular mechanism of migraine attacks demonstrated by Wolff — intracranial vasoconstriction during the prodromal stage and passive vasodilatation of extracranial arteries during the painful phase — has been confirmed by modern methods. Arterial distension is, however, not sufficient to explain the origin of the pain: to give rise to an acute migraineous pain, it must be associated with a lowered pain threshold of the receptors situated in the wall of the affected vessels. A number of humoral factors — plasmakinin, serotonin, histamine — intervene in the chain of events that culminates in migraine headache.

At the start of the attack, the blood platelets release serotonin, the mast cells in the affected area release histamine and proteolytic enzymes that split plasmakininogens to form plas-makinins. Free serotonin and histamine increase capillary permeability and favor transudation of plasmakinin into the vessel walls andperivascular tissues. The combined effect of serotonin and plasmakinin on the vessel wall receptors reduces their pain threshold. On the other hand, the bulk of the released serotonin is excreted as 5-HIAA, and plasma serotonin falls. Since serotonin has a constricting effect on the extracranial arteries and a dilating one on the capillaries, the fall in its plasma level induces hypotonia of these arteries and capillary constriction, which results in a passive distension of the arterial walls. The two factors necessary for the production of pain are thus present: a low pain threshold and vascular distension. In addition to these three main humoral mediators, the part played by tyramine in migraine of alimentary origin, the precipitating effect of estrogen decrease in mentrual migraine and the hypothetical role of prostaglan-dins and prolactin are discussed.

Effects of methysergide on platelets incubated with reserpine

1. Platelets were incubated with methysergide and related compounds (2-bromo lysergic acid (BOL), ergotamine and methyl ergotamine) together with reserpine.2. Methysergide inhibited the normal aggregation response of platelets to 5-hydroxytryptamine (5HT) but did not affect the reduction in the 5HT content caused by reserpine, or the uptake of 5HT by the platelets.3. BOL, ergotamine and methyl ergotamine behaved similarly. Methysergide had greater anti5HT potency than BOL, and methyl ergotamine had greater potency than ergotamine.4. The use of platelets as a model for synaptic preparations is discussed.5. The role of 5HT receptor sites on the platelet membrane and the significance of the results for migraine patients treated with methysergide are discussed.

An assessment of platelet aggregation induced by 5-hydroxytryptamine

A method of expressing platelet aggregation response after incubation relative to the response before incubation has been used in preference to using direct measurements, and some reasons are given for this choice. The effect of pre-incubating human platelets with reserpine has been compared with the effect of pre-incubation with 5-hydroxytryptamine (5HT). Reserpine inhibited 5HT-induced aggregation more slowly than 5HT and on this basis their actions could be distinguished. It was found that the aggregation response of human platelets to 5HT without pre-incubation (R) is inversely proportional to the natural 5HT content of whole blood, and an explanation has been suggested.A decrease in the aggregation response of human platelets to 5HT without pre-incubation (R) with increasing age has been noted, and is commented upon with reference to the release of amines from blood platelets. Platelets in plasma obtained from control subjects and incubated with methysergide and from migrainous patients taking methysergide both have reduced aggregation responses to 5HT. Platelets incubated with clonidine (St155) do not have reduced aggregation responses. A potentiating effect was noted after 20 minutes' incubation, but platelets from migraine patients taking St155 behaved normally. Tyramine affected the response of platelets to 5HT, giving results similar to those reported for reserpine. The differences between the aggregation responses to 5HT of platelets from migraine patients and normal control subjects are discussed.

Comparative trial of serotonin antagonists in the management of migraine

The effectiveness of five different serotonin antagonists in the prevention of migraine was compared in 290 patients followed for periods of up to three years. Methysergide 3-6 mg. daily was most effective, with 20% of treated patients becoming headache-free and a further 44% remaining more than "half improved." The corresponding figures for BC105 were 10% and 40%, respectively.The results with BC105 were significantly better than those with placebo (P<0.02). The total improvement rates with methdilazine (45%) and cyproheptadine (43%) were better than those with placebo (32%) but did not achieve statistical significance. A new preparation, methylergol carbamide maleate, which is chemically related to methysergide, did not give better results than placebo.