Biomedical subjects
B P Hilton
Publications and source records attributed to B P Hilton.
The effects of reserpine injection on methysergide treated control and migrainous subjects.
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Effects of ergotamine and methysergide on blood platelet aggregation responses of migrainous subjects.
Platelet aggregation responses to 5-hydroxytryptamine (5-HT) were measured in plasma from migrainous subjects taking either methysergide maleate or ergotamine tartrate and were found to be reduced. Blood 5-HT levels of subjects free of headache were not affected by these drugs. The results support the hypothesis that methysergide and ergotamine act by occupying 5-HT uptake sites in vessel walls, leaving 5-HT molecules available to occupy receptors concerned with vasoconstriction.
Effects of reserpine and chlorpromazine on 5-hydroxytryptamine uptake of platelets from migrainous and control subjects.
Platelet aggregation experiments confirm differences between the 5-hydroxytryptamine (5-HT) receptors of migrainous and control platelets. However, no differences have been found in 5-HT uptake, in the presence of reserpine or chlorpromazine, into migrainous and control platelets. The results support the hypothesis that receptors for 5-HT induced platelet aggregation provide a model for vascular receptors causing constriction and are distinct from those transferring 5-HT through the platelet membrane.
5-Hydroxytryptamine levels and platelet aggregation responses in subjects with acute migraine headache.
Blood 5-hydroxytryptamine levels were reduced during migraine attacks in patients who had not taken any drugs but the aggregation responses to 5-hydroxytryptamine of the blood platelets from these patients were similar to responses of platelets from migrainous subjects between attacks. This confirms earlier findings that a permanent difference exists in the behaviour of platelets from migrainous subjects. Blood 5-hydroxytryptamine levels were reduced during migraine attacks in patients who had taken ergotamine. The aggregation responses of platelets taken from migrainous patients on ergotamine both during and between attacks were inhibited, which is in agreement with results previously found for aggregation responses following the in vitro pre-incubation of control platelets with ergotamine. Blood 5-hydroxytryptamine levels were maintained during migraine attacks in patients who had taken analgesics and there was no reduction in the aggregation responses of their platelets.
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.