Erowid References Database
“L'ergot de seigle: des conceptions de dale aux récepteurs”.
J.Pharmacol.. 1979;10(4 bis.):377-82.
The mechanism of the effects of ergot alkaloids at various receptors is reviewed. Although Dale himself did not support the receptor theory, the classification of alpha- and beta-adrenergic receptors has evolved from his work. Brief mention is made of structural considerations which suggest that ergot alkaloids act on adrenergic, dopaminergic and serotoninergic receptors. For comparison, the crystalline structure of ergotamine and dihydroergotamine are matched with partial chemical structures and with chemical structures of noradrenaline, dopamine and 5-HT. The relationship between these chemical structures and that of lysergic acid is mentioned. Studies are reviewed which illustrate that some actions of the ergot alkaloids are compatible with the concept of an effect on adrenergic, dopaminergic and serotoninergic receptors. Dibydroergotoxine (Hydergine) is used therapeutically in elderly patients to treat cerebral circulatory insufficiency. It may act partially on dopaminergic receptors but its antagonist effect against cerebral noradrenaline has been studied. Rat brain homogenates were incubated and effects of noradrenaline determined by formation of cAMP. Addition of small concentrations of dIhydroergotoxin to the homogenates antagonized the effects of noradrenaline. In other studies, after long-term p.o. administration to rats, dihydroergotoxine accumulated-in the brain. Contralateral rotation in rats was studied, using apomorphine as control, since this indicates stimulation of central dopaminergic receptors. Bromocriptine induced slow but prolonged stimulation of contralateral rotation. This effect is the basis of its therapeutic activity in Parkinson's disease. LSD acts on 5-HT receptors. Application by electrophoresis of LSD or 5-HT to rat brain raphe neurons inhibted electrical activation, suggesting that both substances act on 5-HT receptors. A dose of 35 mg LSD s.c. is hallucinogenic in man. Structural formulae are given for hallucinogens LSD, psilocybine, mescaline, dimethyltryptamine and DOM.
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