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Stone TW. 
“Further evidence for a dopomine receptor stimulating action of an ergot alkaloid”. 
Brain Research. 1974;72:177-180.
Several recent reports have suggested that some, at least, of the group of alkaloids present in ergot (Clariceps purpurea) may have a potent stimulating action on dopamine receptors in the mammalian central nervous system, and that this effect could contribute to the marked behavioural effects produced by them. One of these reports concerned the alkaloid agroclavine which was shown to induce stereotyped sniffing and gnawing behaviour in rats at the low dose of 1-2 mg/kg, s.c.. Such induced stereotypy is usually considered indicative of an activation of central dopamine receptors. The present series of experiments was therefore designed to examine the effects of agroclavine directly on central neurones in order to try and obtain more direct evidence for such an action. Unit responses to agroclavine have been compared with responses to dopamine, noradrenaline and 5-hydroxytryptamine and attempts have been made to antagonise these responses. All experiments were performed on male rats-weighing 250-300 g and anaesthetised with urethane 1.25 g/kg, i.p. Conventional microiontophoresis techniques were used as described in detail elsewhere to apply drugs to spontaneously active randomly encountered cells in the parietal cerebral cortex. One barrel of the 5-barrelled micropipettes was filled with a 200 mM solution of agroclavine (base) made in distilled water containing either 1.5 mM tartaric'acid or 200 mM ascorbic acid. The pH of the resulting solution was approximately 4.0. One barrel also contained a solution-of tartaric or ascorbic acid at pH 4:0 as a control of H+ effects. A third barrel contained 200 mM sodium chloride at pH 4.0 for current balancings and checking current effects. The remaining barrels were filled with solutions of either 200 mM dopamine hydrochloride, pH 4.0;'200 mM ()noradrenaline bitartrate, pH 4.0; 50 mM 5 - hydroxytryptamine creatinine sulphate, pH 4.5; or 200 mM chlorpromazine hydro - chloride, pH 4.0. Recording of cell activity was achieved through a single micropipette containing I M potassium acetate attached to the multibarrel assembly via an Ekco instantaneous ratemeter onto a Servoscribe pen recorder.
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