Effects on Central Dopaminergic Systems of d-Coclaurine and d-Reticuline, extracted from Magnolia salicifolia

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Abstract
The present investigation was undertaken to study effects of benzyltetrahydro-isoquinoline alkaloids, d-coclaurine and d-reticuline, extracted from dried flower buds of Magnolia salicifolia MAX. on gross behavioural parameters following intracerebroventricular administration in mice and on dopamine uptake in the mouse iris. d-Coclaurine 25 µg produced an inhibition of locomotor activity, ptosis and catalepsy. One hour after injection it produced stereotyped behaviour, such as sniffing and gnawing. Pretreatment with d-coclaurine 25 µg suppressed locomotor activation and rotational behaviour induced by apomorphine and methamphetamine. d-Reticuline 100 µg produced catalepsy and a decrease in locomotor activity. d-Reticuline blocked locomotor activation and rotational behaviour induced by apomorphine, but not those induced by methamphetamine. 1-N-Methylcoclaurine 25 µg produced muscular twitch and tremor. It produced clonic convulsions at the dose of 100 µg. d-Coclaurine 20 mg/kg, i.v. suppressed dopamine uptake in the mouse iris pre-treated with alpha-methyl-p-tyrosine. It is indicated that d-coclaurine has a neuroleptic-like property in blocking effects of dopaminergic stimulating agents, but this does not necessarily explain inhibition of dopamine uptake in the mouse iris. Mode of action of d-reticuline may be different from that of d-coclaurine.