Direct Dopaminergic Action of Lisuride Hydrogen Maleate, an Ergot Derivative, in Mice

Lisuride hydrogen maleate induced stereotyped behaviour in normal as well as in reserpinized mice. It antagonized the motor depression and hypothermia induced by reserpine. On i.p. administration the compound was about as effective as apomorphine and D-amphetamine. As with apomorphine and in contrast to D-amphetamine the effects of lisuride hydrogen maleate in reserpinized mice were not impaired by additional treatment with alpha-methyl-p-tyrosine methylester. In untreated mice, the substance was very potent in lowering body temperature with significant hypothermia measured after dosages as low as 0.10 mg/kg i.p. Occurrence of stereotyped behaviour and hypothermia could be prevented by the dopaminergic antagonist haloperidol. From these data it is concluded that lisuride hydrogen maleate in addition to its interaction with serotoninergic systems is a potent dopaminergic agonist with a probably direct action on dopaminergic receptors. Further arguments in support of such an action of lisuride hydrogen maleate are, in addition to biochemical data, its serum prolactin lowering effect in rats, its strong emetic action in dogs and its effects on rat behaviour.