Apomorphine in low dosage (0.3 mg/kg) inhibits climbing behavior, a stereotyped motor activity, in mice. Pretreatment with apomorphine in low doses (0.125 or 0.25 mg/kg) or with piribedil (25 mg/kg), a weak dopamine agonist, results in a less marked inhibitory effect of the test dose of apomorphine. Apomorphine in low dosage or piribedil are also able to… (More)
Mice treated with apomorphine tend to adopt a vertical position in a stereotyped manner. A quantal evaluation of this behaviour, taking into account its frequency and duration, leads to a biphasic dose-response curve that reveals opposite actions of the dopamine agonist.
In the mouse 'behavioral despair' test the immobility time was shortened by [D-Ala2,Met5]enkephalin at doses which did not modify locomotor activity. Similarly, the inhibitors of the enzymes degrading enkephalins, thiorphan and/or bestatin were effective. Their effect was antagonized by naloxone. We conclude that endogenous enkephalins are implicated in the… (More)
The climbing behaviour, a stereotyped motor behaviour, is elicited in mice by stimulation of striatal dopamine receptor by low doses of apomorphine. The action of apomorphine is unexpectedly enhanced in animals pretreated with a single dose of this agent (5 mg/kg). This enhancement occurs as early as 2 h following the first administration and persists for… (More)
The sensitivity of dopamine receptors in Mouse striatum has been evaluated both behaviourally (responsiveness to apomorphine as regarviour) and biochemically (striatal level of homovanillic acid and its decrease induced by apomorphine) After a single administration of apomorphine (0.25 mg.kg-1 or 5 mg.kg-1) or piribedil, another dopamine agonist, a state of… (More)