Effects of amantadine on modification of dopamine dependent behaviours by molindone.

Amantadine, a dopamine agonist is reported to act by releasing dopamine from the dopaminergic nerve terminals as an anti-Parkinsonian drug. In the present behavioural study in the rat, molindone-induced catalepsy and ptosis, which are dopamine dependent-behaviors are reversed by amantadine. Amantadine has also revered molindone-induced inhibition of traction response in mice. Our study indicates that amantadine, like other DA agonists, e.g. amphetamine and apomorphine can antagonize or even reverse the neuroleptic induced dopaminergic behaviors.

Antagonism of bromocriptine-induced cage climbing behaviour in mice by the selective D-2 dopamine receptor antagonists, metoclopramide and molindone.

Bromocriptine (5-30 mg/kg, ip), 2 hr after administration, induced cage climbing behaviour in mice. Pretreatment with haloperidol, an antagonist of both D-1 and D-2 dopamine receptors, metoclopramide and molindone, the selective D-2 dopamine receptor antagonists, effectively antagonised bromocriptine-induced climbing behaviour. The results indicate that bromocriptine most probably induces climbing behaviour in mice by stimulating the postsynaptic striatal D-2 dopamine receptors.

Effect of alpha-methyl-p-tyrosine on neuroleptic-induced catalepsy in rat.

Pretreatment with alpha-methyl-p-tyrosine, a tyrosine hydroxylase inhibitor, was found to increase the intensity of catalepsy induced by haloperidol, chlorpromazine and molindone. The drug probably decreases the synthesis of dopamine and makes less dopamine available for release and to compete with the neuroleptic for the postsynaptic striatal dopamine receptor sites with resultant potentiation of the neuroleptic-induced catalepsy.

Effect of drugs influencing central 5-hydroxytryptamine mechanisms on amantadine-induced stereotyped behaviour in the rat.

Pretreatment with L-tryptophan, a precursor of 5-HT, was found to decrease the intensity of stereotyped behaviour induced by amantadine, while methysergide, a 5-HT antagonist, was found to increase the intensity of amantadine-induced stereotypy. These results suggest that the intensity of amantadine-induced stereotypy depends on the balance between central dopamine and 5-HT systems and that the central 5-HT systems may have an opposing, tonic effect upon central dopamine systems involved in the mediation of stereotypy. In contrast to L-tryptophan, however, pretreatment with quipazine, a 5-HT agonist, and clomipramine, a selective 5-HT neuronal reuptake blocker, was found to potentiate the stereotyped behaviour induced by amantadine.

Experimental evaluation of the antidepressant and neuroleptic activity of maprotiline.

Maprotiline, a tetracyclic antidepressant drug, was evaluated for antidepressant and neuroleptic activity. In antidepressant tests, maprotiline antagonized reserpine-induced ptosis in rats but, unlike the tricyclic antidepressants, was found to antagonize methamphetamine stereotypy in rats, to decrease the intensity of L-dopa induced behavioural syndrome in pargyline-pretreated mice and to be ineffective in intensifying the 5-HTP induced behavioural syndrome. In neuroleptic tests, maprotiline was found to, antagonize apomorphine-induced cage climbing behaviour, induce catalepsy, inhibit the CAR and traction response, decrease the spontaneous motor activity and exploratory behaviour, and to potentiate the hypnotic effect of pentobarbitone. Our results indicate that maprotiline exhibits a profile of activity which resembles the neuroleptics and most probably exerts post-synaptic striatal DA receptor blocking activity.

Blockade of the dopamine depressor response by molindone, a newly introduced neuroleptic.

Pretreatment with the neuroleptics, haloperidol and molindone, significantly antagonized the dopamine-induced depressor response in the anaesthetized dogs. The depressor response to dopamine was however, not significantly affected by propranolol, atropine or antazoline pretreatment. The results suggest that molindone like haloperidol, is capable of blocking the vascular dopamine receptors responsible for mediating dopamine-induced vasodilatation in the coeliac, mesenteric and renal vascular bed and fall in blood pressure.