Lithium dissociates haloperidol-induced behavioral supersensitivity from reduced dopac increase in rat striatum

Lithium in combination with perphenazine: effect on plasma monoamine metabolites

The addition of lithium to perphenazine altered the pattern of plasma homovanillic acid (HVA) during the course of treatment for acute psychosis. In the perphenazine-treated group plasma HVA declined significantly by days 7-9 of treatment, whereas in the perphenazine-plus-lithium group plasma HVA tended to increase. The pattern for plasma methoxyhydroxyphenethyl-glycol (MHPG) was not significantly different for the two groups. The addition of lithium to a neuroleptic may enhance the metabolism of dopamine.

A review of the biochemical and neuropharmacological actions of lithium

The pharmacological actions central to the therapeutic effects of lithium have not yet been established, despite almost 40 years of clinical use and scientific investigation. We review the biochemical and neuropharmacological data relating to this problem and attempt to identify profitable areas for further research.

Lithium attenuates the development of lesion-induced behavioral supersensitivity to apomorphine

The unilateral nigrostriatal lesion preparation was used to examine the effect of long-term treatment with lithium on rotation in response to the dopamine agonists apomorphine and amphetamine. Rats with unilateral striatal denervation received daily injections of either lithium chloride or saline for 14 days, beginning 24 h after surgery. Rats treated with lithium showed a reversible reduction in apomorphine-induced contralateral rotation. Lithium treatment failed to substantially alter amphetamine-induced ipsilateral rotation. When treatment was initiated 14 days after surgery, rats treated with lithium showed no reduction in apomorphine-induced contralateral rotation. These findings suggest that lithium attenuates the development of lesion-induced behavioral supersensitivity but fails to alter supersensitivity which has developed previously.

Lithium does not interact with haloperidol in the dopaminergic pathways of the rat brain

Prophylactic treatment with lithium has been reported to prevent haloperidol-induced dopamine (DA) receptor supersensitivity. If such an effect exists, then lithium may be useful in the prevention of tardive dyskinesia, which is related to the neuroleptic-induced DA hyperfunction. In the experiments reported here chronic lithium administration had no effect on DA synthesis or utilization in the nigrostriatal, mesolimbic, or mesocortical DA pathways in the rat brain. Similarly, lithium had no effect on the increase in DA metabolism induced by the acute administration of haloperidol. Also, chronic lithium treatment failed to modify the biochemical tolerance which developed after prolonged administration of the neuroleptic drug. Supersensitivity of the presynaptic DA receptors, which was induced by prolonged exposure to haloperidol, likewise was unaffected by prophylactic lithium treatment. We conclude that lithium does not affect changes in DA metabolism or receptor supersensitivity induced by haloperidol. These results do not support the use of lithium in neurological disorders that may be related to neuroleptic-induced DA receptor supersensitivity.

The effects of chronic lithium on behavioral and biochemical indices of dopamine receptor supersensitivity in the rat

The effects of dietary lithium on several indices of dopamine receptor supersensitivity were examined in rats during withdrawal from chronic administration of haloperidol. Chronic haloperidol enhanced the locomotor stimulant action of d-amphetamine, and this effect was attenuated by lithium. In contrast, lithium did not affect the amphetamine response in animals that had not previously received haloperidol. Apomorphine-induced hypothermia was not influenced by the chronic haloperidol treatment. On the other hand, during withdrawal from chronic haloperidol, spontaneous locomotor activity (20 h) and apomorphine-induced stereotypy were increased, but neither of these effects was attenuated by lithium. In addition, lithium did not affect the chronic haloperidol-induced increase in 3H-spiperone binding sites in the striatum. Lithium alone had no effect on any of these measures except for causing a slight prolongation of the hypothermic effect of apomorphine. The results indicate that not all DA-receptor-mediated responses are enhanced by chronic administration of neuroleptics (e.g., apomorphine-induced hypothermia). In addition, while lithium reduces the effects of chronic haloperidol administration on d-amphetamine-induced locomotor activity, this is not because lithium prevents haloperidol-induced supersensitivity of postsynaptic DA receptors because more direct measures of this phenomenon (e.g., 3H-spiperone binding, apomorphine-induced stereotypy) are not affected by lithium.

Influence of lithium on biochemical manifestations of striatal dopamine target cell supersensitivity induced by prolonged haloperidol treatment

The effects of prolonged treatment with dietary lithium and/or haloperidol (infused by means of osmotic minipumps) on biochemical parameters indicative of striatal dopamine target cell supersensitivity have been investigated in the rat. When given concomitantly with haloperidol, lithium failed to prevent the fall of striatal dopamine metabolites observed 2 days following withdrawal and the tolerance to the elevation of dopamine metabolites in response to challenge with the neuroleptic during withdrawal. Prolonged treatment with lithium also failed to modify the changes in nigral dihydroxyphenylacetic acid levels and in striatal acetylcholine levels which occur under chronic neuroleptic treatment. Chronic dietary lithium alone consistently elevated substance P levels in substantia nigra. The usual decrease in nigral levels of the peptide that occurs in response to chronic treatment with haloperidol was prevented in animals treated concomitantly with lithium. These data suggest that the mechanism whereby lithium stabilizes dopaminergic supersensitivity does not seem to involve an action of the compound on the neuronal mechanisms regulating the activity of the nigro-striatal dopaminergic system or on striatal cholinergic neurons but may be related to the restoration of normal striato-nigral substance P ergic transmission.