Haloperidol attenuation of morphine abstinence: synergistic effect of acute lithium administration

The role of dopamine in the expression of morphine withdrawal

1. Both L-dopa and low doses of apomorphine potentiated withdrawal symptoms such as jumping, "wet dog" shakes and burrows. L-dopa reduced hypothermia and potentiated body weight loss, whereas apomorphine produced opposite effects. 2. Higher doses of apomorphine attenuated jumping and burrows but had no effect on "wet dog" shakes. On the other hand, and with the exception of sulpiride, all other dopamine (DA) antagonists produced effects opposite those of the agonists with regard to jumping, "wet dog" shakes and burrows. 3. In addition, DA antagonists reduced hypothermia and body weight loss. The effects of DA agonists and antagonists were investigated in mice injected with 6-hydroxydopamine (6-OHDA) intracerebrally to examine whether DA-mediated effects are somehow linked to noradrenergic pathways. 4. Mice pretreated with 6-OHDA developed a higher degree of naloxone-induced withdrawal jumping than did untreated mice. 6-OHDA reversed the effects of apomorphine on "wet dog" shakes and burrows while abolishing those of L-dopa on all withdrawal symptoms, the only exception being jumping, which remained unchanged. 5. 6-OHDA also reversed the effects of sulpiride on all withdrawal symptoms while reversing the effects of pimozide on jumping, and it abolished its effect on hypothermia. 6. These findings provide evidence suggesting that the effects of DA agonists and antagonists are dependent at least partly on intact noradrenergic pathways.

The attenuation of delta 9-tetrahydrocannabinol and morphine of the quasi-morphine withdrawal syndrome in rats

The effect of delta 9-tetrahydrocannabinol (THC), morphine, haloperidol and chlordiazepoxide on the exhibition of the signs of the quasi-morphine withdrawal syndrome was studied in rats. In preliminary studies approximately equi-sedative doses of these drugs were chosen. Morphine and THC produced a very similar degree of suppression of the signs of the quasi-morphine withdrawal, but unlike morphine, the effects of THC were not reversed by the narcotic antagonist, naloxone. The dopamine receptor antagonist, haloperidol, produced a moderate suppression of the withdrawal syndrome and chlordiazepoxide was without significant effect. It is concluded that THC is of very similar potency to morphine in suppressing the quasi-morphine withdrawal syndrome, but its activity in this regard does not appear to be dependent upon the availability of opiate or dopamine receptors, nor is it due to sedation alone.

Enhanced naloxone potency and the development of narcotic tolerance

When various biogenic amine modifying drugs were administered to mice which were pretreated with morphine, none of the drugs except atropine and haloperidol altered the usual doubling of the naloxone efficacy which is observed in morphine-pretreated mice. Atropine appeared to decrease the potency of naloxone. Haloperidol, which did not alter naloxone potency in normal mice, further increased the naloxone potency in morphine-pretreated mice. When the biogenic amine modifiers were injected chronically to mice during the development of morphine tolerance, again none of the drugs, except haloperidol and atropine altered the development of tolerance. Haloperidol appeared to enhance and atropine to inhibit the degree of tolerance. These results indicate that it is the alteration in the narcotic-induced enhancement of naloxone potency and not the mere alteration of noloxone potency by various drugs, which can be used as an indicator of the alterations in the development of tolerance.