The role of dopamine in the effects of pentazocine and tripelennamine.

CNS dopamine has been suggested as a mediator in the effects of many drugs of abuse. The present study was conducted to assess the potential dopaminergic activity of pentazocine and tripelennamine combinations (T's and Blues). The effects of pentazocine and tripelennamine, administered alone and in combination with several dopaminergic drugs, on milk drinking were assessed in the rat. Both the opioid and antihistamine were tested in combination with apomorphine and haloperidol. Pentazocine was also tested in combination with the D1- and D2-receptor selective antagonists SCH 23390 and raclopride, and with the D2-receptor agonist quinpirole. Tripelennamine was additionally tested in combination with methamphetamine. Haloperidol and quinpirole pretreatment produced leftward shifts in the pentazocine dose-effect curve while raclopride and SCH 23390 shifted the opioid curve to the right. Doses of apomorphine shifted tripelennamine's dose-effect curve to the left, tripelennamine enhanced the effects of methamphetamine, but haloperidol did not alter the antihistamine's effects. These data suggest dopaminergic involvement in the effects of the opioid and antihistamine.