Role of sodium cromoglycate on analgesia, locomotor activity and opiate withdrawal in mice.

The role of sodium cromoglycate (CRO) on analgesia, locomotor activity and morphine withdrawal in mice was studied in morphine-dependent and drug-naive mice. CRO (0.5, 1, 5, 10, 30, 50 and 100 mg/kg, SC) induces analgesia (hot plate), an effect blocked by previous administration of the opiate antagonist naloxone (1 mg/kg). Furthermore, CRO (30 mg/kg) potentiates morphine analgesia. In morphine-tolerant mice, moderate doses of CRO (0.5, 1, 5, 10 and 30 mg/kg) do not induce analgesia, which suggested the development of cross tolerance between CRO and morphine, whereas coadministration of CRO and morphine in morphine tolerant animals restored the sensitivity to morphine. Administration of CRO (10 and 30 mg/kg) induces an increase in spontaneous locomotor activity, and previous administration of naloxone (1 mg/kg) blocks this effect, whereas CRO (10 mg/kg) blocks morphine (10 mg/kg) and amphetamine (3 mg/kg)-induced hyperactivity. CRO (10, 50 and 100 mg/kg) induces a significant and dose-dependent reduction in the number of jumps ("jumping up") during naloxone (1 mg/kg)-induced withdrawal in morphine-dependent mice. Finally, CRO (100 mg/kg) reduces the "wet dog shake" phenomenom during naloxone-induced withdrawal in morphine-dependent mice. These results suggest a possible stabilizing effect of CRO on the membranes of neurones that mediate analgesia, locomotor activity and opiate abstinence. Changes and inhibition of DA, NA and 5-HT release may also explain these effects.