Effects of lithium and rubidium on antinociception and behaviour in mice. I. Studies on narcotic analgesics and antagonists.

The effects of acute and chronic LiCl and RbCl treatments on the antinociception caused by morphine, pethidine, methadone, pentazocine, nalorphine or naloxone were studied in mice using the hot plate and phenylquinone writhing tests. In both tests morphine, pethidine, and methadone caused significant antinociception whereas the antagonistic drugs were almost inactive. In the hot plate test both the 21 day administration of LiCl and the 5 and 21 day administration of RbCl decreased the antinociceptive effect of morphine. The 5 day administration of LiCl increased the antinociceptive effect of pethidine whereas the acute and 5 day administrations of RbCl abolished it. There were no significant or consistent interactions of the ions with the antinociceptive effect of methadone or the antagonistic drugs. In the phenylquinone writhing test the effects of the ions were inconsistent. Especially in the acute experiments where LiCl and RbCl had some effects on the behaviour of the mice treated with the analgesics, LiCl mostly impaired motor coordination and motor activity whereas RbCl was inactive or had opposite effects. LiCl enhanced the decrease in rectal temperature whereas RbCl was mostly inactive.