Effect of lithium on swim stress-induced antinociception in naive mice and mice with subchronic administration of morphine or swim stress in formalin test.

BACKGROUND Lithium has been shown to relieve mania and induce antinociception. In the present study, swim stress at 8C induced antinociception in both phases of the formalin test. Intraperitoneal administration of lithium chloride (LiCl) (0.05, 0.25, and 0.5 mg/kg) also induced antinociception in both phases of the formalin test. METHODS Antinociception was assessed by the formalin test method. Swim stress was achieved in the 8C water in a container 5 cm in diameter and 20 cm tall filled with water do a depth of 11 cm. RESULTS The drug (0.5 and 5 mg/kg) potentiated swim stress-induced antinociception in the second phase of the test. Repeated exposure to water swimming stress with a period of 40 sec, once daily for three days, in combination with lithium chloride did not alter stress-induced antinociception in either phases of the formalin test, when swim stress-induced antinociception was tested on the fourth day. Subchronic treatment with morphine (25 mg/kg), once daily for three days, in the presence or absence of lithium chloride (5 mg/kg) did not alter swim stress-induced antinociception, either, when swim stress-induced antinociception was tested on the fourth day. CONCLUSION It may be concluded that lithium chloride potentiates swim stress-induced antinociception, but the drug has no influence on the response of subchronic administration swim stress or morphine.