Lack of Effect of Lamotrigine on Opioid, Serotonin Type 3 and Cannabinoid Type 1 Receptors in Two Mice Models of Pain

Abstract

Lamotrigine is an anticonvulsant drug with approval for treatment of neuropathic pain. The exact mechanism of action of lamotrigine is still unclear. The current study aimed to screen for the involvement of opioid, serotonin type 3 and cannabinoid type 1 receptors in the antinociceptive effect of lamotrigine using hot-plate and formalin tests. Male albino mice were treated orally with the vehicle or lamotrigine (25, 50 and 100 mg/kg) prior to testing. Further, mice were pretreated with an opioid receptor antagonist, naloxone (0.05 or 0.1 mg/kg, s.c.), the serotonin type 3 receptor antagonist, ondansetron (1 or 2 mg/kg, i.p.) or the cannabinoid type 1 receptor antagonist, rimonabant (0.25 or 0.5 mg/kg, i.p.) before administration of lamotrigine (100 mg/kg). The antinociceptive effect of lamotrigine alone or with specific receptor antagonists was tested in the hot-plate and formalin tests. The results of the current experiment indicated that pretreatment with naloxone, ondansetron or rimonabant did not significantly decrease the antinociceptive effect of lamotrigine in both tests. In conclusion, opioid, serotonin type 3 and cannabinoid type 1 receptors are not involved in the antinociceptive effect of lamotrigine in hot-plate and formalin tests.