Effects of imipramine, chlorimipramine, and fluoxetine on cataplexy in dogs.

Four narcoleptic dogs with cataplexy were given trials with the serotonin uptake blockers imipramine and chlorimipramine (known to be effective in treating cataplexy in humans). An even more selective serotonin uptake blocker, fluoxetine, was also tested. Injections of placebo, test compound, and placebo were given respectively on 3 successive days. Anticataplectic effects were measured approximately 30 min, 3 hr, and 6 hr postinjection by recording elapsed time and number of cataplectic episodes during the dogs' attempts to eat ten pieces of a desired food presented in a standard fashion. Imipramine (1 mg/kg) and fluoxetine (1.5 and 3.0 mg/kg)significantly improved performance, while chlorimipramine (0.5-5 mg/kg) had no clear effect. Data were not totally consistent with the notion that serotonin uptake blockers improve cataplexy in dogs, since chlorimipramine was not effective in these animals.