COMPARATIVE EFFECTS OF MODAFINIL AND AMPHETAMINE ON DAYTIME SLEEPINESS AND CATAPLEXY OF NARCOLEPTIC DOGS

The effects of modafinil and amphetamine on daytime sleep (polysomnogr aphic recordings) and cataplexy (the food-elicited cataplexy test) wer e compared using the narcoleptic canine model. Results indicate that b oth modafinil (5 and 10 mg/kg body weight i.v.) and amphetamine (100 a nd 200 mu g/kg i.v.) increase wakefulness and reduce slow-wave sleep i n control and narcoleptic dogs. In contrast, the results of cataplexy testing demonstrate that amphetamine (2.5-160 mu g/kg i.v.), but not m odafinil (0.125-8.0 mg/kg i.v.) significantly suppresses canine catapl exy. These results suggest that the pharmacological property of modafi nil is distinct from amphetamine. Results of polysomnographic recordin gs also demonstrate that narcoleptic dogs slept significantly more dur ing the daytime than control dogs and required very high doses (10 mg/ kg i.v. modafinil; 200 mu g/kg i.v. amphetamine) of stimulants to redu ce their level of sleepiness to that of control dogs. This finding is consistent with the data collected in human narcolepsy and validates t he use of this canine model for the screening of stimulant compounds.