Mild insomnia induced by environmental perturbations in the rat: a study of this new model and of its possible applications in pharmacological research.

This paper describes an experimental model for testing new products in a situation where sleep is impaired by a nonpharmacological procedure. This model consists in studying the effect of hypnogenic substances on sleep perturbations which take place when chronically implanted rats are moved to a novel individual cage, connected for the first time to their recording cable and dosed intragastrically with test products, vehicle or placebo. Continuous polygraphic recordings were taken throughout the daily treatment period (15 days) and scored for the presence of slow wave sleep (SWS), and rapid eye movement sleep (REM). The hourly vigilance stages were also computed to determine the parameters of their nycthemeral rhythms. In vehicle-treated rats, a decrease in SWS and REM values and a delay of SWS and REM phases of nycthemeral rhythms occurred on the first day as compared with the end of the recording period. Phenobarbital (5 mg/kg p.o.), mecloqualone (5 mg/kg p.o.) and a new benzodiazepine CM 7302 (7 mg/kg p.o.) led to an immediate or fast recovery, whereas no improvement was observed with placebo and with clorazepate dipotassium (9 mg/kg p.o.). This model can be considered as an attractive model for studying mild insomnia because it allows "true" hypnogenic drugs to be selected in a minimum amount of time.