REM sleep deprivation (REMSD) antagonizes naloxone-precipitated withdrawal in acute morphine-dependent rats

In rats allowed undisturbed sleep (control and stress) the administration of naloxone (10 mg/kg, s.c.) to morphine (7.5 mg/kg, s.c. 90 min prior) pretreated animals precipitated a jumping behaviour. REM sleep deprivation (REMSD 96 h, prior) significantly decreased the frequency of the naloxone-precipitated jumping behaviour compared with control and stressed animals. In second animal model for morphine withdrawal, naloxone (10 mg/kg, s.c.) provoked myoclonic twitch activity (MTA) in rats previously exposed to morphine (7.5 mg/kg, s.c., 90 min prior). The intensity of naloxone-induced MTA in REM sleep deprived rats was significantly lower compared to stressed animals, but it is not different from the control group. It is suggested that REMSD interferes with a neural mechanism involved in the development of acute dependence. Results are discussed in light of a possible functional insufficiency of a mu-opioid system during REMSD.