REM sleep deprivation effect on apomorphine-induced gnawing is reversed by dexamethasone.

Glucocorticoid feedback was manipulated in rats deprived of REM for six days or left undisturbed in their home cages. One half of each group received concurrent dexamethasone (400 micrograms/kg), while the other half received corn oil. On test day, rats were observed for 5 min, injected with apomorphine (0.8 mg/kg, i.p.), and again observed. Dexamethasone revealed REM-deprivation-enhanced stereotypical gnawing, but had no effect on REM-deprivation-reduced rearing, suggesting the involvement of catecholamine depletion by non-specific stress-related factors in the former REM deprivation effect.