Selective increase in brain dopamine metabolism during REM sleep rebound in the rat

Rats implanted with electrodes for EEG and EMG recording were placed on small or large platforms for either 24 or 96 hr and the effects on the subsequent REM sleep rebound were observed. Only the 96 hr protocol produced a selective REM sleep rebound in rats placed on small platforms. Brain MOPEG-SO₄, a final metabolite of norepinephrine, was determined fluorometrically and dopamine metabolites HVA and DOPAC, as well as the serotonin metabolite 5-HIAA, were measured by using an HPLC method with electrochemical detection. The results show that selective increases in brain HVA and DOPAC were obtained only during the REM sleep rebound in rats from small platforms. Non-specific increases were observed in MOPEG-SO₄ and 5-HIAA during the recovery period in rats from both small and large platforms which could be related to the effects of immobilization stress.