CHRONIC LOW-AMPLITUDE ELECTRICAL-STIMULATION OF THE LATERODORSAL TEGMENTAL NUCLEUS OF FREELY MOVING CATS INCREASES REM-SLEEP

While cholinergic stimulation of the PRF evokes a REM-like state, elec trical stimulation of LDT/PPT neurons has not been used to test the hy pothesis of mesopontine cholinergic control of REM sleep. Adult cats w ere implanted for electrographic recording and with bipolar unilateral stimulating electrodes, either in the LDT or within the PRF (stimulat ion control). Baseline recordings of the normal sleep-wake cycle were carried out for 5 h. On the next day, continuous stimulation of the LD T or mPRF was carried out during the same time period (0.5 ms pulses, 1 mu A, 8 Hz) and with post-stimulation recording for 3 h. A second ba seline recording day followed with same protocol as the first baseline day. This 3-day sequence, separated by 3 days, was repeated three tim es in each of the three LDT and the three medial PRF cats. Five hours of chronic low-amplitude stimulation of the LDT induced a highly signi ficant increase in total REM and in the duration of REM sleep bouts. S timulation of the mPRF did not affect any of the behavioral states. Th is study, the first to our knowledge to use low-amplitude stimulation of LDT in freely moving cats, indicates the importance of mesopontine cholinergic neurons in REM sleep.