Pontine neuronal response to local cholinergic infusion: relation to REM sleep.

In behaving cats, a cholinergic agonist, carbachol, or Ringer's solution were infused into the pontine reticular formation (PRF). Extracellular microelectrode recordings were obtained from single neurons located 1-4 mm from the infusion site. Sleep polygraphic variables were also recorded. Carbachol microinfusions into the PRF area between the locus coeruleus and the genu of the seventh nerve readily triggered some or all of the tonic and phasic components of REM sleep. The resulting REM-like states had a mean duration of 30 min. In 56 reticular units studied during carbachol infusions, compared to Ringer's, we observed the following significant responses: 26.6% (16 cells) increased discharge rate, 55.4% (31 cells) decreased discharge rate, 12.5% (7 cells) showed no change, while 3.5% (2 cells) showed a biphasic response. Both incremental and decremental neuronal responses evoked by carbachol preceded or coincided with the onset of REM-like sleep periods, and persisted throughout these periods. The subpopulation of cholinoceptive PRF neurons accelerated during both spontaneous and carbachol-induced REM sleep is most likely to account for REM sleep triggering by carbachol. The PRF neurons found to be decelerated by carbachol displayed under control conditions, the accelerated discharge pattern during REM sleep which is typical of PRF neurons. Since either discharge acceleration or deceleration may occur during REM-like states the discharge pattern of this subpopulation of PRF neurons may not be critical for REM sleep generation.