Neuronal activity in the caudolateral peribrachial pons: relationship to PGO waves and rapid eye movements.

1. The present study was performed to examine the hypothesis that the caudolateral peribrachial area (C-PBL) may be directly involved in shifting the brain from the nonpontogeniculooccipital (non-PGO)-related states of waking (W) and slow-wave sleep (S) to the PGO-related states of slow-wave sleep with PGO waves (SP) and rapid eye movement (REM) sleep. 2. To test this hypothesis at the cellular level, we have recorded a sample of 226 spontaneously discharging units of the C-PBL during natural sleep-waking cycles in unanesthetized head-restrained cats and have correlated the action-potential data with the PGO waves. 3. Of these 226 cells, 67.26% (n = 152) were called PGO state-on units because they increased or began firing 15-5 s before the first PGO wave of SP and maintained their high firing rate throughout SP (31.30 +/- 6.0 Hz, mean +/- SD) and REM sleep (39.46 +/- 6.70 Hz); their firing rates in W (0.45 +/- 0.85) and S (0.70 +/- 1.26) were much lower. Among these PGO state-on neurons, 28.94% (n = 44) discharged high-frequency (> 500 Hz) spike bursts on the background of tonically increased firing rates during the PGO-related states. Contrastingly, 14.16% (n = 32) of the cells (called PGO state-off units) fired tonically during W (11.54 +/- 4.15) and S (9.43 +/- 3.87) but stopped or decreased firing 25-15 s before the first PGO wave of SP; their activity remained suppressed throughout SP (0.19 +/- 0.44) and REM sleep (0.03 +/- 0.17). The remaining 18.58% (n = 42) cells fired (9-10 Hz) tonically but were unrelated to the wake-sleeping cycle. 4. During SP and REM sleep, primary PGO waves were found to appear with equal frequency in each lateral geniculate body (LGB). During REM sleep these primary waves were ipsilateral to the direction of phasic rapid eye movements as previously reported by Nelson et al. (1983). 5. During SP and REM sleep PGO state-on burst cells fired high-frequency bursts on a background of tonic activity in association with each ipsilateral primary LGB PGO wave. The first spike of a burst preceded the beginning of the negative component of the ipsilateral LGB PGO waves by 25 +/- 7.5 ms. On the basis of their sustained firing and the latency of their PGO-related bursting, we call these neurons long-lead PGO-on burst-tonic cells.(ABSTRACT TRUNCATED AT 400 WORDS)