Discharge patterns of the nucleus parabrachialis lateralis neurons of the cat during sleep and waking.

Discharge patterns of the nucleus parabrachialis lateralis (PbL) neurons located in the dorsolateral pontine tegmentum were investigated in 7 unrestrained, freely behaving cats with a multiwire electrode bundle method. Among 84 PbL units recorded so far, 31% of the units exhibited a marked reduction or complete cessation of firing during paradoxical sleep (PS) (PS-off cells), while 55% of the units exhibited an increase of firing during PS (PS-on cells) as compared with quiet wakefulness (QW) and slow wave sleep (SWS). The remaining 14% of the PbL units exhibited no remarkable change of firing rate and pattern during the sleep-walking cycle. The PbL PS-off cells were further characterized by a slow and regular firing pattern during QW and SWS, and they were similar in several respects to the PS-off cells reported in the nucleus raphe dorsalis and locus coeruleus complex. Six of the PbL PS-on cells were tightly phase-locked with PGO waves, and the spikes preceded by 5-25 msec the onset of the PGO waves recorded in the lateral geniculate nucleus. Seven other PbL PS-on cells were related to the locomotor activity observed in active wakefulness. In light of the present results, the functional significance of the PbL units has been discussed.