AJP - Regulatory, Integrative and Comparative Physiology, Vol 247, Issue 1 135-R145, Copyright © 1984 by American Physiological Society
Forced activity alters sleep cycle periodicity and dorsal raphe discharge rhythm
R. Lydic, R. W. McCarley and J. A. Hobson
Single-cell activity recorded from the brain stem dorsal raphe nucleus
(DRN) of cats showed a regular firing pattern during wakefulness (2-3
spikes/s), decreased activity during slow-wave or synchronized sleep (1
spike/s), and cessation of regular discharge during desynchronized sleep
(0.05 spikes/s). DRN discharge was negatively correlated with the onset and
maintenance of the polycyclic desynchronized sleep rhythm. These findings
were derived from analyses of DRN firing rate sampled during different
behavioral states. The present time-course analyses of DRN discharge
described for the first time the period, amplitude, and phase
characteristics of DRN activity relative to the timing of behavioral states
that comprise the complete sleep cycle. The time course of both DRN
discharge and the occurrence of wakefulness, slow-wave (S) sleep,
transition, and desynchronized (D) sleep were behaviorally manipulated.
Forced locomotor activity imposed by a treadmill task shortened the period
length of the sleep cycle and the duration of the DRN discharge cycle. The
magnitude and direction of these shifts in period length were consistent
across multiple sleep cycles, and there was a high degree of coherence
between the period length of the sleep cycle and the DRN discharge
profiles. The DRN discharge rate also displayed phase dependence within S
and D sleep. These results support the hypothesis that the DRN has a
physiological role in regulating the timing of the ultradian sleep cycle.
