LOW-THRESHOLD NEURONAL ACTIVITY OF SPINAL DORSAL HORN NEURONS INCREASES
DURING REM SLEEP IN CATS: A COMPARISON WITH EFFECTS OF ANESTHESIA.
Kishikawa, K., H. Uchida, Y. Yamamori, J.G. Collins.
Department of Anesthesiology, Yale University School of Medicine, New
Haven, CT 06510, USA.
APStracts 2:0092N, 1995.
SUMMARY AND CONCLUSIONS
1.Cats were prepared for chronic recordings from the lumbar enlargement of the
spinal dorsal horn. At the beginning of each recording session, a tungsten
microelectrode was advanced through the dura in a physiologically intact,
awake, drug-free animal, until amplitude discrimination provided a single
neuron with a receptive field on the hindquarters. 2.Extracellular recordings
of activity of each neuron were made during receptive field stimulation with
tactile and thermal non-noxious and noxious stimuli. 3.Baseline responses
obtained in the awake state were compared with responses of the same neurons
during slow wave or REM sleep. In a subpopulation of neurons, the effects of
anesthesia (propofol 7.5 mg/kg i.v.) were observed after the completion of
sleep studies. 4.The low-threshold receptive fields of the 7 neurons studied
during REM sleep were all increased in size when compared with the baseline
value. The average increase was 52.6% (range 26.2-96.7%). 5.The low-threshold
receptive fields of the 7 neurons studied during REM sleep were reduced by
propofol anesthesia by an average of 49.1% (range 29-74%). 6.Neuronal response
to receptive field brushing was observed in 15 neurons during REM sleep. The
effect of propofol on receptive field brushing was observed in 8 of those
neurons. In only one of those 8 neurons were the effects of REM sleep and
anesthesia in the same direction. 7.Changes in neuronal responses were less
consistent during slow wave sleep but still differed from changes induced by
propofol. 8.These results demonstrate important differences between effects of
natural sleep and anesthetic induced loss of consciousness on sensory
processing in the spinal dorsal horn. They also demonstrate significant
disinhibition/excitation during REM sleep resulting in enhanced response of
spinal dorsal horn neurons to low-intensity receptive field stimulation.
Received 29 April 1994; accepted in final form 29 March 1995.
APS Manuscript Number J225-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.