AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 111-H119, Copyright © 1989 by American Physiological Society
Heart rate and blood pressure changes during sleep-waking cycles and cataplexy in narcoleptic dogs
J. M. Siegel, K. S. Tomaszewski, H. Fahringer, G. Cave, T. Kilduff and W. C. Dement
Neurobiology Research, Sepulveda Veterans Administration Medical Center, California 91343.
Cataplexy is the abrupt loss of muscle tone experienced by narcoleptics. It
is usually precipitated by strong emotions or athletic activity. It has
been hypothesized that cardiovascular variables have a role in the
triggering of cataplexy. In the present study, we have utilized the
narcoleptic canine model to directly investigate changes in heart rate and
blood pressure in relation to cataplectic episodes. We found that heart
rate increased 18% on average in the 20 s preceding cataplexy onset and
then fell during cataplexy. Thus, from a cardiovascular standpoint,
cataplexy can be subdivided into two very different periods, the cataplexy
onset period with very high and declining heart rate, and the period
greater than or equal to 10 s after onset, with greatly reduced heart rate.
Heart rate at cataplexy onset was significantly higher than heart rate in
rapid-eye-movement (REM) sleep, non-REM sleep, and quiet waking. Blood
pressure did not markedly change before the onset of spontaneous
cataplexies but decreased significantly during cataplexy. Although blood
pressure increases did not precede spontaneous cataplexies, sudden
increases in blood pressure, induced pharmacologically or by obstruction of
the descending aorta, triggered cataplexy in the most severely affected
subjects. A hypothesized role for cataplexy as a homeostatic reflex,
triggered by interactions between blood flow, central chemoreceptors, and
atonia control mechanisms in the medial medulla, is discussed.
