Activity of ventromedial hypothalamic neurons suppressing heart rate is associated with paradoxical sleep in the rat.
Cardiovascular change is one of the common features of paradoxical sleep. Our study offers evidence that one of the central areas regulating the circulation during sleep is the ventromedial nucleus of the hypothalamus (VMH). We found a group of neurons in this hypothalamic nucleus of rats whose electrical activity was exclusively increased during paradoxical sleep, and was associated with a reduction in heart rate. The onset of this neural activity usually followed that of paradoxical sleep. The incidence and duration of paradoxical sleep was increased by means of microinjection of carbachol, a cholinergic agonist, into the pontine reticular formation, and the neural activity of the VMH still appeared in synchrony with carbachol-induced paradoxical sleep. These results suggest that the cholinergic paradoxical sleep-inducing mechanism in the pons facilitate the excitability of these neurons. We have previously shown that these VMH neurons suppress blood pressure and heart rate via inhibition of the vasomotor neurons in the medulla oblongata. Taken together, our findings suggest that a group of neurons in the VMH suppresses the circulatory system during paradoxical sleep.
Hirasawa
M
M
Department of Veterinary Physiology, Veterinary Medical Science, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan.
Nishihara
M
M
Takahashi
M
M
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002320:Cardiovascular Physiological Phenomena; D004569:Electroencephalography; D004585:Electrooculography; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D010277:Parasympathomimetics / Q000494:pharmacology; D017286:Polysomnography; D051381:Rats; D017207:Rats, Sprague-Dawley; D012154:Reticular Formation / Q000187:drug effects / Q000502:physiology; D012895:Sleep, REM / Q000187:drug effects / Q000502:physiology*; D014697:Ventromedial Hypothalamic Nucleus / Q000502:physiology*
D010277:Parasympathomimetics; D002217:Carbachol