Systemic hemodynamic changes raising brain temperature in REM sleep.
The present research studied the mechanisms underlying the increase in brain temperature during REM sleep in the unrestrained rabbit carrying chronically implanted electrodes, thermistors and common carotid artery occluders. During the ultradian wake-sleep cycle at constant ambient temperature (25+/-2 degrees C), we recorded: (i) the ear pinna temperature as an indirect indicator of blood flow affecting heat loss from the systemic heat exchangers of the head, (ii) the temperature of the pons and hypothalamus as indirect indicators of the temperature of vertebral artery blood (systemic cooling only) and carotid artery blood (both systemic and selective cooling), respectively, and (iii) the changes induced in these temperatures by short-lasting bilateral common carotid artery occlusion. The results show that during REM sleep both systemic and selective brain cooling are depressed by a spontaneous decrease in the common carotid artery blood flow and the associated autoregulatory increase in the vertebral artery share of the cerebral blood supply.
Parmeggiani
Pier Luigi
PL
Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Piazza Porta San Donato 2, I-40127, Bologna, Italy. plparm@biocfarm.unibo.it
Azzaroni
Adele
A
Calasso
Marcella
M
D000204:Activity Cycles / Q000502:physiology; D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D002339:Carotid Arteries / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004576:Electromyography; D006439:Hemodynamics / Q000502:physiology*; D007031:Hypothalamus / Q000098:blood supply / Q000502:physiology; D002546:Ischemic Attack, Transient / Q000503:physiopathology; D011149:Pons / Q000098:blood supply / Q000502:physiology; D011817:Rabbits; D012895:Sleep, REM / Q000502:physiology*