Autonomic basis for the rise in brain temperature during paradoxical sleep.

The rise in brain temperature in the rabbit during paradoxical sleep originates in a temperature rise of the cerebral arterial blood. Heat loss from the ear is a major factor in the regulation of arterial blood temperature in the rabbit, and the primary thermal event in paradoxical sleep is a vasoconstriction of the skin of the ear which results in a rise in arterial blood and brain temperatures. These thermal correlates of paradoxical sleep are not present in a cold environment when the ear skin is already maximally vasoconstricted. The persistence of peripheral vasoconstriction during paradoxical sleep in a hot environment suggests a disturbance in autonomic thermoregulatory control.