Heat vasodilatation of the rat tail.

The vasomotor response of the tail of the albino rat to total-body heating and cooling was studied by skin-temperature recording and plethysmography with the tail at 25 degrees C air temperature. Tail vasodilation started at core temperatures lightly above 37 degrees C and increased to a core temperature up to about 39 degrees C. During cooling of warm rats, tail vasoconstriction started at significantly higher levels of core temperature than the values at which vasodilation appeared when the rat was warmed.