What are the parts of the rat's tail?
The rat's tail is an extension of the vertebral column that projects out the back side of the animal. The tail is a long cylinder consisting of three concentric layers. The innermost core of the tail is bone (vertebre). The bone is surrounded by a layer of tendons, and the tendons are surrounded by a layer of skin. Blood vessels run the length of the tail between the tendons.

Cross-section of a rat's tail. Drawing adapted from Vanhoutte et al. 2002

What are the functions of the rat's tail?
Thermoregulation
The rat's tail has a thermoregulatory function: it serves as a heat-loss organ. The tail is well suited for this purpose, because it has no fur, has a large surface to volume ratio, and is perfused with many blood vessels, especially at the tail tip and midlength (Yulong et al. 1995). The rat's tail comprises only 5% of the rat's surface area, but it can dissipate about 17% of the rat's body heat (Monson and Oyama 1984).
Rats control their body temperature through their tails by dilating or constricting their tail blood vessels. When the rat's body temperature rises by a few degrees, the tail vessels (especially the veins) swell -- called vasodilation -- permitting lots of warm blood to flow through the tail (Vanhoutte et al. 2002). The warm blood loses heat through the surface of the tail and returns to the body at a lower temperature, thus cooling the rat. The warmer the rat, the more blood flows through the tail, and the more heat is lost (Thompson and Stevenson 1965, Little and Stoner 1968, Rand et al. 1965, Raman et al. 1987).
When the rat's body temperature drops, the tail vessels shrink in diameter -- called vasoconstriction -- thus restricting blood flow to the tail (Owens et al. 2002). Less blood flows into the tail for cooling, and body heat is conserved.
n un modelo de disfunción termorreguladora en ratas ovariectomizadas, DVS-233 "mostró una rápida aparición de la acción en la recuperación de la reducción normal de la temperatura de la piel de la cola" en la fase activa (ciclo oscuro) de un ciclo diario de la rata.

In ovariectomized rats with thermoregulatory dysfunction, DVS-233 caused a rapid recovery of the normal temperature reduction in their tail skin.