Really does temperature reduction and norepinephrine have similar effects on the energy metabolism in rat brown adipose tissue?

Heat generation by brown adipose tissue (BAT) in response to temperature reduction seems to be entirely related to sympathetic nervous stimulation.

To analyse if temperature reduction and norepinephrine may differently affect the expression of proteins related to energy metabolism in BAT.

Isolated rats BAT was incubated with/without norepinephrine (10^-6 mol/L, 24 h at 32 °C and 37 °C).

In BAT, 32 °C increased the protein expression levels of carnitine palmitoyltransferase-I and -II, mitochondrial uncoupling protein-1 (UCP-1) and the expression and activity of lactate dehydrogenase. Mitochondrial F₁-ATP synthase α-chain expression was decreased at 32 °C compared to 37 °C. Norepinephrine and at 32 °C exposure, UCP-1 expression was increased but cytochrome-c oxidase and F₁-ATP synthase α-chain expression was reduced with respect to 37 °C.

Sympathetic stimulation seems not to be the only factor associated with heat generation.

Temperature reduction by itself exerts some different effects on the expression of proteins related to the energy metabolism than norepinephrine.