Participation of alpha-adrenoreceptors in brown adipose tissue thermogenesis in vivo.

Norepinephrine-induced BAT thermogenesis in anaesthetized cold-acclimated rats was markedly inhibited by alpha1-adrenoreceptor antagonists (eg prazosin). The inhibition was relieved by infusion of alpha1-agonists (eg phenylephrine). The beta-agonist, isoproterenol, was a relatively poor activator of BAT thermogenesis in vivo, but became a potent activator when combined with doses of phenylephrine that when given alone did not stimulate BAT thermogenesis. Phenylephrine also potentiated the thermogenic response of BAT to suboptimal doses of norepinephrine. The effects of prazosin and phenylephrine on BAT thermogenesis were shown to occur at the level of the BAT itself.