1. Ephedrine and caffeine (EC) combination has been widely used in human obesity treatment, and is still present in many herbal preparations sold widespread in many countries for weight loss. It is well known that this drug increases the metabolic rate in both animals and humans. Ephedrine is an agonist of both α and β-adrenoceptors; moreover, it induces norepinephrine release from sympathetic neurons, and thus is a sympatho-mimetic drug with a mixed profile. Caffeine increases both norepinephrine and dopamine release and stimulates the neuronal activity in several brain regions. In addition, caffeine antagonizes the inhibitory effects of adenosine on sympathetic nervous system (SNS). This modulation of SNS activity may be a possible explanation for the thermic effect of EC. In fact, epinephrine activates the uncoupling protein 1 (UCP1), a member of mitochondrial carriers localized on the inner mitochondrial membrane in brown adipocytes. The physiological role of UCP1 is to uncouple oxidative phosphorylation, therefore most of the energy is dissipated as heat rather than being converted to ATP. UCP1 is unique to brown adipocyte mitochondria, although brown-like multilocular adipocytes expressing UCP1 interspersed within human WAT have been observed. Actually, UCP1 mRNA has been detected in all adipose tissues in adult humans, and it has been estimated that 1 in 100-200 adipocytes in human intraperitoneal adipose tissue expresses UCP1. It has been shown that the cold-induced occurrence of brown-like adipocytes and UCP1 requires the presence of the β3-adrenoceptor in previously white adipose tissue and the presence of the β3-adrenoceptor is required for full stimulation of energy expenditure and oxygen consumption in white adipose tissue.