Alpha 2-adrenergic receptors in brown adipose tissue of infant rats--II. Studies on function and regulation

1. Clonidine inhibited the forskolin- and MIX-induced rate of lipolysis in brown fat adipocytes isolated from interscapular brown fat of 7-day-old rats. Its effect could be prevented by the alpha 2-antagonist yohimbine. 2. Pertussis toxin prevented the above effect of clonidine, thus indicating that alpha 2-adrenoceptors are linked with adenylate cyclase via the Ni regulatory subunit. 3. Chemical sympathectomy of 5-day-old rats by 6-hydroxydopamine increased the number of low-affinity alpha 2 sites in brown fat. 4. Chronic administration of yohimbine to 2-3-week-old rats also increased the density of alpha 2-adrenoceptors in brown fat. 5. It is suggested that brown fat of infant rats possesses functional alpha 2-adrenoceptors.