ADRENERGIC REGULATION OF NEONATAL BROWN FAT ADENYLYL CYCLASE AND GS-ALPHA ACTIVITY

Norepinephrine (NE)-stimulated adenylyl cyclase (AC) activity increases during the perinatal period in rat brown adipose tissue (BAT), and this increase is associated with changes in the activities of both the catalytic subunit (C) and G(s-alpha), the GTP-binding protein that mediates activation of C. The present study examined the role of the sympathetic nervous system in the postnatal sensitization of AC. The sympathetic innervation of BAT increased 7- to 13- fold after birth, and this increase was temporally correlated with the postnatal enhancement of AC responsiveness. 6-hydroxydopamine (6-HDA) treatment of neonates reduced tyrosine hydroxylase levels by > 90%. This treatment greatly reduced the perinatal increase in NE- and NaF-stimulated AC and completely abolished the increase in forskolin-Mn2+-stimulated activity. However, sympathectomy did not alter the postnatal increase in G(s-alpha)-specific activity and did not prevent the postnatal reduction in G(s-alpha) levels. These results demonstrate that the sympathetic innervation of BAT develops fully after birth and is essential for the postnatal increase in the activity of C but not of G(s-alpha).