ATRIAL-NATRIURETIC-FACTOR MODIFIES NORADRENALINE RELEASE IN A SODIUM-FREE MEDIUM

1 The effects of atrial natriuretic factor (ANF) on H-3-noradrenaline (H-3-NA) release evoked by a sodium-free medium (SFM) were studied. Th e experiments were carried out in rat hypothalamic slices incubated in vitro. 2 ANF (1, 10 and 100 nM) decreased NA release evoked by the om ission of sodium in a concentration-dependent way. When calcium was om itted from a SFM, NA output was partially diminished. However, if ANF was added to the SFM/calcium free medium NA secretion showed no modifi cations. 3 Present results suggest that, in rat hypothalamus, NA relea se evoked by Na+ omission is divided into two fractions: one independe nt of and the other dependent on extracellular calcium. In addition, A NF modifies NA release evoked by SFM dependent on extracellular calciu m.