Modulation of the levels of ouabain-like compound by central catecholamine neurons in rats

Catecholamine regulates the Na+,K(+)-ATPase activity in the central nervous system and the Na+,K(+)-ATPase has been shown to have endogenous ligands (ouabain-like compound; OLC). To examine the relationship between OLC and central adrenergic neurons, we evaluated the effects of central sympathectomies with intracerebroventricular (i.c.v.) injection of 6-hydroxydopamine (6-OHDA; 250 micrograms) on brain and plasma OLC levels and brain catecholamine levels. In centrally sympathectomized rats, hypothalamic OLC content and plasma OLC level were significantly decreased by 90% (P < 0.01) and 70% (P < 0.01), respectively, in accordance with reduced brain norepinephrine content compared with control rats pretreated by i.c.v. injection of vehicle (ascorbic acid). On the other hand, peripheral sympathectomy with a similar manner did not affect plasma OLC level at all. These findings suggest that central adrenergic neurons may be involved in the synthesis and/or release of circulating OLC.