Vol. 285, Issue 2, 835-843, May 1998

Regulation of the Na⁺/K⁺-ATPase Pump in Vitro after Long-Term Exposure to Cocaine: Role of Serotonin¹

Scott A. Mackler , Thomas R. Kleyman and Xian-Yuan Cha

Departments of Medicine (S.A.M., T.R.K., X-Y.C.), Psychiatry (S.A.M.) and Physiology (T.R.K.), University of Pennsylvania School of Medicine, Philadelphia VAMC, Philadelphia, Pennsylvania

Long-term exposure to cocaine can cause persistent behavioral changes and alterations in neuronal function. One cocaine-regulated mRNA in the rat brain is the beta-1 subunit of the Na⁺/K⁺-ATPase pump. We examined both Na⁺/K⁺-ATPase function and expression after cocaine treatment of pheochromocytoma cells. One-hour exposure to cocaine did not alter Na⁺/K⁺-ATPase activity, as measured by the ouabain-sensitive component of rubidium uptake. Four days of cocaine resulted in an ~30% decrease in Na⁺/K⁺-ATPase activity. Western blot analyses demonstrated an ~25% decrease in levels of the beta-1 isoform, without changes in pump total alpha subunit levels. Treatment with dopamine type 1 or type 2 receptor agonists for the same period did not affect Na⁺/K⁺-ATPase activity. The serotonin-selective reuptake inhibitor paroxetine caused an ~45% decrease in rubidium uptake after 4 days, whereas pump function was not altered after treatment with either the dopamine-selective reuptake blocker nomifensine or the norepinephrine-selective reuptake blocker desipramine. Chronic treatment with both cocaine and LY 278,584, a serotonin type 3 receptor antagonist, did not replicate the cocaine-associated decrease in pump function. Long-term cocaine exposure regulates expression and function of the Na⁺/K⁺-ATPase pump in neuronal-like cells; this regulation is mediated in part via the serotonin type 3 receptor. Similar Na⁺/K⁺-ATPase pump regulation in vivo may selectively alter neuronal function in the mammalian brain.