6-HYDROXYDOPAMINE INDUCES THYMOCYTE APOPTOSIS IN MICE

6-Hydroxydopamine (6-OHDA) induces degeneration of noradrenergic nerve s and has been shown to alter the immune responses. In this study, int raperitoneal administration of 6-OHDA induces mouse thymus atrophy. Th e lowest levels of thymus weight and cell number were reached at days 3 and 5 in mice receiving 6-OHDA treatment; they gradually recovered t hereafter. On flow cytometry analysis, the most substantial reductions were recorded for CD4(+)CD8(+) thymocytes, although the numbers of ot her subpopulations, i.e. CD4(+)CD8(-), CD4(-)CD8(+) and CD4(-)CD8(-) c ells were also reduced. DNA fragmentation, a characteristic of apoptos is, was detected in the thymocytes following 6-OHDA injection. Pretrea tment with desipramine greatly blocked the reduction in thymus size an d thymocyte number, the changes in thymocyte subpopulations, the perce ntage of subdiploid (apoptotic) cells and the appearance of DNA fragme nted bands. Furthermore, 6-OHDA-induced thymocyte apoptosis could also be detected in vitro, and was blocked by desipramine treatment. These results indicate that 6-OHDA induces mouse thymocytes to undergo apop tosis both in vivo and in vitro, and this effect is inhibited by catec holamine uptake blocker.