Compromised peripheral immunity of mice injected intrastriatally with six-hydroxydopamine.

Intracisternal or intracerebroventricular administration of six-hydroxydopamine (6-OHDA), which results in decreased norepinephrine (NE) and dopamine (DA) levels throughout the brain, causes impaired peripheral immunity. However, in vivo immunocompetence following selective striatal depletion of DA by 6-OHDA has not been investigated. Thus, we sought to determine whether striatal DA depletion compromises host resistance to Listeria monocytogenes (LM) and impairs the immune response to keyhole limpet hemocyanin (KLH). Mice treated with 6-OHDA (90% decrease in striatal DA) had (i) increased LM colonization in liver and spleen, (ii) lower primary IgM and IgG(1) antibody titers, as well as secondary IgM titers, and (iii) compromised DTH response compared to controls. Co-administration of a DA uptake inhibitor partially (40%) spared striatal DA depletion and completely prevented the increase in LM burden, but was ineffective in preventing any of the 6-OHDA-induced suppressions of the immune responses to KLH. Thus, striatal DA is suggested to play a response-specific role in peripheral immunological functions.