Stereotaxic microinjection of HSV-1 selectively decreases striatal dopamine concentrations in mice.

BALB/c mice were stereotaxically injected in the striatum with either the MP or MacIntyre strain of herpes simplex type 1. Three days later, at a time when the animals were free from overt signs of infection, they were killed by cervical dislocation and the striatum was rapidly removed. Concentrations of dopamine, norepinephrine, serotonin and their metabolites were subsequently determined by means of high-performance liquid chromatography with electrochemical detection. With both strains of virus, dopamine levels were reduced and the ratio of homovanillic acid to dopamine was elevated in MP-inoculated mice. Norepinephrine, serotonin and its metabolites were unaffected. Immunoperoxidase staining in separate, identically treated animals indicated that the infection was confined to the striatum and necrosis was minimal at this point in time. These results demonstrate that dopamine metabolism can be affected by herpes simplex in the absence of immunocytochemical evidence of infection of the cell bodies of dopaminergic neurons or cellular death.