Brain monoamine metabolism and rotational behaviour induced by experimental herpes simplex virus encephalitis

The motor behaviour and brain concentrations of dopamine, noradrenaline, serotonin and their metabolites have been examined in rabbits with experimental herpes simplex virus (HSV) brain infection achieved by unilateral corneal inoculation. The animals showed altered motor behaviour, consisting of a posture tilting to the side of inoculation and circling in the same direction, that began on day 4-5 post inoculation, and was most vigorous on day 7 post inoculation. Compared with controls, the concentration of 5-hydroxyindoleacetic acid was increased in the caudate nucleus on both sides and that of serotonin was decreased in the nucleus accumbens on the side of inoculation. The circling of the animals correlated positively with the ratio of homovanillic acid concentrations between the left and right caudate nucleus, although the actual concentrations did not differ from the controls. The posture asymmetry correlated with the ratio of the left and right nucleus accumbens homovanillic acid concentrations. The results demonstrate that experimental HSV infection in the brain alters motor behaviour, in association with changes in brain dopamine and serotonin metabolism in the major ascending monoamine systems.