Study of neuropathologic changes in the striatum following 4, 8 and 12 months of treatment with fluphenazine in rats.

Persistent tardive dyskinesia is a serious side effect of long-term treatment with neuroleptics. Although striatal pathologic changes are believed to underlie this potentially irreversible iatrogenic syndrome, the nature of the neuroleptic-induced neuropathology is unclear. In the present study, we treated rats with either vehicle or fluphenazine decanoate (5 mg/kg, IM) every 2 weeks for 4, 8 or 12 months. Four to nine weeks after the last injection, the animals were sacrificed and the density of cells in the central part of the striatum was measured with a computerized image-analysis system. The control and experimental animals did not differ in body weight with 4 and 8 months of treatment, but the rats treated with fluphenazine for 12 months had significantly lower body weights than comparable controls. Four months of neuroleptic use produced no significant neuropathologic changes. The animals treated with fluphenazine for 8 months had a significantly lower density of the large neurons. In the 12-month-treated group, there was no significant difference between the control and experimental animals, probably because of a 'floor effect': the density of the large neurons was significantly lower in the 12-month-treated compared to the 8-month-treated control rats.