Characteristics of oral movements in rats during and after chronic haloperidol and fluphenazine administration

Abstract

Rats were chronically administered either haloperidol (HAL) or fluphenazine (FLU) via depot injections for 8 months, given these same drugs in their drinking water for the next 2 months, and then withdrawn from the drugs. Throughout the experiment the animals were tested repeatedly in an enclosed tube using a computerized device which measured computer-scored movelets (CSMs) and, in the latter half of the experiment, were also scored by a human observer in the tube, as well as in an open cage, for observed oral movements (OMs). In the tube, the animals in both neuroleptic-treated groups showed initial decreases in the number of CSMs and made sluggish CSMs; these effects were generally larger in the FLU animals. After 6 months of chronic neuroleptics, the HAL-treated animals showed increased oral movements, both as reported by the human observer and in CSMs of all amplitudes, and this effect increased upon drug withdrawal. FLU-treated animals showed a more persistent depression of both OMs and CSMs of large amplitudes. However, the behavior most characteristic of both neuroleptic-treated groups was the gradual development of increases in CSMs of the smallest amplitudes measurable. A different pattern was observed in the open cage test, where both neuroleptic groups showed significant increases in vacuous OMs during drug administration which rapidly became attenuated upon drug withdrawal. These results indicate a complex syndrome of oral activity in the drugged animals which changed over time. The measure of oral activity which most clearly showed the time-course for late-onset changes in oral activity was CSMs of the smallest amplitudes.