Neuroleptic-induced oral movements in rats: methodological issues.

In three separate experiments groups of rats were chronically administered neuroleptics in a variety of ways (chronic injections, subcutaneous implants, and decanoate injections) and examined for oral movements (OMs) in two different tests: in an open cage using a human observer, or in a plexiglas tube enclosure, where OMs were monitored both by a human observer and computerized video analysis system. These two testing methods showed different effects of neuroleptic administration. In the open cage, OMs tended to be enhanced during chronic neuroleptic exposure and to rapidly subside upon drug withdrawal. The enhanced OMs were especially present just after drug injections, when activity levels were low. In the observation tube environment, however, OMs tended to be low soon after drug treatments, and elevated upon withdrawal. Thus, the type of behavioral test used determines how neuroleptic-induced increases in oral activity should be interpreted.