Effects of bilateral vibrissotomy on the expression of focused stereotypy (FS) induced by amphetamine in Sprague Dawley (SD) or Fischer 344 (F344) rats

Abstract

Above doses of about 2.5 mg/kg in SD rats, amphetamine produces FS, a syndrome characterized by a complete lack of locomotion accompanied by rapid, rhythmic head movements. During these movements, the rat’s vibrissae are stimulated by accelerations of the head and by contact with the floor and walls of the cage. Given that previous reports have linked removal of vibrissae with changes in brain dopamine systems and given amphetamine’s dopamine releasing effects in vivo, we hypothesized that bilateral removal of the vibrissae would alter the FS response to amphetamine. Of additional interest was the question of rat strain differences in response to amphetamine. Accordingly, in a between-groups dosing design male SD and male F344 rats were treated with 0, 1.25, 2.5 and 5.0 mg/kg d-amphetamine sulfate every 4th day for a total of 7 injections, and on the 7th day, amphetamine treatment was accompanied by bilateral vibrissotomy. Behavior was recorded continuously in 4-hr sessions with a force-plate actometer, a new type of technology that permits quantitation of FS without human observers. Vibrissotomy did not alter the basic style of FS for either rat strain where style was assessed by the power spectra of the vertical force component of the head movements. Area-under-the-curve analyses of FS scores showed vibrissotomy increased the intensity of the head movements in the F344 rats but not in the SD rats. Indexes of spatial confinement were not significantly affected. These data suggest that the rhythmic, rapid head movements of FS are probably not sustained by, nor appreciably modulated by sensory feedback from the vibrissae. Supported by MH43429 and HD002528.