Abstract

This study presents the actions of risperidone (Risp) and haloperidol (Hal) on the behavioral effects elicited by ketamine (Ket) on open-field (OF), rota rod (RR) and tail suspension (TS) tests in mice. Male Swiss albino mice (25–30g) were used. Antipsychotics were administered alone (Risp: 0.1 or 0.2 mg/kg, ip; Hal: 0.1 and 0.2 mg/kg, ip) or thirty minutes before Ket (10 mg/Kg, ip). Ket increased (Ket: 63.3 ± 4.2) the locomotor activity compared to control, while neuroleptics decreased it (25.5 ± 4.2). Pretreatment with neuroleptics, in both doses, blocked hyperlocomotion caused by Ket. In RR, Ket decreased (Ket: 15 ± 4.1) the permanence time of the animals compared to control (Control: 59 ± 0.6), but this effect was not observed when neuroleptics were administered alone. Pretreatment with neuroleptics reverted the effect of Ket only in the RR. While Ket (17.3 ± 5.6) decreased the time of immobility in the tail suspension test compared to the control (80.2 ± 10.2), the pretreatment with neuroleptics reverted this mobility. The action of neuroleptics in this model made possible the blockade of the effects caused by acute administration of Ket. Thus, the mechanism of action of ketamine may involve the dopaminergic system.