CONICET | Buscador de Institutos y Recursos Humanos

SEXUALLY DIMORPHIC ANXIETY-LIKE BEHAVIOR DURING MORPHINE WITHDRAWAL SYNDROME 1,2Induni, A S, 1Varani, A, 1Machado, L, 1Calvo, M, and 1,2Balerio G. 1ININFA (CONICET), 2Cát. de Farmacología, FFyB (UBA). Junín 956 5º piso (1113), Buenos Aires. E-mail: gbalerio@ffyb.uba.ar We have previously demonstrated sex differences during morphine (MOR) withdrawal. We have also shown that the GABAB receptor agonist baclofen (BAC) was able to prevent the MOR withdrawal in male as well as female mice. The aim of the present study was to evaluate the anxiety-like behavior in mice of either sex during naloxone (NAL)-precipitated withdrawal and its prevention with BAC in the elevated plus maze (EPM). Swiss-Webster prepubertal mice were rendered dependent by i.p. injection of MOR (2 mg/kg), twice daily for 9 days. On the 10th day, dependent mice were divided into two groups: withdrawal group received NAL (6 mg/kg, i.p.) after the last dose of MOR, while prevention group received BAC (2 mg/kg, i.p.) before NAL injection. Animals were placed in the center of the EPM facing towards an open arm and recorded for 15 min. Our results showed a significant increase in the percentage of entries (p<0.05) and time (p<0.01) in the open arms of MOR withdrawn males vs control group. Conversely, the percentage of entries and time in the open arms were not modified in withdrawn females. The pretreatment with BAC did not modify the anxiety-like behavior in MOR withdrawn animals. The greater sensitivity of males in response to MOR confirms our previous observations showing a sexual dimorphism during MOR withdrawal syndrome. The lack of BAC effect suggests that the anxiety-like behavior associated to MOR withdrawal signs would not be related to the GABAergic system. Supported by UBACYT B016