Crestani et al. Behavioral and Brain Functions 2010, 6:30 http://www.behavioralandbrainfunctions.com/content/6/1/30 Open Access RESEARCH © 2010 Crestani et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Research Acute reversible inactivation of the bed nucleus of stria terminalis induces antidepressant-like effect in the rat forced swimming test Carlos C Crestani 1 , Fernando HF Alves 1 , Fernando MA Correa 1 , Francisco S Guimarães 1 and Sâmia RL Joca* 2 Abstract Background: The bed nucleus of stria terminalis (BNST) is a limbic forebrain structure involved in hypothalamo- pituitary-adrenal axis regulation and stress adaptation. Inappropriate adaptation to stress is thought to compromise the organism's coping mechanisms, which have been implicated in the neurobiology of depression. However, the studies aimed at investigating BNST involvement in depression pathophysiology have yielded contradictory results. Therefore, the objective of the present study was to investigate the effects of temporary acute inactivation of synaptic transmission in the BNST by local microinjection of cobalt chloride (CoCl 2 ) in rats subjected to the forced swimming test (FST ). Methods: Rats implanted with cannulae aimed at the BNST were submitted to 15 min of forced swimming (pretest). Twenty-four hours later immobility time was registered in a new 5 min forced swimming session (test). Independent groups of rats received bilateral microinjections of CoCl 2 (1 mM/100 nL) before or immediately after pretest or before the test session. Additional groups received the same treatment and were submitted to the open field test to control for unspecific effects on locomotor behavior. Results: CoCl 2 injection into the BNST before either the pretest or test sessions reduced immobility in the FST, suggesting an antidepressant-like effect. No significant effect of CoCl 2 was observed when it was injected into the BNST immediately after pretest. In addition, no effect of BNST inactivation was observed in the open field test. Conclusion: These results suggest that acute reversible inactivation of synaptic transmission in the BNST facilitates adaptation to stress and induces antidepressant-like effects. Background The bed nucleus of stria terminalis (BNST) is a limbic forebrain structure situated ventrally to the lateral septal nucleus and dorsally to the preoptic area of the hypothal- amus [1,2]. It has extensive reciprocal connections with other limbic structures as well as with brainstem auto- nomic nuclei [2-5], and it is an import relay station for the integration of information from brain regions associated with the control of emotional, cognitive, autonomic, endocrine and behavioral responses [2,6-13]. Several studies have suggested that the BNST mediates behavioral responses to acute and chronic aversive stim- uli [5,14]. This is supported by reports that the BNST is activated in response to stress [15-18] and modulates anxiety-related behaviors in several animal models [5,10,19,20]. Moreover, the BNST could also mediate behavioral adaptation to chronic stress exposure [21-24]. Inappropriate adaptation to stress is thought to compro- mise the organism's coping mechanisms, which have been implicated in the etiology of stress-related disor- ders, such as posttraumatic stress disorder (PTSD) and depression [25-27]. BNST involvement in the activation and termination of the hypothalamo-pituitary-adrenal (HPA) axis response to stress has been well documented in the literature [6,28- 30]. Activation of the HPA axis is a primary mechanism * Correspondence: samia@usp.br 2 Laboratory of Pharmacology, Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto; University of São Paulo, 14040-903, Ribeirão Preto, SP, Brazil Full list of author information is available at the end of the article