Elsevier

Neuroscience

Volume 154, Issue 3, 26 June 2008, Pages 869-876
Neuroscience

Behavioural neuroscience
Anxiolytic-like effects induced by acute reversible inactivation of the bed nucleus of stria terminalis

https://doi.org/10.1016/j.neuroscience.2008.04.007Get rights and content

Abstract

There is conflicting evidence concerning the role of the bed nucleus of the stria terminalis (BNST) in fear and anxiety-elicited behavior. Most of the studies investigating this role, however, employed irreversible lesions of this nucleus. The objective of the present study was to investigate the effects of an acute and reversible inactivation of the BNST in rats submitted to the Vogel conflict test (VCT) and contextual fear conditioning, two widely employed animal models that are responsive to prototypal anxiolytic drugs. Male Wistar rats were submitted to stereotaxic surgery to bilaterally implant cannulae into the BNST. Ten minutes before the test they received bilateral microinjections of cobalt chloride (CoCl2) (1 mM/100 nL), a nonselective synapse blocker. CoCl2 produced anxiolytic-like effects in tests, increasing the number of punished licks in the VCT and decreasing freezing behavior and the increase in mean arterial blood pressure and heart rate of animals re-exposed to the context where they had received electrical foot shocks 24 h before. The results indicate that the BNST is engaged in behavioral responses elicited by punished stimuli and aversively conditioned contexts, reinforcing its proposed role in anxiety.

Section snippets

Animal preparation

Male Wistar rats weighing 230–270 g were used. Animals were kept in the Animal Care Unit of the Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo. Rats were housed individually in plastic cages with free access to food and water under a 12-h light/dark cycle (lights on at 06:30 h). The Institution's Animal Ethics Committee approved the housing conditions and experimental procedures (process number: 215-2005). Procedures were conducted in conformity with

Results

Diagrammatic representations showing the bilateral injection sites in the BNST and surrounding structures and a representative photomicrograph are presented in Fig. 1.

Discussion

The VCT is a widely used animal model of anxiety based on the suppression of punished responses. In this model, anxiolytic drugs typically increase the number of punished, but not of unpunished responses (Millan and Brocco, 2003). In the present study we showed that an acute and selective inhibition of synaptic transmission in the BNST caused similar effects, increasing the number of punished without changing the number of unpunished licks. Moreover, this treatment did not change nociceptive

Conclusion

In conclusion, the present results suggest that the putative functional differences between the BNST and the amygdala should be re-evaluated. They confirm, however, the involvement of the BNST in defensive responses evoked by aversive stimuli and indicate that more investigation is needed to unveil its precise role in these responses.

Acknowledgments

The authors wish to thank Ivanilda A. C. Fortunato and José Carlos Aguiar for technical help. Financial support from FAPESP and CNPq.

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