Acute reversible inactivation of the bed nucleus of stria terminalis induces antidepressant-like effect in the rat forced swimming test.
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 (CoCl2) 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 CoCl2 (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
CoCl2 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 CoCl2 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.


CONCLUSIONS
These results suggest that acute reversible inactivation of synaptic transmission in the BNST facilitates adaptation to stress and induces antidepressant-like effects.
Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil.
Carlos C
CC
Crestani
Fernando H F
FH
Alves
Fernando M A
FM
Correa
Francisco S
FS
Guimarães
Sâmia R L
SR
Joca
D000223:Adaptation, Psychological / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D003035:Cobalt / Q000494:pharmacology*; D003863:Depression / Q000503:physiopathology / Q000517:prevention & control*; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D008297:Male; D008845:Microinjections; D051381:Rats; D017208:Rats, Wistar; D012686:Septal Nuclei / Q000187:drug effects* / Q000502:physiology*; D013550:Swimming
D000928:Antidepressive Agents; D003035:Cobalt; C018021:cobaltous chloride