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Acute reversible inactivation of the bed nucleus of stria terminalis induces antidepressant-like effect in the rat forced swimming test
Behavioral and Brain Functionsvolume 6, Article number: 30 (2010)
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).
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.
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.
These results suggest that acute reversible inactivation of synaptic transmission in the BNST facilitates adaptation to stress and induces antidepressant-like effects.
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 hypothalamus [1, 2]. It has extensive reciprocal connections with other limbic structures as well as with brainstem autonomic 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 stimuli [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 compromise the organism's coping mechanisms, which have been implicated in the etiology of stress-related disorders, 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 for maintaining homeostasis in response to stress. Although adaptative in nature, glucocorticoids secretion is tightly regulated since prolonged exposure to their effects can lead to serious metabolic, immune, and psychological dysfunction. Dysfunction in forebrain limbic regions that exert control over the HPA axis, such as the amygdala, hippocampus and medial prefrontal cortex (MPFC) [31, 32], has been implicated in the etiology of stress-related disorders, including PTSD and depression, which often exhibit HPA axis abnormalities [33, 34]. Substantial information from these forebrain regions are integrated in the BNST that could either excite or inhibit HPA activity depending on the region of the BNST targeted .
Failure of coping mechanisms has been recognized as a major factor precipitating depressive episodes in humans [27, 35, 36]. BNST role in stress adaptation and its connections with other limbic structures traditionally related to depression, such as the hippocampus and the MPFC, has made it a subject of study in different behavioral paradigms aimed at investigating the neurobiology of depression. In fact, the BNST is activated by stressful stimuli that induce depressive-like behavior in rodents [16, 37, 38] and this can be attenuated by systemic antidepressant-treatment , corroborating the idea that BNST dysfunction could contribute to the pathophysiology of depression. However, the studies aimed at investigating this hypothesis through local inactivation of BNST have yielded contradictory results. For example, while chemical lesions of the BNST induced antidepressant-like effects in the rat learned helplessness model [16, 19], electrolytic lesions of the BNST increased depressive-like behavior in the rat forced swimming test (FST) [39–41]. The reasons for these contradictory results are not clear, but could involve the different animal models used or methodological differences in the lesions employed (size, time of recovery or nature of the lesion - chemical versus electrical). In addition, irreversible lesions can also destroy fibers of passage and induce local plastic changes . Another disadvantage of lesion techniques is that they do not allow the identification of the precise moment when the disruption of BNST activity affects the development of the depressive-like behavior (during the pretest or during the test). Considering that BNST is interconnected with brain structures implicated in learning and memory of aversive events, such as the MPFC, the hippocampus and the amygdale , it would be interesting to investigate the participation of such cognitive mechanisms in the development of stress-induced behavioral consequences in the FST mediated by BNST.
Therefore, considering the contradictory results regarding the role of the BNST in the modulation of depressive-like behavior, and the fact that the time point of BNST influence in the FST has never been evaluated, the objective of the present study was to investigate the effects of temporary acute inactivation of synaptic transmission in the BNST, at different time points (before pretest, after pretest or before test), by local microinjection of cobalt chloride (CoCl2) in rats submitted the FST. This drug reduces calcium pre-synaptic influx  and causes a reversible inhibition of neurotransmitter release with a consequent synaptic blockage, without affecting passage fibers.
Male Wistar rats weighing 230-250 g at the beginning of each experiment were housed in pairs in a temperature-controlled room (24 ± 1°C) under standard laboratory conditions with free access to food and water and a 12 h light/12 h dark cycle (lights on at 06:30 h a.m.). Procedures were conduct in conformity with the Brazilian Society of Neuroscience and Behavior guidelines for the care and use of laboratory animals, which are in compliance with international laws and politics. The protocols described herein have been approved by the local Ethical Committee and all efforts were made to minimize animal suffering.
The following drugs were used: cobalt chloride (CoCl2; Sigma, St Louis, Missouri, USA), tribromoethanol (Aldrich, St Louis, Missouri, USA) and urethane (Sigma, St Louis, Missouri, USA). CoCl2 was dissolved in sterile artificial cerebrospinal fluid (ACSF: 100 mM NaCl; 2 mM Na3PO4; 2.5 mM KCl; 1 mM MgCl2; 27 mM NaHCO3; 2.5 mM CaCl2; pH = 7.4). Tribromoethanol and urethane were dissolved in saline 0.9%.
Stereotaxic surgery and intracerebral drug administration
Seven days before the experiment, animals were anaesthetized with tribromoethanol (250 mg/kg, i.p.) and fixed in a stereotaxic frame. After scalp anesthesia with 2% lidocaine, the skull was surgically exposed and stainless steel guide cannulae (26 G) were implanted bilaterally in the BNST using a stereotaxic apparatus (Stoelting, Wood Dale, Illinois, USA). Coordinates for cannula implantation (AP = +8.6 mm from interaural coordinate; L = +4 mm from the medial suture, V = -5.8 mm from the skull with a lateral inclination of 23°) were selected from the rat brain atlas of Paxinos and Watson . The cannulae tips were 1 mm above the site of injection and the cannulae were attached to the skull bone with stainless steel screws and acrylic cement. An obturator inside the guide cannulae prevented obstruction. After surgery, the animals received a poly-antibiotic (Pentabiotico®, Fort Dodge, Brazil), with streptomycins and penicillins, to prevent infection and a nonsteroidal anti-inflammatory, flunixine meglumine (Banamine®, Schering Plough, Brazil), for post- operation analgesia.
The needles (33G, Small Parts, Miami Lakes, FL, USA) used for microinjection into the BNST were 1 mm longer than the guide cannulae and were connected to a 2 μL syringe (7002-H, Hamilton Co., Reno, NV, USA) through PE-10 tubing. A volume of 100 nL/side was injected in 1 minute using an infusion pump (Kd Scientific, Holliston, MA, USA). The movement of an air bubble inside the polyethylene catheter confirmed drug flow.
Forced swimming test (FST)
The procedures for the FST, a widely used behavioral test for the detection of antidepressant-like effects, were similar to those described earlier [45–48]. Animals were initially placed individually to swim in plastic cylinders (30 cm of diameter by 40 cm in height containing 25 cm of water at 24 ± 1°C  for 15 min (pretest). They were then removed and allowed to dry in a separate cage before returning to their home cages. Twenty-four hours later the animals were submitted to a 5 min session of forced swimming session (test). During this session the total amount of time in which animals remained immobile (except for small limb movements necessary for floating) were recorded by an observer that was blind to the treatments. The water was changed after each trial to avoid the influence of alarm substances.
Open field test
Independent groups of animals were submitted to the open field test in order to investigate if the treatments used induced any significant motor effect, which would interfere in the FST results. The animals were placed individually in the center of an open circular arena (72 cm in diameter with a 50 cm high Plexiglas wall) located in a sound-attenuated, temperature-controlled room, illuminated with three 40W fluorescent bulbs. The animals were left in the arena for 10 minutes. Their exploratory activity was videotaped and the behavioral analysis was blindly performed with the help of the Ethovision software (version 1.9; Noldus, the Netherlands). This software detects the position of the animal in the open arena and calculates the distance moved.
After the behavioral tests, animals were anesthetized with urethane (1.25 g/kg, i.p.) and then 100 nl of 1% Evan's blue dye was injected into the BST as a marker of injection site. Following that, they were perfused through the left ventricle of the heart with isotonic saline followed by 10% formalin solution. The brains were removed and after a minimum period of 3 days immersed in a 10% formalin solution, 40 μm sections were obtained in a Cryostat (Cryocut 1800). The injection sites were identified on diagrams from the Paxinos and Watson's atlas . Rats that had received injections outside the aimed area were excluded from analysis.
Experiment 1: effects of CoCl2 injection into the BNST of rats submitted to the FST
Animals were randomly assigned to three independent groups which received bilateral injection into the BNST of either 100 nL of vehicle (ACSF)  or 1 mM/100 nL of CoCl2 [10, 51] and were submitted to FST. The first group of animals received the microinjections into the BNST 10 minutes before the pretest session (ACSF: n = 5 and CoCl2: n = 6). The second group received the microinjections into the BNST immediately after the end of pretest session (ACSF: n = 6 and CoCl2: n = 6). Finally, the third group received the microinjections into the BNST 10 minutes before the test session (ACSF: n = 6 and CoCl2: n = 7). Additional groups received the microinjections into structures surrounding the BNST before the pretest (ACSF: n = 4 and CoCl2: n = 3) or before the test (ACSF: n = 3 and CoCl2: n = 5).
Experiment 2: effects of CoCl2 injection into the BNST of rats submitted to the open field test
The results of the FST and from open-field test were analyzed using unpaired Student-t test. Probability less than 0.05 was accepted as significant.
Determination of microinjection sites
A representative photomicrograph of a coronal brain section depicting bilateral microinjection sites in the BST of one representative animal is presented in Figure 1. Moreover, diagrammatic representation showing microinjection sites of ACSF and CoCl2 into the BNST and in structures surrounding the BNST are also shown in Figure 1.
Experiment one: effects of CoCl2 injection into the BNST of rats submitted to the FST
Injection of CoCl2 into the BNST before the pretest (170 ± 21 vs 46 ± 13 s, t9 = 5.024, P < 0.001) or the test (182 ± 20 vs 111 ± 17 s, t10 = 2.627, P < 0.05) sessions induced a significant reduction of immobility time in the FST (Figure 2). There was no significant statistical difference between vehicle and CoCl2-treated groups that received the injection into the BNST immediately after the pretest (167 ± 17 vs 148 ± 33 s, t10 = 2.627, P < 0.05) (Figure 2). Immobility time obtained in animals that received CoCl2 before the pretest or before the test was significantly different (t11 = 2.9, P < 0.05). Injection of CoCl2 into structures surrounding the BNST, such as anterior commissure, internal capsule or fornix, before the pretest (173 ± 11 vs 182 ± 23 s, t5 = 0.385, P > 0.05) or the test (189 ± 19 vs 162 ± 12 s, t6 = 1.244, P > 0.05) did not affect immobility time in the FST.
Experiment two: effects of CoCl2 injection into the BNST of rats submitted to the open field test
Analysis of total distance travelled in the open-field test did not show a significant effect of BNST treatment with CoCl2 (14 ± 2 vs 15 ± 3 m, t10 = 0.27, P > 0.05), when compared with animals treated with vehicle (Figure 3).
The FST is probably the most frequently used animal model predictive of antidepressant activity . It is based on the observation that rodents exposed to an enclosed cylinder filled with water perform escape oriented behaviors for few minutes and, afterwards, assume a posture of immobility which is of shorter duration in animals that had received antidepressant treatment [45, 47, 48]. In the present study, the results showed that intra-BNST injection of CoCl2 decreased the immobility time in this model when microinjected before pretest or before test, whereas treatment after pretest did not have any effect. These effects do not rely on unspecific motor changes, since CoCl2 administration into the BNST did not modify animal's locomotor activity in the open field test. Therefore, these results are indicative of an antidepressant-like effect induced by transient blockage of synaptic transmission in the BNST during the pretest or test sessions in the rats submitted to the FST.
Contradictory results regarding BNST role in animal models of depression have been previously described [39–41]. It has been reported, for example, that chronic electrolytic lesion of the BNST increases rather than decreases the behavioral consequences produced by the FST [38–40]. However, chronic electrolytic lesion destroy not only intrinsic BNST neurons, but also fibers of passage that project through it on their way to other structures. On the other hand, chemical lesions of the BNST, which spares fibers of passage, induced antidepressant-like effects in the rat learned helplessness model of depression . The present study, by inducing a reversible inactivation of synaptic transmission that spares fibers of passage, corroborates the previous results in the learned helplessness model and suggests that this experimental approach (CoCl2-induced inactivation) could be more useful to unveil the specific role of BNST neurons in FST model.
It should be noticed, however, that inconsistent findings regarding BNST participation in the modulation of depressive-like behaviors could be related to the fact that BNST is a cluster of 12 nuclei, which can be divided into anterior and posterior subdivisions, each containing several nuclei, which differ in their projection pattern and neurochemical identity . In this regard, depending on the extension of the lesion or the drug distribution into BNST, different portions of it could have been affected in different studies, thus allowing the occurrence of contradictory behavioral effects in the FST.
The BNST has long been recognized as an important structure that integrates and mediates emotional, cognitive, autonomic, endocrine and behavioral responses to stress [2, 6, 9, 10, 14, 20, 51, 53]. Lesions as well as pre-test infusions into the BNST of compounds that disrupt its function reduce behavioral and autonomic responses to stress [10, 16, 51, 54, 55]. This is especially evident in paradigms in which behavior is influenced by long-duration stimuli and in paradigms that assess the persistent behavioral effects of even a brief stressor, but that are severe and unpredictable, such inescapable shocks . Corroborating this proposal, the BNST is activated in response to several aversive stimuli [15–18] including inescapable shock exposure . BNST stimulation, on the other hand, produces behavioral consequences similar to those induced by forced restraint  whereas its chemical lesion prevents the development of behavioral deficits that characterize the "learned helplessness" phenomenon . These deficits are thought to arise from increased fear and anxiety produced by the previous exposure to inescapable shocks [56, 57]. Finally, blockade of BNST noradrenergic transmission attenuates immobilization stress-induced anxiogenic-like effects [54, 55, 58].
Taken together, these pieces of evidence indicate that activation of BNST during stress could contribute to the development of stress-induced behavioral consequences, thus impairing adaptation in a subsequent stressful situation. In this way, BNST activation during stress pre-exposure could facilitate a hyperanxiety state that would impair adaptation to a subsequent stress exposure. This is supported, for example, by the observation that the positive effects of BNST lesions in the learned helplessness model are due to a reduction in the anxiogenic effects of pre-exposure to the inescapable shocks . Moreover, behavioral manipulation that prevents learned helplessness development also reduces the anxiogenic effect and the increased BNST Fos expression caused by the previous exposure to inescapable shocks . Finally, stress-induced hyperanxiety have been shown to occur in association to structural and functional changes in BNST [21–24], thus supporting the involvement of this nucleus in mechanisms of stress-induced emotional consequences.
Failure to coping with stress is an important precipitating factor in depressive illnesses [27, 35, 36] and antidepressants promote behavioral adaptation to stress . In this context, blockade of synaptic transmission within the BNST before pre-test could reduce the stress-induced behavioral outcomes (e.g. hyperanxiety) and, thus, facilitate adaptation to the subsequent stress section, inducing antidepressant-like effects . Moreover, considering that BNST is uniquely positioned to receive emotional and learning associated informations and to integrate these into the reward/motivation circuitry , its inactivation before the test might have induced antidepressant-like effect by increasing motivation and goal-directed behavior to aimed at performing escape from the swimming stress.
It could also be speculated that the reduced immobility observed during the test could have been a consequence of learning and memory impairments induced by BSNT inactivation during pre-test and test, respectively. However, previous results from the literature showed that BNST lesions did not impair navigational learning and memory in the Morris water Maze , thus questioning the aforementioned suggestion. Despite that, the antidepressant-like effect reported after BNST blockage in the present study cannot be completely dissociated from effects in the cognitive performance. In fact, cognitive mechanisms have been implicated in the neurobiology of depression and antidepressant response, since they might interfere with stress adaptation and biases in the processing of negative affect .
Finally, it can be speculated that the deleterious effects of stress could also be mediated, at least in part, by dysregulation (e.g., overactivation) of the HPA axis . Activation of the HPA axis is a primary mechanism for maintaining homeostasis in response to stress. Neurons in the paraventricular nucleus of the hypothalamus (PVN) synthesize corticotropin-releasing hormone (CRH), which is released into the hypophysial portal system and trigger adrenocorticotropin (ACTH) secretion from the anterior pituitary. ACTH stimulates the secretion of glucocorticoids from the adrenals into the circulation to mobilize energy stores, maintain blood pressure, and exert negative feedback at the HPA brain and pituitary sites (for review, see ). Glucocorticoids secretion needs to be tightly regulated since prolonged exposure to their effects can lead to serious metabolic, immune, and psychological dysfunction. The BNST has a central role in controlling HPA axis activity [6, 28, 30], which can be dysfunctional in depression [31–34]. Considering that glucocorticoids facilitate whereas adrenalectomy impairs the expression of the depressive-like behavior in the FST [62–64], it is also possible that BSNT inactivation might have attenuated HPA axis activation in response to stress, and the consequent reduction in the glucocorticoid levels could have contributed to the reduced expression of the depressive-like behavior in the FST. This hypothesis, however, warrants further investigation.
Considering that distinct neurobiological mechanisms can be involved in the different experimental procedures used to study the neurobiology of depression, the hypothesis discussed herein should be further tested in other animal models of depression with higher face validity than the FST.
In conclusion, stress-induced BNST activation could promote a bias in the processing of threatening cues which could render the animal more susceptible to the development of behavioral consequences of stress. On the other hand, BNST inactivation before stress could protect animals against emotional changes caused by previous stressful stimuli presentation, perhaps by facilitating mechanisms involved in the ability to cope with a new stressful situation. Further studies are necessary to characterize the neurotransmitters involved in these effects.
artificial cerebrospinal fluid
bed nucleus of the stria terminalis
forced swimming test
medial prefrontal córtex
paraventricular nucleus of the hypothalamus
posttraumatic stress disorder.
Dong HW, Petrovich GD, Watts AG, Swanson LW: Basic organization of projections from the oval and fusiform nuclei of the bed nuclei of the stria terminalis in adult rat brain. J Comp Neurol. 2001, 436 (4): 430-455. 10.1002/cne.1079.
Forray MI, Gysling K: Role of noradrenergic projections to the bed nucleus of the stria terminalis in the regulation of the hypothalamic-pituitary-adrenal axis. Brain Res Brain Res Rev. 2004, 47 (1-3): 145-160. 10.1016/j.brainresrev.2004.07.011.
Martin LJ, Powers RE, Dellovade TL, Price DL: The bed nucleus-amygdala continuum in human and monkey. J Comp Neurol. 1991, 309 (4): 445-485. 10.1002/cne.903090404.
Shin JW, Geerling JC, Loewy AD: Inputs to the ventrolateral bed nucleus of the stria terminalis. J Comp Neurol. 2008, 511 (5): 628-657. 10.1002/cne.21870.
Walker DL, Toufexis DJ, Davis M: Role of the bed nucleus of the stria terminalis versus the amygdala in fear, stress, and anxiety. Eur J Pharmacol. 2003, 463 (1-3): 199-216. 10.1016/S0014-2999(03)01282-2.
Choi DC, Furay AR, Evanson NK, Ostrander MM, Ulrich-Lai YM, Herman JP: Bed nucleus of the stria terminalis subregions differentially regulate hypothalamic-pituitary-adrenal axis activity: implications for the integration of limbic inputs. J Neurosci. 2007, 27 (8): 2025-2034. 10.1523/JNEUROSCI.4301-06.2007.
Crestani CC, Alves FH, Resstel LB, Correa FM: Cardiovascular effects of noradrenaline microinjection in the bed nucleus of the stria terminalis of the rat brain. J Neurosci Res. 2007, 85 (7): 1592-1599. 10.1002/jnr.21250.
Crestani CC, Alves FH, Resstel LB, Correa FM: Both alpha1 and alpha2-adrenoceptors mediate the cardiovascular responses to noradrenaline microinjected into the bed nucleus of the stria terminal of rats. Br J Pharmacol. 2008, 153 (3): 583-590. 10.1038/sj.bjp.0707591.
Herman JP, Ostrander MM, Mueller NK, Figueiredo H: Limbic system mechanisms of stress regulation: hypothalamo-pituitary-adrenocortical axis. Prog Neuropsychopharmacol Biol Psychiatry. 2005, 29 (8): 1201-1213. 10.1016/j.pnpbp.2005.08.006.
Resstel LB, Alves FH, Reis DG, Crestani CC, Correa FM, Guimaraes FS: Anxiolytic-like effects induced by acute reversible inactivation of the bed nucleus of stria terminalis. Neuroscience. 2008, 154 (3): 869-876. 10.1016/j.neuroscience.2008.04.007.
Alves FH, Crestani CC, Resstel LB, Correa FM: Cardiovascular effects of carbachol microinjected into the bed nucleus of the stria terminalis of the rat brain. Brain Res. 2007, 1143: 161-168. 10.1016/j.brainres.2007.01.057.
Crestani CC, Busnardo C, Tavares RF, Alves FH, Correa FM: Involvement of hypothalamic paraventricular nucleus non-N-methyl-d-aspartate receptors in the pressor response to noradrenaline microinjected into the bed nucleus of the stria terminalis of unanesthetized rats. Eur J Neurosci. 2009, 29 (11): 2166-2176. 10.1111/j.1460-9568.2009.06762.x.
Crestani CC, Alves FH, Resstel LB, Correa FM: Bed nucleus of the stria terminalis alpha(1)-adrenoceptor modulates baroreflex cardiac component in unanesthetized rats. Brain Res. 2008, 1245: 108-115. 10.1016/j.brainres.2008.09.082.
Casada JH, Dafny N: Restraint and stimulation of bed nucleus of the stria terminalis produce similar stress-like behaviors. Brain Res Bull. 1991, 27 (2): 207-212. 10.1016/0361-9230(91)90069-V.
Beijamini V, Guimaraes FS: c-Fos expression increase in NADPH-diaphorase positive neurons after exposure to a live cat. Behav Brain Res. 2006, 170 (1): 52-61. 10.1016/j.bbr.2006.01.025.
Greenwood BN, Foley TE, Burhans D, Maier SF, Fleshner M: The consequences of uncontrollable stress are sensitive to duration of prior wheel running. Brain Res. 2005, 1033 (2): 164-178. 10.1016/j.brainres.2004.11.037.
Ma S, Morilak DA: Induction of FOS expression by acute immobilization stress is reduced in locus coeruleus and medial amygdala of Wistar-Kyoto rats compared to Sprague-Dawley rats. Neuroscience. 2004, 124 (4): 963-972. 10.1016/j.neuroscience.2003.12.028.
Valles A, Marti O, Armario A: Long-term effects of a single exposure to immobilization: a c-fos mRNA study of the response to the homotypic stressor in the rat brain. J Neurobiol. 2006, 66 (6): 591-602. 10.1002/neu.20252.
Hammack SE, Richey KJ, Watkins LR, Maier SF: Chemical lesion of the bed nucleus of the stria terminalis blocks the behavioral consequences of uncontrollable stress. Behav Neurosci. 2004, 118 (2): 443-448. 10.1037/0735-7044.118.2.443.
Treit D, Aujla H, Menard J: Does the bed nucleus of the stria terminalis mediate fear behaviors?. Behav Neurosci. 1998, 112 (2): 379-386. 10.1037/0735-7044.112.2.379.
Blundell J, Adamec R: The NMDA receptor antagonist CPP blocks the effects of predator stress on pCREB in brain regions involved in fearful and anxious behavior. Brain Res. 2007, 1136 (1): 59-76. 10.1016/j.brainres.2006.09.078.
Hammack SE, Cheung J, Rhodes KM, Schutz KC, Falls WA, Braas KM, May V: Chronic stress increases pituitary adenylate cyclase-activating peptide (PACAP) and brain-derived neurotrophic factor (BDNF) mRNA expression in the bed nucleus of the stria terminalis (BNST): roles for PACAP in anxiety-like behavior. Psychoneuroendocrinology. 2009, 34 (6): 833-843. 10.1016/j.psyneuen.2008.12.013.
Pego JM, Morgado P, Pinto LG, Cerqueira JJ, Almeida OF, Sousa N: Dissociation of the morphological correlates of stress-induced anxiety and fear. Eur J Neurosci. 2008, 27 (6): 1503-1516. 10.1111/j.1460-9568.2008.06112.x.
Vyas A, Bernal S, Chattarji S: Effects of chronic stress on dendritic arborization in the central and extended amygdala. Brain Res. 2003, 965 (1-2): 290-294. 10.1016/S0006-8993(02)04162-8.
Nemeroff CB, Bremner JD, Foa EB, Mayberg HS, North CS, Stein MB: Posttraumatic stress disorder: a state-of-the-science review. J Psychiatr Res. 2006, 40 (1): 1-21. 10.1016/j.jpsychires.2005.07.005.
Olff M, Langeland W, Gersons BP: The psychobiology of PTSD: coping with trauma. Psychoneuroendocrinology. 2005, 30 (10): 974-982. 10.1016/j.psyneuen.2005.04.009.
Southwick SM, Vythilingam M, Charney DS: The psychobiology of depression and resilience to stress: implications for prevention and treatment. Annu Rev Clin Psychol. 2005, 1: 255-291. 10.1146/annurev.clinpsy.1.102803.143948.
Choi DC, Furay AR, Evanson NK, Ulrich-Lai YM, Nguyen MM, Ostrander MM, Herman JP: The role of the posterior medial bed nucleus of the stria terminalis in modulating hypothalamic-pituitary-adrenocortical axis responsiveness to acute and chronic stress. Psychoneuroendocrinology. 2008, 33 (5): 659-669. 10.1016/j.psyneuen.2008.02.006.
Jankord R, Herman JP: Limbic regulation of hypothalamo-pituitary-adrenocortical function during acute and chronic stress. Ann N Y Acad Sci. 2008, 1148: 64-73. 10.1196/annals.1410.012.
Morilak DA, Barrera G, Echevarria DJ, Garcia AS, Hernandez A, Ma S, Petre CO: Role of brain norepinephrine in the behavioral response to stress. Prog Neuropsychopharmacol Biol Psychiatry. 2005, 29 (8): 1214-1224. 10.1016/j.pnpbp.2005.08.007.
Koenigs M, Grafman J: The functional neuroanatomy of depression: distinct roles for ventromedial and dorsolateral prefrontal cortex. Behav Brain Res. 2009, 201 (2): 239-243. 10.1016/j.bbr.2009.03.004.
Pittenger C, Duman RS: Stress, depression, and neuroplasticity: a convergence of mechanisms. Neuropsychopharmacology. 2008, 33 (1): 88-109. 10.1038/sj.npp.1301574.
de Kloet CS, Vermetten E, Geuze E, Kavelaars A, Heijnen CJ, Westenberg HG: Assessment of HPA-axis function in posttraumatic stress disorder: pharmacological and non-pharmacological challenge tests, a review. J Psychiatr Res. 2006, 40 (6): 550-567. 10.1016/j.jpsychires.2005.08.002.
Pariante CM, Lightman SL: The HPA axis in major depression: classical theories and new developments. Trends Neurosci. 2008, 31 (9): 464-468. 10.1016/j.tins.2008.06.006.
Kendler KS, Kessler RC, Walters EE, MacLean C, Neale MC, Heath AC, Eaves LJ: Stressful life events, genetic liability, and onset of an episode of major depression in women. Am J Psychiatry. 1995, 152 (6): 833-842.
Post RM: Transduction of psychosocial stress into the neurobiology of recurrent affective disorder. Am J Psychiatry. 1992, 149 (8): 999-1010.
Muigg P, Hoelzl U, Palfrader K, Neumann I, Wigger A, Landgraf R, Singewald N: Altered brain activation pattern associated with drug-induced attenuation of enhanced depression-like behavior in rats bred for high anxiety. Biol Psychiatry. 2007, 61 (6): 782-796. 10.1016/j.biopsych.2006.08.035.
Stone EA, Lehmann ML, Lin Y, Quartermain D: Depressive behavior in mice due to immune stimulation is accompanied by reduced neural activity in brain regions involved in positively motivated behavior. Biol Psychiatry. 2006, 60 (8): 803-811. 10.1016/j.biopsych.2006.04.020.
Pezuk P, Aydin E, Aksoy A, Canbeyli R: Effects of BNST lesions in female rats on forced swimming and navigational learning. Brain Res. 2008, 1228: 199-207. 10.1016/j.brainres.2008.06.071.
Pezuk P, Goz D, Aksoy A, Canbeyli R: BNST lesions aggravate behavioral despair but do not impair navigational learning in rats. Brain Res Bull. 2006, 69 (4): 416-421. 10.1016/j.brainresbull.2006.02.008.
Schulz D, Canbeyli RS: Lesion of the bed nucleus of the stria terminalis enhances learned despair. Brain Res Bull. 2000, 52 (2): 83-87. 10.1016/S0361-9230(00)00235-5.
Rangel A, Gonzalez LE, Villarroel V, Hernandez L: Anxiolysis followed by anxiogenesis relates to coping and corticosterone after medial prefrontal cortical damage in rats. Brain Res. 2003, 992 (1): 96-103. 10.1016/j.brainres.2003.08.038.
Jalabert M, Aston-Jones G, Herzog E, Manzoni O, Georges F: Role of the bed nucleus of the stria terminalis in the control of ventral tegmental area dopamine neurons. Prog Neuropsychopharmacol Biol Psychiatry. 2009, 33 (8): 1336-1346. 10.1016/j.pnpbp.2009.07.010.
Kretz R: Local cobalt injection: a method to discriminate presynaptic axonal from postsynaptic neuronal activity. J Neurosci Methods. 1984, 11 (2): 129-135. 10.1016/0165-0270(84)90030-X.
Cryan JF, Markou A, Lucki I: Assessing antidepressant activity in rodents: recent developments and future needs. Trends Pharmacol Sci. 2002, 23 (5): 238-245. 10.1016/S0165-6147(02)02017-5.
Cryan JF, Valentino RJ, Lucki I: Assessing substrates underlying the behavioral effects of antidepressants using the modified rat forced swimming test. Neurosci Biobehav Rev. 2005, 29 (4-5): 547-569. 10.1016/j.neubiorev.2005.03.008.
Porsolt RD, Anton G, Blavet N, Jalfre M: Behavioural despair in rats: a new model sensitive to antidepressant treatments. Eur J Pharmacol. 1978, 47 (4): 379-391. 10.1016/0014-2999(78)90118-8.
Porsolt RD, Le Pichon M, Jalfre M: Depression: a new animal model sensitive to antidepressant treatments. Nature. 1977, 266 (5604): 730-732. 10.1038/266730a0.
Joca SR, Guimaraes FS: Inhibition of neuronal nitric oxide synthase in the rat hippocampus induces antidepressant-like effects. Psychopharmacology (Berl). 2006, 185 (3): 298-305. 10.1007/s00213-006-0326-2.
Paxinos G, Watson C: The rat brain in stereotaxic coordinates. 1997, Sidney Australia Academic Press, 3
Crestani CC, Alves FH, Tavares RF, Correa FM: Role of the bed nucleus of the stria terminalis in the cardiovascular responses to acute restraint stress in rats. Stress. 2009, 12 (3): 268-278. 10.1080/10253890802331477.
Dumont EC: What is the bed nucleus of the stria terminalis?. Prog Neuropsychopharmacol Biol Psychiatry. 2009, 33 (8): 1289-1290. 10.1016/j.pnpbp.2009.07.006.
Alves FH, Crestani CC, Resstel LB, Correa FM: Bed nucleus of the stria terminalis N-methyl-D-aspartate receptors and nitric oxide modulate the baroreflex cardiac component in unanesthetized rats. J Neurosci Res. 2009, 87 (7): 1703-1711. 10.1002/jnr.21974.
Cecchi M, Khoshbouei H, Javors M, Morilak DA: Modulatory effects of norepinephrine in the lateral bed nucleus of the stria terminalis on behavioral and neuroendocrine responses to acute stress. Neuroscience. 2002, 112 (1): 13-21. 10.1016/S0306-4522(02)00062-3.
Khoshbouei H, Cecchi M, Morilak DA: Modulatory effects of galanin in the lateral bed nucleus of the stria terminalis on behavioral and neuroendocrine responses to acute stress. Neuropsychopharmacology. 2002, 27 (1): 25-34. 10.1016/S0893-133X(01)00424-9.
Maier SF: Role of fear in mediating shuttle escape learning deficit produced by inescapable shock. J Exp Psychol Anim Behav Process. 1990, 16 (2): 137-149. 10.1037/0097-7403.16.2.137.
Maier SF, Grahn RE, Kalman BA, Sutton LC, Wiertelak EP, Watkins LR: The role of the amygdala and dorsal raphe nucleus in mediating the behavioral consequences of inescapable shock. Behav Neurosci. 1993, 107 (2): 377-388. 10.1037/0735-7044.107.2.377.
Morilak DA, Cecchi M, Khoshbouei H: Interactions of norepinephrine and galanin in the central amygdala and lateral bed nucleus of the stria terminalis modulate the behavioral response to acute stress. Life Sci. 2003, 73 (6): 715-726. 10.1016/S0024-3205(03)00392-8.
Sherman AD, Sacquitne JL, Petty F: Specificity of the learned helplessness model of depression. Pharmacol Biochem Behav. 1982, 16 (3): 449-454. 10.1016/0091-3057(82)90451-8.
Graeff FG, Guimaraes FS, De Andrade TG, Deakin JF: Role of 5-HT in stress, anxiety, and depression. Pharmacol Biochem Behav. 1996, 54 (1): 129-141. 10.1016/0091-3057(95)02135-3.
Sapolsky RM: Stress and plasticity in the limbic system. Neurochem Res. 2003, 28 (11): 1735-1742. 10.1023/A:1026021307833.
Jefferys D, Funder J: Nitric oxide modulates retention of immobility in the forced swimming test in rats. Eur J Pharmacol. 1996, 295 (2-3): 131-135. 10.1016/0014-2999(95)00655-9.
Jefferys D, Funder JW: The forced swimming test: effects of glucose administration on the response to food deprivation and adrenalectomy. Eur J Pharmacol. 1991, 205 (3): 267-269. 10.1016/0014-2999(91)90908-9.
Veldhuis HD, De Korte CC, De Kloet ER: Glucocorticoids facilitate the retention of acquired immobility during forced swimming. Eur J Pharmacol. 1985, 115 (2-3): 211-217. 10.1016/0014-2999(85)90693-4.
The authors wish to thank I.A.C. Fortunato, I.I.B. Aguiar and S.S. Guilhaume for technical assistance and Dr. Resstel for the comments in the decision to submit the manuscript for publication. C.C.C. has a postdoctoral fellowships from CNPq (150295/2010-3) and F.H.F.A. has a Ph.D. fellowship from CNPq (870307/1997-5). This research was supported by grants from FAEPA, FAPESP and CNPq.
The authors declare that they have no competing interests.
C.C.C. and S.R.L.J. contributed to the conception and design of the study. Moreover, S.R.L.J. was responsible by analysis and interpretation of data, drafted the manuscript and continuously supervised the study. C.C.C. and F.H.F.A. were responsible for data collection and helped to draft the manuscript. F.S.G. and F.M.A.C. helped to draft the manuscript and continuously supervised the study. All authors read and approved the final manuscript.