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Neuropsychopharmacology Reviews (2012) 37, 307–308; doi:10.1038/npp.2011.193

Circuits, Cells, and Synapses: Toward a New Target for Deep Brain Stimulation in Depression

Fritz A Henn1

1Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA

Correspondence: Fritz A Henn, E-mail: fhenn@cshl.edu

Understanding the pathophysiology of depression requires knowledge of the anatomical pathways that malfunction in this disorder. The anatomy of depression involves limbic and hypothalamic activation mediating stress and anxiety. These interact with cortical areas, primarily the medial prefrontal cortex (mPFC), which appears to mediate the cognitive aspects of depression. The mPFC in turn innervates the thalamus and lateral habenula (l. habenula). The anatomy of melancholia has recently been advanced through an understanding of the role of the l. habenula and incorporation of this structure between the cortical and limbic inputs and the monoaminergic nuclei. The l. habenula controls the midbrain monoaminergic nuclei, whose output pathways interact with each other, as well as providing strong modulatory control of limbic and cortical areas. Recently understanding of how the dopamine system is regulated by the l. habenula in normal (Matsumoto and Hikosaka, 2009) and affectively disturbed states (Li et al, 2011) has been investigated. Over activity in the l. habenula is seen in both the learned helplessness model (Li et al, 2011) and in patients who express depressive symptoms following tryptophan depletion (Roiser et al, 2009). This over activity causes decreased dopaminergic stimuation, suppressing reward signals (Matsumoto and Hikosaka, 2009). It also depresses 5HT signals (Wang and Aghajanian, 1997), which feed back further increasing l. habenular activity. The l. habenula receives strong inputs from both the limbic system, through the basal nucleus of the stria terminalis, which carries information from the amygdala related to anxiety and from the mPFC, which may be related to the cognitive aspects of depression (Li et al, 2011) and sends its output to the midbrain aminergic nuclei.

Because it appears the l. habenula functions as a control center that regulates the reward center, modulating cortical, and limbic areas, it might be an ideal target for deep brain stimulation in cases of intractable, treatment-resistant depression. This has been utilized for a single patient and resulted in a total remission (Sartorius et al, 2010) that rapidly reversed when the stimulator was disconnected and returned after the stimulation was reinstated. The time course for the remission after initiating stimulation is slow, weeks for full remission, suggesting that structural changes underlie this effect. High frequency and high voltage stimulation inhibit l. habenula slice activity (Li et al, 2011) supporting the concept that inhibition occurs through DBS and this may well be the mechanism through which DBS acts (Figure 1).

Figure 1.
Figure 1 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Principal inputs and outputs of the l. habenula crossroad in the circuit mediating depression.

Full figure and legend (103K)Download PowerPoint slide (381 KB)

Glutaminergic over activity in the mPFC drives the over activation of the l. habenula (Li et al, 2011) in the chronically helpless line of animals, allowing the development of a depressive state mediated, in part, by altered monoaminergic function. Excess cortical glutamate in the mPFC, resulting from stress, leads to decreases in cortical synapses, a well-documented effect that can be reversed by ketamine. Chronically helpless animals show a 40% loss of synapses, suggesting enhanced stress sensitivity. The excess glutamate appears to be sustained through decreased astrocytic glutamate transporter in these learned helpless animals (Zink et al, 2010), suggesting that astrocytic dysfunction may be a fundamental step in the pathophysiology of depression.

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Conflict of interest

F Henn serves as a consultant to Astra Zeneca and is funded by the Simon's Foundation.

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References

  1. Li B, Piriz J, Mirrione M, Prulx CD, Schulz D, Henn F et al (2011). Synaptic potentiation onto habenula neurons in the learned helpless model of depression. Nature 470: 535–539. | Article | PubMed | ISI |
  2. Matsumoto M, Hikosaka O (2009). Representation of negative motivational value in the primate lateral habenula. Nat Neurosci 12: 77–84. | Article | PubMed | ISI | ChemPort |
  3. Roiser JP, Levy J, Fromm SJ, Nugent AC, Talagala Sl, Hasler G et al (2009). The effects of tryptophan depletion on neural responses to emotional words in remitted depression. Biol Psych 66: 441–450. | Article |
  4. Sartorius A, Kiening KL, Kirsch P, von Gall CC, Haberkorn U, Unterberg AW et al (2010). Remission of major depression under deep brain stimulation of the lateral habenula in a therapy refractory patient. Biol Psych 67: 9–11. | Article |
  5. Wang RY, Aghajanian GK (1997). Physiological evidence for habenula as major link between forebrain and midbrain raphe. Science 197: 89–91. | Article |
  6. Zink M, Vollmayr B, Gebieke-Harter DJ, Henn FA (2010). Reduced expression of vGLUT, EAAT2 and EAAT4 in learned helpless rats an animal model of depression. Neuropharmaclogy 58: 465–73. | Article |

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