Depression An affective disorder “affect” means emotional state or “mood”

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Nature 455:

Treated by: Electroconvulsive shock Psychotherapy Antidepressants

Animal models of depression

Deep brain stimulation of the Nucleus accumbens or the subgenual cingulate cortex decreases depression This is thought to inhibit the activity of these areas

BDNF is a neurotrophic factor that promotes neurogenesis, growth of axon branches and dendrites, and synaptogenesis Depression is associated with increased BDNF in N accumbens and VTA The Amygdala processes emotionally stressful stimuli

Stress (and depression) lowers BDNF in the hippocampus

Postmortem data from depressed humans

A human polymorphism in the pro-domain of the BDNF gene affects the packaging and release of BDNF & has different effects on different aspects of depression

Monoamine Hypothesis: Depression results from a deficit in one or both of the serotonin and norepinephrine diffuse modulatory systems.

Serotonin and Norepinephrine modulatory systems

Alternative: diathesis-stress hypothesis Diathesis means a predisposition to a disease Activation of glucocorticoid receptors in the hippocampus downregulates the hypothalamic pituitary adrenal system. A lot of maternal care in rats upregulates glucocorticoid receptors in hippocampus

There is evidence that neurogenesis in the hippocampus is important for mood regulation. Stress-induced depression down-regulates BDNF (brain-derived neurotropic factor) expression and hence down regulates neurogenesis. Antidepressants (imipramine) upregulateBDNF expression

Stress-induced dimethylation of chromatin surrounding BDNF promoter decreases expression. Antidepressant-induced acetylation upregulates expression.

5-HT1b receptors and depression

5-HT1b receptors are typically located on the presynaptic terminals of either serotonergic or other neurons. Activation of 5-HT1b receptors decreases release of 5-HT.

P11 interacts with 5-HT1b, but not other 5- HT or Dopamine receptors in a yeast two- hibrid assay

Fig. 1. Identification of an interaction between 5-HT1B receptors and p11. (A) Results from a yeast two-hybrid screen showing an interaction of p11 with the 5-HT1B receptor (left; blue color), but not with an unrelated bait (C 115; right; no color), or with pRP21, 5-HT1A, 5-HT2A, 5-HT5A, 5-HT6, D1, or D2 receptors. (B) Coimmunoprecipitation confirming that p11 interacts with (left panel) V5 epitope–tagged 5-HT1B receptors in HeLa cells and with (right panel) native 5-HT1B receptors in brain tissue from wild-type, but not p11 KO, mice. The immunoprecipitates were analyzed by Western blotting using a p11-specific antibody. The nonspecific band corresponds to the light chains of the antibodies against V5 or 5-HT1B receptors ( -V5 and - 5HT1B). (C) Immunofluorescence staining of p11 (left, red fluorescence), V5 epitope–tagged 5-HT1B receptors (middle, green fluorescence) and their colocalization (right, yellow fluorescence) at the cell surface in HeLa cells. (D) In situ hybridization made on coronal sections from a rat brain showing that the distribution of p11 mRNA is similartothatof5-HT1B receptor mRNA in (left to right) frontal cortex, ventromedial hypothalamus (arrow), hippocampus (arrow), and raphe nuclei (arrow).

Coimmunoprecipitation shows that P11 interacts with V5-tagged 5-HT1b receptors in HeLa cells and in wildtype Mouse brain (but not P11 knock-out brain).

Immunocytochemical Colocalization of P11 and 5-HT1b receptors in HeLa cells

In situ hybridization showing similar distribution of P11 and 5-HT1b mRNAs

Frontal cortex Ventromedial hypothalamus Hippocampus Raphe Nuclei

Regulation of P11 expression by antidepressant treatments and in depression like states.

The tricyclic antidepressant imipramine or electroconvulsive shock upregulate P11 mRNA

P11 mRNA was down-regulated in “depressed” mice and human brains

Non-helpless mouse Helpless Mouse Human

Fig. 2. Regulation of p11 expression by antidepressant treatments and in depression-like states. In situ hybridization illustrating an up-regulation of p11 mRNA in the forebrain following (A) repeated treatment with imipramine [10 mg/kg per day, intraperitoneally (i.p.) for 14 days] in mice (n = 8 per group) and (B) electroconvulsive therapy (ECT) for 10 days in rats (n = 5 per group). Conversely, p11 mRNA was down- regulated in (C) the forebrain in helpless H/Rouen versus nonhelpless NH/Rouen mice (n = 10 per group) and (D) in patients who suffered from unipolar major depression (n = 15 per group). Data from the anterior (A; B; C, left; D) and posterior (C, right) cingulate cortices were normalized to the corresponding controls and represent means ± SEM. *P < 0.05, ***P < versus control by Student's t test.

Over expression of P11 in Cos-7 cells increases the amount of 5-HT1b at the cell surface

Coexpression of P11 with 5-HT1b receptor enhanced the ability of serotonin to counteract the activation of adenyl cyclase by forskolin

Mice overexpressing P11 showed behavioral changes similar to antidepressant treatments: reduced thigmotaxis or immobility in a tail suspension test.

P11 knockouts have depression-like behavioral phenotypes: Increased thigmotaxis and tail-suspension induced immobility

Fig. 3. Biochemical and behavioral effects of overexpression of p11 in cells and in transgenic mice. (A) Biotinylation experiment from COS-7 cells showing that p11 increases the amount of 5-HT1B receptors at the cell surface. Data were normalized to the amount in cells transfected only with 5-HT1B receptors and represent means ± SEM for three experiments, each in triplicate. (B) The ability of serotonin (10 µM) to counteract forskolin-induced cAMP formation in COS-7 cells transfected with the 5-HT1B receptor is increased in the presence of cotransfected p11. There was no significant difference in the cAMP responses to forskolin with or without p11. Data are normalized to forskolin-stimulated conditions, with or without p11, and represent means ± SEM. Behavioral analysis on (C) thigmotaxis and (D) the tail suspension test in transgenic mice overexpressing p11 under the CamKII promoter. Black bars indicate mice with no treatment and white bars doxycycline-treated mice. Data represent means ± SEM for 10 to 18 mice per group. *P < 0.05, **P < 0.01 versus respective control by Student's t test.

P11 knockout results in less binding by 5-HT1b ligands 5ht1b antagonist binding Goes down P11KO reduces ability of 5HT to down regulate a kinase

P11 knockouts caused a loss of ability of 5-HT and the 5-HT1b agonist, anpirtoline to downregulate ERK1/2 (Fig 4c) or to decrease a PKA site phosphorylation (Fig 4D)

5-HT acting on 5-HT1b recptors in terminals of cortical glutamatergic neurons in the striatum reduced PSP amplitude in wildtype, but very little in P11 knock-outs

Since 5-HT1b receptors decrease 5-HT turnover and P11 increases this decrease, P11 knockouts increase this 5-HT turnover (Fig 4F)

But 5-HT1b antagonist decreases ultrasonic vocalization in the rat Dawson et al O6