The pharmacology of antidepressants is not entirely clear.
The earliest and probably most widely accepted scientific theory of antidepressant action is the monoamine hypothesis (which can be traced back to the 1950s), which states that depression is due to an imbalance (most often a deficiency) of the monoamine neurotransmitters (namely serotonin, norepinephrine and dopamine). [1] It was originally proposed based on the observation that certain hydrazine anti-tuberculosis agents produce antidepressant effects, which was later linked to their inhibitory effects on monoamine oxidase, the enzyme that catalyses the breakdown of the monoamine neurotransmitters. [1] All antidepressants that have entered the market before 2011 have the monoamine hypothesis as their theoretical basis, with the possible exception of agomelatine which acts on a dual melatonergic-serotonergic pathway. [1]
Despite the success of the monoamine hypothesis it has a number of limitations: for one, all monoaminergic antidepressants have a delayed onset of action of at least a week; and secondly, there are a sizeable portion (>40%) of depressed patients that do not adequately respond to monoaminergic antidepressants. [2] [3] Further evidence to the contrary of the monoamine hypothesis are the recent findings that a single intravenous infusion with ketamine, an antagonist of the NMDA receptor — a type of glutamate receptor — produces rapid (within 2 hours), robust and sustained (lasting for up to a fortnight) antidepressant effects. [3] Monoamine precursor depletion also fails to alter mood. [4] [5] [6] To overcome these flaws with the monoamine hypothesis a number of alternative hypotheses have been proposed, including the glutamate, neurogenic, epigenetic, cortisol hypersecretion and inflammatory hypotheses. [2] [3] [7] [8] Another hypothesis that has been proposed which would explain the delay is the hypothesis that monoamines don't directly influence mood, but influence emotional perception biases. [9]
In 1965, Joseph Schildkraut published a review article stating that several researchers had found an association between depression and deficiency of the catecholamine family of monoamine neurotransmitters, which they had begun calling the "catecholamine hypothesis", [10] also known as the monoamine hypothesis. [11]
By 1985, the monoamine hypothesis was mostly dismissed until it was revived with the introduction of SSRIs through the successful direct-to-consumer advertising, often revolving around the claim that SSRIs correct a chemical imbalance caused by a lack of serotonin within the brain.
Serotonin levels in the human brain is measured indirectly by sampling cerebrospinal fluid for its main metabolite, 5-hydroxyindole-acetic acid, or by measuring the serotonin precursor, tryptophan. In one placebo controlled study funded by the National Institute of Health, tryptophan depletion was achieved, but they did not observe the anticipated depressive response. [12] Similar studies aimed at increasing serotonin levels did not relieve symptoms of depression. At this time, decreased serotonin levels in the brain and symptoms of depression have not been linked [13]
Although there is evidence that antidepressants inhibit the reuptake of serotonin, [14] norepinephrine, and to a lesser extent dopamine, the significance of this phenomenon in the amelioration of psychiatric symptoms is not known. Given the low overall response rates of antidepressants, [15] and the poorly understood causes of depression, it is premature to assume a putative mechanism of action of antidepressants.
While MAOIs, TCAs and SSRIs increase serotonin levels, others prevent serotonin from binding to 5-HT2Areceptors, suggesting it is too simplistic to say serotonin is a "happy neurotransmitter". In fact, when the former antidepressants build up in the bloodstream and the serotonin level is increased, it is common for the patient to feel worse for the first weeks of treatment. One explanation of this is that 5-HT2A receptors evolved as a saturation signal (people who use 5-HT2A antagonists often gain weight), telling the animal to stop searching for food, a mate, etc., and to start looking for predators. In a threatening situation it is beneficial for the animal not to feel hungry even if it needs to eat. Stimulation of 5-HT2A receptors will achieve that. But if the threat is long lasting the animal needs to start eating and mating again - the fact that it survived shows that the threat was not so dangerous as the animal felt. So the number of 5-HT2A receptors decreases through a process known as downregulation and the animal goes back to its normal behavior. This suggests that there are two ways to relieve anxiety in humans with serotonergic drugs: by blocking stimulation of 5-HT2A receptors or by overstimulating them until they decrease via tolerance.[ medical citation needed ]
One manifestation of depression is an altered hypothalamic-pituitary-adrenal axis (HPA axis) that resembles the neuro-endocrine (cortisol) response to stress, that of increased cortisol production and a subsequent impaired negative feedback mechanism. It is not known whether this HPA axis dysregulation is reactive or causative for depression. A 2003 briefing suggests that the mode of action of antidepressants may be in regulating HPA axis function. [16]
A 2011 study combines aspects of the HPA axis theory and the neurogenic theory (see below). The researchers showed that mice under unpredictable chronic mild stress (a well-known animal model of depression) have impaired hippocampal neurogenesis and greatly reduced ability of the hippocampus to regulate the HPA axis, causing ahedonia as measured by the Cookie Test. Administration of fluoxetine (an SSRI) without removing the stressor causes increased hippocampal neurogenesis, normalization of the HPA axis, and improvement of ahedonia. If X-ray irradiation is used on the hippocampus before drug treatment to prevent neurogenesis, no improvement of ahedonia occurs. However, if an irradiated mouse is given a corticotropin-releasing factor 1 antagonist – a drug that directly targets the HPA axis – ahedonia is improved. Combined with the fact that irridiation without stressing does not impair hippocampal control of the HPA axis, the authors conclude that fluoxetine works by improving hippocampal neurogenesis, which then helps restore the HPA axis, in turn leading to improvements in depression symptoms such as ahedonia. [17]
The neurogenic hypothesis states that molecular and cellular mechanisms underlying the regulation of adult neurogenesis is required for remission from depression and that neurogenesis is mediated by the action of antidepressants. [18] A broader view is that antidepressants help by increasing neuroplasticity in general. [19]
Chronic use of SSRI antidepressant increased neurogenesis in the hippocampus of rats and mice. [20] [21] [22] Other antidepressant treatments also appear associated with hippocampal neurogenesis and/or neuroplasticity: electroconvulsive therapy, which is known to be highly effective for depression, is associated with higher BDNF expression in the hippocampus [23] as well as global rewiring; [24] lithium and valporate, two mood stabilizers occasionally used as add-on treatment, are associated with increased survival and proliferation of neurons. [23] Ketamine (see also esketamine), a new fast-acting antidepressant, can increase the number of dendritic spines and restore aspects of functional connectivity after a single infusion. [25]
Other animal research suggests that long term drug-induced antidepressants effects modulate the expression of genes mediated by clock genes, possibly by regulating the expression of a second set of genes (i.e. clock-controlled genes). [26]
The delayed onset of clinical effects from antidepressants indicates involvement of adaptive changes in antidepressant effects. Rodent studies have consistently shown upregulation of the 3, 5-cyclic adenosine monophosphate (cAMP) system induced by different types of chronic but not acute antidepressant treatment, including serotonin and norepinephrine uptake inhibitors, monoamine oxidase inhibitors, tricyclic antidepressants, lithium and electroconvulsions. cAMP is synthesized from adenosine 5-triphosphate (ATP) by adenylyl cyclase and metabolized by cyclic nucleotide phosphodiesterases (PDEs). [27]
Studies on human patients have used imaging approaches to measure the changes in density and volume of specific brain areas. The grey matter volume of parts of the brain are differently increased or decreased by SSRI use. [28] It appears possible to use brain imaging to predict which patients are likely to respond to SSRI antidepressants. [29]
This section may be too technical for most readers to understand.(November 2013) |
Recent studies show pro-inflammatory cytokine processes take place during clinical depression, mania and bipolar disorder, and it is possible that symptoms of these conditions are attenuated by the pharmacological effect of antidepressants on the immune system. [30] [31] [32] [33] [34]
Studies also show that the chronic secretion of stress hormones as a result of disease, including somatic infections or autoimmune syndromes, may reduce the effect of neurotransmitters or other receptors in the brain by cell-mediated pro-inflammatory pathways, thereby leading to the dysregulation of neurohormones. [33] SSRIs, SNRIs and tricyclic antidepressants acting on serotonin, norepinephrine and dopamine receptors have been shown to be immunomodulatory and anti-inflammatory against pro-inflammatory cytokine processes, specifically on the regulation of interferon-gamma (IFN-gamma) and interleukin-10 (IL-10), as well as TNF-alpha and interleukin-6 (IL-6). Antidepressants have also been shown to suppress TH1 upregulation. [35] [36] [37] [38] [39]
Antidepressants, specifically TCAs and SNRIs (or SSRI-NRI combinations), have also shown analgesic properties. [40] [41]
These studies warrant investigation for antidepressants for use in both psychiatric and non-psychiatric illness and that a psycho-neuroimmunological approach may be required for optimal pharmacotherapy. [42] Future antidepressants may be made to specifically target the immune system by either blocking the actions of pro-inflammatory cytokines or increasing the production of anti-inflammatory cytokines. [43]
A variety of monoaminergic antidepressants have been compared below: [1] [44] [45] [46] [47] [48]
Compound | SERT | NET | DAT | H1 | mACh | α1 | α2 | 5-HT1A | 5-HT2A | 5-HT2C | D2 | MT1A | MT1B |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Agomelatine | ? | ? | ? | ? | ? | ? | ? | ? | ? | 631 | ? | 0.1 | 0.12 |
Amitriptyline | 3.13 | 22.4 | 5380 | 1.1 | 18 | 24 | 690 | 450 | 4.3 | 6.15 | 1460 | ? | ? |
Amoxapine | 58 | 16 | 4310 | 25 | 1000 | 50 | 2600 | ? | 0.5 | 2 | 20.8 | ? | ? |
Atomoxetine | 43 | 3.5 | 1270 | 5500 | 2060 | 3800 | 8800 | 10900 | 1000 | 940 | >35000 | ? | ? |
Bupropion | 9100 | 52600 | 526 | 6700 | 40000 | 4550 | >35000 | >35000 | >10000 | >35000 | >35000 | ? | ? |
Buspirone | ? | ? | ? | ? | ? | 138 | ? | 5.7 | 138 | 174 | 362 | ? | ? |
Butriptyline | 1360 | 5100 | 3940 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Citalopram | 1.38 | 5100 | 28000 | 380 | 1800 | 1550 | >10000 | >10000 | >10000 | 617 | ? | ? | ? |
Clomipramine | 0.14 | 45.9 | 2605 | 31.2 | 37 | 39 | 525 | >10000 | 35.5 | 64.6 | 119.8 | ? | ? |
Desipramine | 17.6 | 0.83 | 3190 | 110 | 196 | 100 | 5500 | >10000 | 113.5 | 496 | 1561 | ? | ? |
Dosulepin | 8.6 | 46 | 5310 | 4 | 26 | 419 | 12 | 4004 | 152 | ? | ? | ? | ? |
Doxepin | 68 | 29.5 | 12100 | 0.24 | 83.3 | 23.5 | 1270 | 276 | 26 | 8.8 | 360 | ? | ? |
Duloxetine | 0.8 | 5.9 | 278 | 2300 | 3000 | 8300 | 8600 | 5000 | 504 | 916 | >10000 | ? | ? |
Escitalopram | 0.8-1.1 | 7800 | 27400 | 2000 | 1240 | 3900 | >1000 | >1000 | >1000 | 2500 | >1000 | ? | ? |
Etoperidone | 890 | 20000 | 52000 | 3100 | >35000 | 38 | 570 | 85 | 36 | 36 | 2300 | ? | ? |
Femoxetine | 11 | 760 | 2050 | 4200 | 184 | 650 | 1970 | 2285 | 130 | 1905 | 590 | ? | ? |
Fluoxetine | 1.0 | 660 | 4176 | 6250 | 2000 | 5900 | 13900 | 32400 | 197 | 255 | 12000 | ? | ? |
Fluvoxamine | 1.95 | 1892 | >10000 | >10000 | 240000 | 1288 | 1900 | >10000 | >10000 | 6700 | >10000 | ? | ? |
Imipramine | 1.4 | 37 | 8300 | 37 | 46 | 32 | 3100 | >10000 | 119 | 120 | 726 | ? | ? |
Lofepramine | 70 | 5.4 | 18000 | 360 | 67 | 100 | 2700 | 4600 | 200 | ? | 2000 | ? | ? |
Maprotiline | 5800 | 11.1 | 1000 | 1.7 | 560 | 91 | 9400 | ? | 51 | 122 | 665 | ? | ? |
Mazindol | 100 | 1.2 | 19.7 | 600 | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Mianserin | 4000 | 71 | 9400 | 1.0 | 500 | 74 | 31.5 | 1495 | 3.21 | 2.59 | 2052 | ? | ? |
Milnacipran | 94.1 | 111 | >10000 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Mirtazapine | >10000 | 4600 | >10000 | 0.14 | 794 | 608 | 20 | 18 | 69 | 39 | 5454 | ? | ? |
Nefazodone | 400 | 490 | 360 | 24000 | 11000 | 48 | 640 | 80 | 8.6 | 72 | 910 | ? | ? |
Nisoxetine | 610 | 5.1 | 382 | ? | 5000 | ? | ? | ? | 620 | ? | ? | ? | ? |
Nomifensine | 2941 | 22.3 | 41.1 | 2700 | >10000 | 1200 | 6744 | 1183 | 937 | >10000 | >10000 | ? | ? |
Nortriptyline | 16.5 | 4.37 | 3100 | 15.1 | 37 | 55 | 2030 | 294 | 5 | 8.5 | 2570 | ? | ? |
Oxaprotiline | 3900 | 4.9 | 4340 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Paroxetine | 0.08 | 56.7 | 574 | 22000 | 108 | 4600 | >10000 | >35000 | >10000 | 19000 | 32000 | ? | ? |
Protriptyline | 19.6 | 1.41 | 2100 | 60 | 25 | 130 | 6600 | ? | 26 | ? | ? | ? | ? |
Quetiapine | >10,000 | >10,000 | >10,000 | 7 | ? | 22 | 3,630 | 376 | 99 | 2502 | 245 | ? | ? |
Reboxetine | 274 | 13.4 | 11500 | 312 | 6700 | 11900 | >10000 | >10000 | >10000 | 457 | >10000 | ? | ? |
Sertraline | 0.21 | 667 | 25.5 | 24000 | 625 | 370 | 4100 | >35000 | 1000 | 1000 | 10700 | ? | ? |
Trazodone | 367 | >10000 | >10000 | 220 | >35000 | 42 | 320 | 118 | 35.8 | 224 | 4142 | ? | ? |
Trimipramine | 149 | 2450 | 3780 | 1.4 | 58 | 24 | 680 | ? | ? | ? | ? | ? | ? |
Venlafaxine | 7.7 | 2753 | 8474 | >35000 | >35000 | >35000 | >35000 | >35000 | >35000 | >10000 | >35000 | ? | ? |
Vilazodone | 0.1 | ? | ? | ? | ? | ? | ? | 2.3 | ? | ? | ? | ? | ? |
Viloxazine | 17300 | 155 | >100000 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Vortioxetine | 1.6 | 113 | >1000 | ? | ? | ? | ? | 15 (Agonist) | ? | 180 | ? | ? | ? |
Zimelidine | 152 | 9400 | 11700 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
The values above are expressed as equilibrium dissociation constants in nanomoles/liter. A smaller dissociation constant indicates more affinity. SERT, NET, and DAT correspond to the abilities of the compounds to inhibit the reuptake of serotonin, norepinephrine, and dopamine, respectively. The other values correspond to their affinity for various receptors.
Drug | Bioavailability | t1/2 (hr) for parent drug (active metabolite) | Vd (L/kg unless otherwise specified) | Cp (ng/mL) parent drug (active metabolite) | Tmax | Protein binding Parent drug (active metabolite(s)) | Excretion | Enzymes responsible for metabolism | Enzymes inhibited [53] |
---|---|---|---|---|---|---|---|---|---|
Tricyclic antidepressant (TCAs) | |||||||||
Amitriptyline | 30–60% | 9–27 (26–30) | ? | 100–250 | 4 hr | >90% (93–95%) | Urine (18%) | ? | |
Amoxapine | ? | 8 (30) | 0.9–1.2 | 200–500 | 90 mins | 90% | Urine (60%), faeces (18%) | ? | ? |
Clomipramine | 50% | 32 (70) | 17 | 100–250 (230–550) | 2–6 hr | 97–98% | Urine (60%), faeces (32%) | CYP2D6 | ? |
Desipramine | ? | 30 | ? | 125–300 | 4–6 hr | ? | Urine (70%) | CYP2D6 | ? |
Doxepin | ? | 18 (30) | 11930 | 150–250 | 2 hr | 80% | Urine | ? | |
Imipramine | High | 12 (30) | 18 | 175–300 | 1–2 hr | 90% | Urine | ? | |
Lofepramine | 7% | 1.7–2.5 (12–24) | ? | 30–50 (100–150) | 1 hr | 99% (92%) | Urine | CYP450 | ? |
Maprotiline | High | 48 | ? | 200–400 | 8–24 hr | 88% | Urine (70%); faeces (30%) | ? | ? |
Nortriptyline | ? | 28–31 | 21 | 50–150 | 7–8.5 hr | 93–95% | Urine, faeces | CYP2D6 | ? |
Protriptyline | High | 80 | ? | 100–150 | 24–30 hr | 92% | Urine | ? | ? |
Tianeptine | 99% | 2.5–3 | 0.5–1 | ? | 1–2 hr | 95–96% | Urine (65%) | ? | ? |
Trimipramine | 41% | 23–24 (30) | 17–48 | 100–300 | 2 hr | 94.9% | Urine | ? | ? |
Monoamine oxidase inhibitors (MAOIs) | |||||||||
Moclobemide | 55–95% | 2 | ? | ? | 1–2 hr | 50% | Urine, faeces (<5%) | ? | MAOA |
Phenelzine | ? | 11.6 | ? | ? | 43 mins | ? | Urine | MAOA | MAO |
Tranylcypromine | ? | 1.5–3 | 3.09 | ? | 1.5–2 hr | ? | Urine | MAO | MAO |
Selective serotonin reuptake inhibitors (SSRIs) | |||||||||
Citalopram | 80% | 35–36 | 12 | 75–150 | 2–4 hr | 80% | Urine (15%) | CYP1A2 (weak) | |
Escitalopram | 80% | 27–32 | 20 | 40–80 | 3.5–6.5 hr | 56% | Urine (8%) | CYP2D6 (weak) | |
Fluoxetine | 72% | 24–72 (single doses), 96–144 (repeated dosing) | 12–43 | 100–500 | 6–8 hr | 95% | Urine (15%) | CYP2D6 | |
Fluvoxamine | 53% | 18 | 25 | 100–200 | 3–8 hr | 80% | Urine (85%) | ||
Paroxetine | ? | 17 | 8.7 | 30–100 | 5.2–8.1 (IR); 6–10 hr (CR) | 93–95% | Urine (64%), faeces (36%) | CYP2D6 | |
Sertraline | 44% | 23–26 (66) | ? | 25–50 | 4.5–8.4 hr | 98% | Urine (12–14% unchanged), faeces (40–45%) | ||
Serotonin-norepinephrine reuptake inhibitors (SNRIs) | |||||||||
Desvenlafaxine | 80% | 11 | 3.4 | ? | 7.5 hr | 30% | Urine (69%) | CYP3A4 | CYP2D6 (weak) |
Duloxetine | High | 11–12 | 3.4 | ? | 6 hr (empty stomach), 10 hr (with food) | >90% | Urine (70%; <1% unchanged), faeces (20%) | CYP2D6 (moderate) | |
Levomilnacipran | 92% | 12 | 387–473 L | ? | 6–8 hr | 22% | Urine (76%; 58% as unchanged drug & 18% as N-desmethyl metabolite) | ? | |
Milnacipran | 85-90% | 6-8 (L-isomer), 8-10 (D-isomer) | 400 L | ? | 2–4 hr | 13% | Urine (55%) | ? | ? |
Venlafaxine | 45% | 5 (11) | 7.5 | ? | 2-3 hr (IR), 5.5–9 hr (XR) | 27–30% (30%) | Urine (87%) | CYP2D6 | CYP2D6 (weak) |
Others | |||||||||
Agomelatine | ≥80% | 1–2 hr | 35 L | ? | 1–2 hr | 95% | Urine (80%) | ? | |
Bupropion | ? | 8–24 (IR; 20, 30, 37), 21±7 (XR) | 20–47 | 75–100 | 2 hr (IR), 3 hr (XR) | 84% | Urine (87%), faeces (10%) | CYP2B6 | CYP2D6 (moderate) |
Mianserin | 20-30% | 21–61 | ? | ? | 3 hr | 95% | Faeces (14–28%), urine (4–7%) | CYP2D6 | ? |
Mirtazapine | 50% | 20–40 | 4.5 | ? | 2 hr | 85% | Urine (75%), faeces (15%) | ? | |
Nefazodone | 20% (decreased by food) | 2–4 | 0.22–0.87 | ? | 1 hr | >99% | Urine (55%), faeces (20–30%) | CYP3A4 | ? |
Reboxetine | 94% | 12–13 | 26 L (R,R diastereomer), 63 L (S,S diastereomer) | ? | 2 hr | 97% | Urine (78%; 10% as unchanged) | CYP3A4 | ? |
Trazodone | ? | 6–10 | ? | 800–1600 | 1 hr (without food), 2.5 hr (with food) | 85–95% | Urine (75%), faeces (25%) | CYP2D6 | ? |
Vilazodone | 72% (with food) | 25 | ? | ? | 4–5 hr | 96–99% | Faeces (2% unchanged), urine (1% unchanged) | ? | |
Vortioxetine | ? | 66 | 2600 L | ? | 7–11 hr | 98% | Urine (59%), faeces (26%) | ? |
Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction.
The hypothalamic–pituitary–adrenal axis is a complex set of direct influences and feedback interactions among three components: the hypothalamus, the pituitary gland, and the adrenal glands. These organs and their interactions constitute the HPS axis.
Duloxetine, sold under the brand name Cymbalta among others, is a medication used to treat major depressive disorder, generalized anxiety disorder, obsessive-compulsive disorder, fibromyalgia, neuropathic pain and central sensitization. It is taken by mouth.
Serotonin–norepinephrine reuptake inhibitors (SNRIs) are a class of antidepressant medications used to treat major depressive disorder (MDD), anxiety disorders, social phobia, chronic neuropathic pain, fibromyalgia syndrome (FMS), and menopausal symptoms. Off-label uses include treatments for attention-deficit hyperactivity disorder (ADHD), and obsessive–compulsive disorder (OCD). SNRIs are monoamine reuptake inhibitors; specifically, they inhibit the reuptake of serotonin and norepinephrine. These neurotransmitters are thought to play an important role in mood regulation. SNRIs can be contrasted with the selective serotonin reuptake inhibitors (SSRIs) and norepinephrine reuptake inhibitors (NRIs), which act upon single neurotransmitters.
Azapirones are a class of drugs used as anxiolytics, antidepressants, and antipsychotics. They are commonly used as add-ons to other antidepressants, such as selective serotonin reuptake inhibitors (SSRIs).
Psychoneuroimmunology (PNI), also referred to as psychoendoneuroimmunology (PENI) or psychoneuroendocrinoimmunology (PNEI), is the study of the interaction between psychological processes and the nervous and immune systems of the human body. It is a subfield of psychosomatic medicine. PNI takes an interdisciplinary approach, incorporating psychology, neuroscience, immunology, physiology, genetics, pharmacology, molecular biology, psychiatry, behavioral medicine, infectious diseases, endocrinology, and rheumatology.
Imipramine, sold under the brand name Tofranil, among others, is a tricyclic antidepressant (TCA) mainly used in the treatment of depression. It is also effective in treating anxiety and panic disorder. Imipramine is taken by mouth.
Pindolol, sold under the brand name Visken among others, is a nonselective beta blocker which is used in the treatment of hypertension. It is also an antagonist of the serotonin 5-HT1A receptor, preferentially blocking inhibitory 5-HT1A autoreceptors, and has been researched as an add-on therapy to various antidepressants, such as clomipramine and the selective serotonin reuptake inhibitors (SSRIs), in the treatment of depression and obsessive-compulsive disorder.
Biological psychiatry or biopsychiatry is an approach to psychiatry that aims to understand mental disorder in terms of the biological function of the nervous system. It is interdisciplinary in its approach and draws on sciences such as neuroscience, psychopharmacology, biochemistry, genetics, epigenetics and physiology to investigate the biological bases of behavior and psychopathology. Biopsychiatry is the branch of medicine which deals with the study of the biological function of the nervous system in mental disorders.
Post-stroke depression (PSD) is a form of depression that may occur after a stroke. PSD significantly impacts stroke recovery and the overall quality of life of those affected. It is particularly associated with strokes affecting the basal ganglia or the anterior regions of the brain, including the hippocampus and prefrontal cortex. Treatment can include medications such as SSRIs, SNRIs, tricyclic antidepressants, and/or cognitive behavioral therapy.
A serotonin–norepinephrine–dopamine reuptake inhibitor (SNDRI), also known as a triple reuptake inhibitor (TRI), is a type of drug that acts as a combined reuptake inhibitor of the monoamine neurotransmitters serotonin, norepinephrine, and dopamine. It does this by concomitantly inhibiting the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT), respectively. Inhibition of the reuptake of these neurotransmitters increases their extracellular concentrations and, therefore, results in an increase in serotonergic, adrenergic, and dopaminergic neurotransmission. The naturally-occurring and potent SNDRI cocaine is widely used recreationally and often illegally for the euphoric effects it produces.
N-Acetylserotonin (NAS), also known as normelatonin, is a naturally occurring chemical intermediate in the endogenous production of melatonin from serotonin. It also has biological activity in its own right, including acting as a melatonin receptor agonist, an agonist of the TrkB, and having antioxidant effects.
The 5-HT2C receptor is a subtype of the 5-HT2 receptor that binds the endogenous neurotransmitter serotonin (5-hydroxytryptamine, 5-HT). Like all 5-HT2 receptors, it is a G protein-coupled receptor (GPCR) that is coupled to Gq/G11 and mediates excitatory neurotransmission. HTR2C denotes the human gene encoding for the receptor, that in humans is located on the X chromosome. As males have one copy of the gene and females have one of the two copies of the gene repressed, polymorphisms at this receptor can affect the two sexes to differing extent.
The serotonin 1A receptor is a subtype of serotonin receptors, or 5-HT receptors, that binds serotonin, also known as 5-HT, a neurotransmitter. 5-HT1A is expressed in the brain, spleen, and neonatal kidney. It is a G protein-coupled receptor (GPCR), coupled to the Gi protein, and its activation in the brain mediates hyperpolarization and reduction of firing rate of the postsynaptic neuron. In humans, the serotonin 1A receptor is encoded by the HTR1A gene.
The biology of depression is the attempt to identify a biochemical origin of depression, as opposed to theories that emphasize psychological or situational causes.
Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions.
A monoamine reuptake inhibitor (MRI) is a drug that acts as a reuptake inhibitor of one or more of the three major monoamine neurotransmitters serotonin, norepinephrine, and dopamine by blocking the action of one or more of the respective monoamine transporters (MATs), which include the serotonin transporter (SERT), norepinephrine transporter (NET), and dopamine transporter (DAT). This in turn results in an increase in the synaptic concentrations of one or more of these neurotransmitters and therefore an increase in monoaminergic neurotransmission.
Epigenetics of depression is the study of how epigenetics contribute to depression.
Immuno-psychiatry, according to Pariante, is a discipline that studies the connection between the brain and the immune system. It differs from psychoneuroimmunology by postulating that behaviors and emotions are governed by peripheral immune mechanisms. Depression, for instance, is seen as malfunctioning of the immune system.
Adult neurogenesis is the process by which functional, mature neurons are produced from neural stem cells (NSCs) in the adult brain. In most mammals, including humans, it only occurs in the subgranular zone of the hippocampus, and in the olfactory bulb. The neurogenesis hypothesis of depression proposes that major depressive disorder is caused, at least partly, by impaired neurogenesis in the subgranular zone of the hippocampus.
{{cite book}}
: |work=
ignored (help)