Endocrine Functions of Brain Dopamine
Nira Ben-Jonathan in Dopamine, 2020
The pineal gland is a small structure located on the epithalamus. Its main secretory product is melatonin, which is synthesized from tryptophan by four enzymatic steps in the indoleamine biosynthetic pathway (Figure 4.2). Dietary tryptophan is absorbed into the bloodstream from the gut and is circulated through the body. In cells that express tryptophan hydroxylase (TPOH), tryptophan is hydroxylated to 5-hydroxy-tryptophan in the mitochondria, followed by decarboxylation by aromatic amino acid decarboxylase (AADC; the same enzyme that converts L-Dopa to DA) to serotonin (5-hydroxy-tryptamine or 5-HT). Serotonin is the final product of the indoleamine pathway in many brain and peripheral locations, where it functions as a neurotransmitter and/or a hormone. In the pineal gland, however, serotonin is further acetylated on its free amine by serotonin N-acetyl transferase (AANAT), followed by O-methylation on the hydroxyl group by acetyl-serotonin-O-methyl transferase (ASMT), generating melatonin. Among the four biosynthetic enzymes in the pineal, the activities of TPOH and AANAT increase at night, while those of AADC and HIOMT run continuously.
Neuroendocrine Regulation of Hematopoiesis
Herman Friedman, Thomas W. Klein, Andrea L. Friedman in Psychoneuroimmunology, Stress, and Infection, 2020
Melatonin is an indoleamine synthesized from serotonin. Its synthesis and release which occur primarily in the pineal gland follows a circadian rhythm with the highest blood concentration occurring at night in all species.19 In previous work we have shown that melatonin can correct immunodeficiency states which may follow acute stress, viral diseases, aging or drug treatment9 We also observed that melatonin was able to antagonize the effect of high dose cyclophosphamide on antibody production.20 This finding has been then confirmed and extended by other authors.21,22 Such interesting effects of melatonin seem to depend on activated CD4+, T-cells which upon melatonin stimulation show an enhanced synthesis and/or release of opioid peptides, IL-2 and γ-interferon.9,22–24 On the basis of our animal studies,9 we have investigated the clinical effect of melatonin in association with low-dose interleukin-2 in cancer patients and found that this association represents a well tolerated strategy capable of determining an apparent control of tumor growth in patients with advanced solid neoplasms.25–28
Testosterone signaling in spermatogenesis, male fertility and infertility
Rajender Singh in Molecular Signaling in Spermatogenesis and Male Infertility, 2019
Melatonin is an indoleamine, which is a major secretory product of the pineal gland. It regulates the circadian cycle and acts as a cytokine, neuromodulator and biological response modifier. This hormone functions as a regulator of the reproductive physiology in response to environmental light in seasonally dependent mammals. It displays both hydrophilic and lipophilic properties and can enter testicular cells by crossing the blood-testis barrier. Multiple studies have demonstrated the localization of melatonin receptors on the reproductive system with primary target sites on the testis, epididymis, vas deferens, prostate and ovary. Melatonin is also suggested to regulate the timing for the release of hormones in the female reproductive system. It can act through several receptors such as melatonin receptor 1 (MT1), melatonin receptor 2 (MT2) and retinoid acid receptor–related orphan receptor A (RORα) (28). MT1 and MT2 interact with G-protein to regulate testosterone synthesis by modulating cAMP signal transduction (29). Research suggests that RORα directly activates the aromatase to accelerate the conversion of androgens into estrogens (30).
Educational Materials and Image Induction Increase Treatment Credibility
Published in Journal of Psychoactive Drugs, 2022
Recent investigations of psilocybin-assisted therapy (PAT) suggest that the plant-derived indoleamine might hold promise in the treatment of depression. Symptom reduction with moderate to large effect sizes have been detected following psilocybin administration in conjunction with supportive psychotherapy (Carhart-Harris et al. 2016; Davis et al. 2021; Griffiths et al. 2016; Ross et al. 2016). Follow-ups show enduring benefits at the six- to twelve-month mark, and an absence of lasting adverse effects (Carhart-Harris et al. 2018; Griffiths et al. 2016; Gukasyan et al. 2022; Ross et al. 2016). A comparison of PAT and the antidepressant escitalopram found comparable changes in patient improvement (Carhart-Harris et al. 2021). Furthermore, the low toxicity ratio of psilocybin and lack of dependence effects (Gable 2004; Rucker et al. 2016) makes PAT a potentially viable alternative to existing treatments for depressed individuals. The precise mechanism by which the molecule facilitates positive changes is still under investigation. Working theories relate to the occurrence of mystical experiences (McCulloch et al. 2022; Roseman, Nutt, and Carhart-Harris 2018) and emotional breakthrough experiences (Close et al. 2020; Roseman et al. 2019). However, controversy about the interpretation of available data likely contribute to ambivalent perceptions of PAT (Doss, Barrett, and Corlett 2022; Earleywine and Herrmann 2022).
Effects of a Pedometer-Based Walking Home Program Plus Resistance Training on Inflammatory Cytokines and Depression in Thai Older People with Sarcopenia: A Three-Arm Randomized Controlled Trial
Published in Clinical Gerontologist, 2022
Kornanong Yuenyongchaiwat, Chareeporn Akekawatchai, Janya Khattiya
Furthermore, inflammatory cytokines are associated with the symptoms of depression. Pro-inflammatory profiles, such as high c-reactive protein (CRP) and IL-12, is linked to an elevation in depression (Osimo et al., 2020). One meta-analysis found a significant elevation in immune marker levels such as IL-6, TNF α, and CRP in patients with depression compared with healthy participants (Osimo et al., 2020). The pathogenesis of depression activates the hypothalamo-pituitary-adrenocortical (HPA) axis, and triggers neuronal serotonin transporters and the stimulation of the indoleamine 2,3-dioxygenase, resulting in tryptophan depletion, Consequently, the associated psychological changes may activate depressive symptoms (Berthold-Losleben & Himmerich, 2008; Smith et al., 1997). Therefore, these inflammatory profiles may be associated with depression and the markers of sarcopenia, such as physical performance, muscle mass, or muscle strength.
The Volumetric Changes of the Pineal Gland with Age: An Atlas-based Structural Analysis
Published in Experimental Aging Research, 2022
Minoo Sisakhti, Lida Shafaghi, Seyed Amir Hossein Batouli
The pineal gland is an interhemispheric neuroendocrine organ that, as a small canonical gland of about 100 mm3, along with habenula nuclei is located medially in the epithalamus of the vertebrate brain, and is surrounded by the structures such as the posterior third ventricle, thalami, and the splenium of the corpus callosum. It contains varied categories of cells such as pinealocytes (80% of the gland), astrocytes, microglia, and more recently evidenced pineal neurons and peptidergic neuron-like cells. This circumventricular organ, as a whole apparatus, concludes mechanisms for synthesis and secretion (into the bloodstream and CSF) of the indoleamine melatonin (N-acetyl-methoxytryptamine)-as the most identified one-, as well as the serotonin, arginine, vasotocin, and some forms of the neurosteroids (Beker-Acay et al., 2016; Khavinson & Lin’kova, 2012; J. Park et al., 2018; Sigurdardottir et al., 2016).
Related Knowledge Centers
- Biochemistry
- Melatonin
- Molecular Geometry
- Monoamine Neurotransmitter
- Sleep
- Catecholamine
- Neurotransmitter
- Serotonin
- Ethylamine
- Mood