Ramelteon Research Articles

PTZ KINDLING MODEL: EVALUATION OF EEG FACTOR AND BIOCHEMISTRY PARAMETERS UNDER THE INFLUENCE OF RAMELTEON

Many selective synthetic melatonin receptor agonists have anticonvulsant/anti-epileptogenic properties. These agonists bind to melatonin receptor 1 (MT1) and receptor 2 (MT2), causing their activation. Therefore, we evaluated the anticonvulsant effect of Ramelteon (RMLT) as a melatonin agonist in the PTZ (Pentylenetetrazol)-kindling model. In the study, 36 male Wistar Albino rats were assessed in 6 groups (Sham, PTZ, dimethylsulphoxide (DMSO), Valproic acid (VPA) (150 mg/kg) + PTZ, RMLT (30 mg/kg)+PTZ, VPA+RMLT+PTZ). Cortical electroencephalography (EEG) data were recorded for all groups. Seizures were scored according to the Racine scale. Seizure scores and onset times of the first myoclonic movements were compared in EEG traces. Total antioxidant status (TAS), total oxidant status (TOS), catalase, myeloperoxidase (MPO), and Thiol levels were measured in serum samples. Also, Calcineurin (CaN), Neuropeptide-Y (NPY), Neuron Specific Enolase (NSE), and S100B levels were measured in brain tissue samples. There was a significant difference between the PTZ and PTZ+Valproic acid+RMLT groups for the onset of the first myoclonic movements and the rate of spikes in the EEG traces in Racine's convulsion stages (P 0.05). RMLT has anticonvulsant properties. Additionally, the receptor preference of RMLT can be investigated.

An unidentified yet notable modification on I Na and I K (DR) caused by ramelteon.

Despite advancement in anti-seizure medications, 30% of patients continue to experience recurrent seizures. Previous data indicated the antiepileptic properties of melatonin and its agonists in several animal models. However, the underlying mechanisms of melatonin and its agonists on cellular excitability remain poorly understood. In this study, we demonstrated the electrophysiological changes of two main kinds of ion channels that are responsible for hyperexcitability of neurons after introduction of melatonin agonists- ramelteon (RAM). In Neuro-2a cells, the amplitude of voltage-gated Na+ (I Na) and delayed-rectifier K+ currents (I K (DR)) could be suppressed under RAM. The IC50 values of 8.7 and 2.9 μM, respectively. RAM also diminished the magnitude of window Na+ current (I Na (W)) elicited by short ascending ramp voltage, with unchanged the overall steady-state current-voltage relationship. The decaying time course of I Na during a train of depolarizing pulses arose upon the exposure to RAM. The conditioning train protocol which blocked I Na fitted the recovery time course into two exponential processes and increased the fast and slow time constant of recovery the presence of RAM. In pituitary tumor (GH3) cells, I Na amplitude was also effectively suppressed by the RAM. In addition, GH3-cells exposure to RAM decreased the firing frequency of spontaneous action potentials observed under current-clamp conditions. As a result, the RAM-mediated effect on INa was closely associated with its ability to decrease spontaneous action potentials. Collectively, we found the direct attenuation of I Na and I K (DR) caused by RAM besides the agonistic action on melatonin receptors, which could partially explain its anti-seizure activity.

Protective efficacy of ramelteon on methotrexate-induced DNA damage

Ramelteon (RMLT) is a melatonin receptor agonist that it has antioxidative and anti-inflammatory effects associated with DNA damage through different mechanisms of action. In this regard, we investigated the potential usefulness of RMLT as a protective agent against methotrexate (MTX)-induced DNA damage. Four groups were constituted from 32 Wistar albino rats: Negative control, RMLT, MTX, and MTX + RMLT. Twenty mg/kg MTX (i.p., single dose) and RMLT 10 mg/kg (oral, 7 days) was administered. Comet assay was used and the parameter %TailDNA was used to detect DNA damage. %TailDNA was 4.90 ± 0.19 in the control group, 7.85 ± 0.33 in the MTX group, 5.49 ± 0.24 in the RMLT group, and 5.86 ± 0.23 in the MTX + RMLT group. While there was a significant increase in DNA damage in the MTX-treated group compared to the control group, there was a significant reduction in DNA damage in the MTX + RMLT group, compared to the MTX group (p < 0.001). In conclusion, it was observed that combined treatment with RMLT significantly reduced MTX-induced DNA damage.

Quantum mechanics insights into melatonin and analogs binding to melatonin MT1 and MT2 receptors

Melatonin receptors MT1 and MT2 are G protein-coupled receptors that mediate the effects of melatonin, a hormone involved in circadian rhythms and other physiological functions. Understanding the molecular interactions between these receptors and their ligands is crucial for developing novel therapeutic agents. In this study, we used molecular docking, molecular dynamics simulations, and quantum mechanics calculation to investigate the binding modes and affinities of three ligands: melatonin (MLT), ramelteon (RMT), and 2-phenylmelatonin (2-PMT) with both receptors. Based on the results, we identified key amino acids that contributed to the receptor-ligand interactions, such as Gln181/194, Phe179/192, and Asn162/175, which are conserved in both receptors. Additionally, we described new meaningful interactions with Gly108/Gly121, Val111/Val124, and Val191/Val204. Our results provide insights into receptor-ligand recognition’s structural and energetic determinants and suggest potential strategies for designing more optimized molecules. This study enhances our understanding of receptor-ligand interactions and offers implications for future drug development.

The roles of angiotensin-converting enzyme 2 inhibitor, melatonin and its agonist on angiotensin II reactivity in intact and denuded rat aortic rings

Background The pineal product melatonin (MEL) modulates blood vessels through G protein-coupled receptors (GPCRs) called melatonin type 1 receptor (MT1R) and melatonin type 2 receptor (MT2R), in that order. The renin-angiotensin system (RAS), which breaks down angiotensin II (Ang II) to create Ang 1–7, is thought to be mostly controlled by angiotensin-converting enzyme-2 (ACE2). Aim The current work examines the involvement of ACE2 inhibitor, MEL, and ramelteon (RAM) in the vascular response to Ang II activities in the endothelial denuded (E-) and intact (E+) rat isolated thoracic aortic rings. Method The isometric tension was measured to evaluate the vascular Ang II contractility using dose response curve (DRC). Results MEL and RAM caused a rightward shift of Ang II in endothelium E + and endothelium E- aorta. Conclusion According to the current study, the distribution of MEL receptors and the endothelium’s condition are related to the vasomodulatory effect of MEL and ACE2 on Ang II attenuation. These physiological interactions can control vascular tone and increase Ang II reactivity denude endothelial layaer.

Does ramelteon have an ameliorative effect in MTX-induced testicular injury?

Aims: The aim of this study was to investigate the potential protective effect of Ramelteon (RMT), which exhibits antioxidant, anti-inflammatory and antiapoptotic properties, against testicular damage induced by Methotrexate (MTX), which is widely used in the treatment of various diseases, including chemotherapy.&#x0D; Methods: 32 Wistar albino rats were equally divided into four groups: Control (group I), MTX (group II), MTX+RMT (group III) and RMT (group IV). Histologic evaluation was performed using Hematoxylin and Eosin (H&amp;E) staining, immunohistochemical analysis using TNF-alpha and Cas-3, and biochemical evaluation using TAS, TOS and OSI.&#x0D; Results: Histologic analysis using H&amp;E staining revealed a significant difference between group I and groups II and III (p0.05). While normal histologic structures were observed in groups I and IV, histopathologic findings were noted in groups II and III. Immunohistochemical evaluation of TNF-alpha and Cas-3 showed a significant difference between group I and groups II and III (p0.05). The highest immunostaining intensity was observed in group II. Biochemical evaluation revealed statistically significant differences in TAS, TOS and OSI parameters reflecting oxidative stress differences between the groups (p

EVALUATION OF THE PROTECTIVE EFFECT OF RAMELTEON IN METHOTREXATE INDUCED NEPHROTOXICITY

Objective&#x0D; Methotrexate (MTX), which is used as an&#x0D; immunosuppressive and anticancer drug, causes&#x0D; serious toxic side effects in many organs, including&#x0D; the kidney. Activation of apoptotic pathways through&#x0D; oxidative stress is involved in the mechanism of MTX&#x0D; mediated nephrotoxicity. In our study, we investigated&#x0D; the protective effects of ramelteon (RML), an analogue&#x0D; of melatonin, whose antioxidant and antiapoptotic&#x0D; properties are well known, on MTX nephrotoxicity.&#x0D; Material and Method&#x0D; 32 rats were divided into 4 groups as Control, MTX,&#x0D; MTX+RML and RML. According to the groups, saline&#x0D; or RML (10 mg/kg) was administered by oral gavage for&#x0D; 7 days, and on the 2nd day, 20 mg of MTX or the same&#x0D; volume of saline was administered intraperitoneally&#x0D; according to the groups. At the end of the experiment,&#x0D; the rats were sacrificed and kidney tissues were&#x0D; examined histopathologically with Hematoxylin-Eosin&#x0D; (HE) staining and immunohistochemically (IHC) with&#x0D; caspase-3 and TNF-α staining. In addition, serum BUN,&#x0D; creatinine levels were measured, kidney Total Oxidant&#x0D; and Antioxidant Status (TAS, TOS) levels were studied&#x0D; and Oxidative Stress Index (OSI) was calculated.&#x0D; Results&#x0D; Creatinine, TOS and OSI levels in the MTX group&#x0D; were found to be significantly higher than in the control&#x0D; group. In HE staining, tissue damage was significantly&#x0D; higher in MTX group compared to the control group,&#x0D; and cas-3 and TNF-α staining levels were increased in&#x0D; IHC staining. These findings were found to be reversed&#x0D; in the MTX+RML group.&#x0D; Conclusion&#x0D; We show that RML treatment improves the findings of&#x0D; MTX-induced nephrotoxicity. RML may be a promising&#x0D; drug in MTX nephrotoxicity.

Modulatory effect of n-3 polyunsaturated fatty acids on depressive-like behaviors in rats with chronic sleep deprivation: potential involvement of melatonin receptor pathway and brain lipidome.

Clinical evidence suggests that a bidirectional relationship is present between sleep loss and psychiatric disorders. Both melatonin receptor agonist ramelteon (RMT) and n-3 polyunsaturated fatty acids (n-3 PUFAs) exhibit antidepressant effects, while their underlying molecular mechanisms might be different. Thus, the present study aims to investigate the add-on effects and possible mechanisms of how RMT and different n-3 PUFAs modulate the melatonin receptor pathway as well as brain lipidome to ameliorate the neuropsychiatric behaviors displayed in rats under chronic sleep deprivation. Thirty-one 6-week-old male Wistar rats were divided into five groups: control (C), sleep deprivation (S), sleep deprivation treated with RMT (SR), sleep deprivation treated with RMT and eicosapentaenoic acid (C20:5n-3, EPA) (SRE), and sleep deprivation treated with RMT and docosahexaenoic acid (C22:6n-3, DHA) (SRD) groups. The results reveal that RMT plus EPA alleviated depressive-like behavior when the rats were subjected to the forced swimming test, whereas RMT plus DHA alleviated anxiety-like behavior when the rats were subjected to the elevated plus maze test. The results of a western blot analysis further revealed that compared with the rats in the S group, those in the SRE and SRD groups exhibited a significantly increased expression of MT2 in the prefrontal cortex, with greater benefits observed in the SRE group. In addition, decreased BDNF and TrkB expression levels were upregulated only in the SRE group. Lipidomic analysis further revealed possible involvement of aberrant lipid metabolism and neuropsychiatric behaviors. RMT plus EPA demonstrated promise as having the effects of reversing the levels of the potential biomarkers of depressive-like behaviors. RMT plus EPA or DHA could ameliorate depressive- and anxiety-like behaviors in sleep-deprived rats through the alteration of the lipidome and MT2 receptor pathway in the brain, whereas EPA and DHA exerted a differential effect.

Protective effects of melatonin receptor agonists on endotoxin-induced uveitis in rats.

Melatonin has an important role in regulating a variety of physiological functions of the body. We investigated the protective effects of Agomelatine (AGO) and Ramelteon (RAME) on Endotoxin-Induced Uveitis (EIU) in rats. 70 rats were randomly divided into fourteen groups. Healthy group normal saline, (IP), Uveitis group (200 μg/kg lipopolysaccharide (LPS), SC), DEX group (200 μg/kg LPS plus 1 mg/kg dexamethasone, IP), AGO20 group received 200 μg/kg LPS plus 20 mg/kg AGO, AGO40 group received 200 μg/kg LPS plus 40 mg/kg AGO, RAME2 group received 200 μg/kg LPS plus 2 mg/kg RAME, and group RAME4 received 200 μg/kg LPS plus 4 mg/kg RAME. Each group had two subgroups: the 3rd and 24th hr. The eye tissues were collected and investigated biomicroscopically (clinical manifestations and scoring, molecularly(qRT-PCR analyses of tumor necrosis factor-α (TNF-α), vascular endothelial growth factor (VEGF), and caspase 3 and caspase 9 mRNA expression), biochemically (Superoxide dismutase activity (SOD), Glutathione (GSH), and malondialdehyde levels (MDA)) and histopathologically (staining with Harris Hematoxylin and Eosin Y). Melatonin receptor agonist treatment reduced the clinical score count of ocular inflammation in the uveitic rats. TNF-α, VEGF, caspase 9, and caspase 3 levels markedly decreased in the uveitic rats. Melatonin receptor agonists significantly ameliorated fixed changes in GSH, SOD, and MDA levels. Melatonin receptor agonists also ameliorated histopathological injury in eye tissues associated with uveitis. Melatonin receptor agonists ameliorated the inflammatory response in EIU. These findings suggest that melatonin receptor agonists may represent a potential novel therapeutic drug for uveitis treatment.

Ramelteon and mechanism of its restorative effect in an experimental lung disease model

Methotrexate (MTX) is an anticancer agent widely used in clinical practice for various oncological, rheumatological, autoimmune, and inflammatory diseases. However, the side effects of MTX limit its usage for treatment. In addition, diffuse alveolar damage, interstitial pneumonia, fibrosis, and pleural reactions may be encountered in MTX-induced pulmonary toxicity. Ramelteon (RML), a melatonin receptor agonist, has antioxidant, anti-inflammatory, and protective effects are shown by several studies. This study aimed to show the antioxidant, anti-inflammatory, and antiapoptotic effects of RML and its effect on the airway surface liquid volume homeostasis via aquaporins (AQP) in MTX-induced lung injury. Thirty-two female Wistar Albino rats were grouped into four groups as control, MTX (20 mg/kg, intraperitoneally, a single dose), MTX + RML, and RML (10 mg/kg, via oral gavage, for seven days) groups. Once the experiment ended, the rats’ lung tissues were taken for biochemical, genetic, histopathological, and immunohistochemical examinations. MTX significantly increased oxidative stress index and total oxidative status, and decreased total antioxidant status levels by 202.0%, 141.4%, 20.2%, respectively, relative to the control (p ˂ 0.001 for all). AQP-1/5, which is an indicator of lung damage, was also found to decrease significantly (p ˂ 0.001). In addition, a significant increase was observed in interleukin-1β, interferon-beta, and caspase-8 expressions and histopathological changes as a result of immunohistochemical and histochemical examinations (p ˂ 0.001). RML treatment ameliorated all these changes and significantly regressed lung damage. Our results suggest that RML might be used as a lung-protective agent in various models of lung and tissue injury.

Ameliorating effects of ramelteon on oxidative stress, inflammation, apoptosis, and autophagy markers in methotrexate-induced cerebral toxicity.

Objective(s):Methotrexate (MTX) is a widely used chemotherapeutic agent that, however, is known to have serious side effects such as neurotoxicity. In the present study, we aimed to evaluate the possible favorable effects of ramelteon (RMLT) on MTX-induced cerebral toxicity. Materials and Methods:Thirty-two male Wistar albino rats were divided into four groups: Control group, MTX group (20 mg/kg MTX, IP, single dose), MTX+RMLT group (20 mg/kg MTX, IP, single dose + 10 mg/kg RMLT, by gavage, 7 days), and RMLT group (10 mg/kg RMLT, by gavage, 7 days). Results: In the MTX group, increased levels of total oxidant status (TOS) and oxidative stress index (OSI) levels and decreased levels of total antioxidant status (TAS) level were observed. RMLT significantly reversed oxidative stress parameters. Real-time PCR analysis revealed that MTX increased the expressions of Beclin-1 and autophagy-related gene 12 (ATG12). These expressions were significantly decreased by RMLT. Vacuolar changes, apoptotic cells, and inflammatory cell infiltration induced by MTX were ameliorated by RMLT treatment. Increased tumor necrosis factor-α (TNF- α) and Caspase-3 activities induced by MTX were returned to their normal levels by RMLT. Conclusion:All our results demonstrate that RMLT alleviates the harmful effects of MTX on the cerebral cortex tissue. Therefore, RMLT may be considered for supportive therapy for preventing side effects of MTX in patients needing MTX therapy.

Melatonin receptor agonist ramelteon alleviates experimental acute ocular inflammation via HIF-1Α/VEGF/E-NOS signaling.

Ramelteon (RML) is a potent, selective agonist of the high-affinity melatonin receptor 1 and 2 receptors. In addition, RML is known to have antioxidant and anti-inflammatory effects. In this study, we aimed to investigate the effects of RML on HIF-1α, VEGF and e-NOS signaling pathway in a rat model of endotoxin-induced uveitis (EIU). Twenty-eight Wistar albino rats were divided into 4 groups as controls, lypopolysaccharide (LPS) group (5 mg/kg i.p.), LPS + RML group (5 mg/kg i.p and 8 mg/kg orally, respectively) and RML group (8 mg/kg orally). EIU was induced by a single intraperitoneal LPS injection. Histopathological and genetical analyses were performed. In histopathological analysis, LPS caused mild anterior uveitis characterized by increased surface area of iris leaflets and ciliary body due to edema, mild to moderate congestion, and inflammatory infiltrate 6 h following the injection. The pathological findings were reduced by RML. Higher inflammation levels seen in LPS group were significantly reduced in LPS + RML group. Also, HIF-1 α, eNOS and VEGF expressions increased in LPS and decreased in LPS + RML group. RML treatment reversed the changes in the HIF-1α /eNOS/ VEGF signaling pathway in LPS-induced uveitis in rats, preventing the progression of the damage and showed positive effects.

Melatonin Enhances Object Recognition Memory through Melatonin MT1 and MT2 Receptor-Mediated and Non-Receptor-Mediated Mechanisms in Male Mice

Melatonin (MEL) has been reported to have acute enhancing effects on some aspects of cognition. Recently, we revealed that N1-acetyl-5-methoxyquinuramine (AMK), a brain metabolite of MEL, is much more potent than MEL in converting short-term memory (STM) to long-term memory (LTM) with a single administration immediately after the acquisition trial of the novel object recognition (NOR) task. These data suggest that the memory-enhancing effects of MEL may be mediated by mechanisms independent of the activation of MEL MT1 and MT2 receptors. In the present study, we examined the contribution of MT1 and MT2 receptor-mediated and non-receptor-mediated mechanisms to the acute memory-enhancing effects of MEL using NOR task. Mice were administered with either MEL, AMK, or a highly selective MT1/MT2 receptor agonist ramelteon (RAM) immediately after the acquisition trial and the effects of varying doses of these drugs on both STM and LTM performance were compared. We found that both AMK and RAM were more potent than MEL in both facilitating STM and promoting LTM formation. We also found that pretreatment with luzindole, a MT1/MT2 receptor antagonist, markedly suppressed only the effects of RAM. These results suggest that acutely administered MEL enhances NOR memory through both MT1 and MT2 receptor-mediated and non-receptor-mediated mechanisms.

Uykusuzluğu tedavi etmek için kullanılan Ramelteon, osteoporoz oluşumunu azaltabilir

Aim: Melatonin promoted osteoblast differentiation and causes an increase in levels of markers of bone differentiation and proliferation. Ramelteon (RAMEL) activates melatonin receptors and binds to these receptors as non-selective. In this study, we investigated the preventive effects of the melatonin agonist RAMEL on osteoporosis by radiological, histological, and molecularly.Methods: Groups 1: Control, Group 2: Osteoporosis: Overectomized group (OP), Group 3: OP + ramelteon 2 mg/kg, Group 4: OP + ramelteon 4 mg/kg. 24 animals underwent bilateral ovariectomy. RAMEL was administered orally once a day in the prophylactic treatment mode for 8 weeks, 6 weeks after ovariectomy.Results: Fourteen weeks after ovariectomy, there was a significant reduction in femoral bone mineral density (BMD) (g/cm2) in the OP group compared to the control group. Compared to the OP group, RAMEL treatment significantly increased the BMD level (p&amp;lt;0.05). Bone matrix protein 2 (BMP2) and runt-related transcription factor 2 (RUNX2) mRNA levels were significantly lower in the OP group than in the control group (p&amp;lt;0.05). RUNX2 and BMP2 mRNA levels were significantly higher in the RAMEL treatment groups than in the OP group (p&amp;lt;0.05).Conclusion: To take advantage of the peripheral effects of melatonin, RAMEL, a peripheral melatonin agonist, can be used to prevent osteoporosis.

Do peripheral melatonin agonists improve bone fracture healing? The effects of agomelatine and ramelteon on experimental bone fracture

Melatonin improves fracture healing, but the long-term use of melatonin seems impracticable in the treatment of fracture due to side effects caused by hormonal stress on chronological rhythm. Ramelteon (RAMEL) and agomelatine (AGO) are non-selective peripheral melatonin receptor (MT) agonists. This study investigated the effects on bone fracture healing of these MT agonists, which do not affect the central nervous system.The rats were divided into 6 groups, including Group 1 (SHAM): sham operated group; Group 2 (FRACTURE): femoral fracture control; Group 3 (FR + AGO30): femoral fracture + agomelatine 30 mg/kg; Group 4 (FR + AGO60): femoral fracture + agomelatine 60 mg/kg; Group 5 (FR + RAMEL3): femoral fracture + ramelteon 3 mg/kg; and Group 6 (FR + RAMEL6): femoral fracture + ramelteon 6 mg/kg.After 21 days, the rats were subjected to X-ray imaging. Bone healing was evaluated with hematoxylin-eosin (HE) staining. Messenger RNA (mRNA) expressions of bone formation markers, such as bone alkaline phosphatase (ALP), osteocalcin (OC), and osteopontin (OP), were evaluated by real-time polymerase chain reaction (RT-PCR) and with immunohistochemistry (IHC) staining.The radiographic fracture healing scores were statistically significantly higher in the FR + AGO60 group and the FR + RAMEL3 group than in the FRACTURE group. The histopathology and molecular results supported the radiographic results.It was shown that agomelatine and ramelteon increase bone fracture healing, leading to the conclusion that a preference for agomelatine, an antidepressant, and ramelteon, a sleep aid, will increase bone fracture healing in patients with fractures.

Melatonergic agonist regulates circadian clock genes and peripheral inflammatory and neuroplasticity markers in patients with depression and anxiety

ObjectiveCircadian dysfunction is a core manifestation and a risk factor for psychiatric disorders. Ramelteon (RMT), a melatonin receptor agonist, has been shown to induce sleep phase shifts and has been used to normalize sleep onset time. RMT has been used in sleep disorders, depression and anxiety. In this study, we aimed to investigate the effects of RMT in regulating gene expression profiles of the circadian clock and peripheral markers of inflammation and neuroplasticity. MethodsSixteen patients with a diagnosis of primary insomnia comorbid with depression and anxiety and ten healthy controls were recruited in an 8-week open-label trial. The patients with primary insomnia received RMT 8 mg/day. The morning expression profiles of 15 core clock genes from peripheral blood mononuclear cells (PBMCs), urine and plasma levels of melatonin and its metabolite levels, and plasma inflammatory markers and neurotrophin levels were evaluated at baseline, 4th and 8th week of RMT treatment. ResultsRMT treatment was associated with significant clinical improvement in depression scores at 8th week (Hamilton depression rating scale scores (Mean ± SEM) from 21.5 ± 2.44 to 14.31 ± 2.25, p ≤ 0.05). The overall poor sleep quality (Pittsburgh sleep quality index) of the patient group significantly improved (p ≤ 0.05) following RMT treatment. The mRNA level analysis showed a significant association between RMT treatment and alterations of the nine core circadian genes (CLOCK, PER1, PER2, CRY1, CRY2, NR1D1, NR1D2, DEC1 and TIMELESS) in the patient group when compared with the control group (p ≤ 0.05). Compared with the controls, the patient group had a decrease in neurotrophins (brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor and beta-nerve growth factor; p ≤ 0.05) but an increase in pro-inflammatory cytokine levels (interleukin-6, interleukin-1b, tumour necrosis factor-alpha and interferon gamma; p ≤ 0.05); RMT treatment normalized the levels of neurotrophins and cytokine levels. ConclusionRMT treatment is able to restore phase-shifted melatonin markers, normalized the altered expression of the circadian genes, the levels of inflammatory cytokines and neurotrophins in patients with insomnia comorbid anxiety and depression.

Crystal Structures of Two Important Pharmaceuticals Solved by 3D Precession Electron Diffraction Tomography

The crystal structures of two important marketed pharmaceuticals, namely, ramelteon (RAM) and tolvaptan (TOL), were determined for the first time using 3D precession electron diffraction tomography (PEDT) on 500 nm-sized crystals. The results were compared with the same structures determined by single-crystal X-ray diffraction on subsequently grown 50–200 μm single crystals, indicating a good match of molecular conformation, crystal packing, and unit cell parameters. The X-ray crystal structures were used to validate the developed workflow of data acquisition and structure solution with electron diffraction. This study highlights that 3D PEDT alone is able to provide accurate crystal structures from pharmaceutical nanocrystals that will suffice for most practical applications when no larger crystals can be grown.

Melatonin, Insomnia and the Use of Melatonergic Drugs

Due to inconsistency among reports on the therapeutic efficacy of melatonin, attention has been focused on the development of more potent melatonin analogues with prolonged effects. Melatonergic drugs, ramelteon and agomelatine have been effective in treating either sleep disorders or sleep disturbances associated with depressive disorders. MT 1 and MT 2 melatonergic receptor agonist, ramelteon, was found effective in increasing total sleep time and sleep efficiency, and in reducing sleep latency in patients with insomnia. No reduction in its efficacy was found even after 6-12 months of continuous use. The mechanism of sleep promoting action of ramelteon is entirely different from that of conventional hypnotics that are in use today. Ramelteon's use is not associated with any adverse effects even after six months to one year after its continuous usage. Another melatonergic drug, agomelatine, has also been found effective in improving sleep efficiency and quality, and this action of agomelatine is suggested to be one of the major mechanism by which agomelatine ameliorates depressive symptoms in patients with major depressive disorders and bipolar disorders.

MT1 Melatonin Receptors Mediate Somatic, Behavioral, and Reproductive Neuroendocrine Responses to Photoperiod and Melatonin in Siberian Hamsters (Phodopus sungorus)

Environmental day length drives nocturnal pineal melatonin secretion, which in turn generates or entrains seasonal cycles of physiology, reproduction, and behavior. In mammals, melatonin (MEL) binds to a number of receptor subtypes including high-affinity (MT1 and MT2) and low-affinity (MT3, nuclear orphan receptors) binding sites, which are distributed throughout the central nervous system and periphery. The MEL receptors that mediate photoperiodic reproductive and behavioral responses to MEL have not been identified in a reproductively photoperiodic species. Here I tested the hypothesis that MT1 receptors are necessary and sufficient to engage photoperiodic responses by challenging male Siberian hamsters (Phodopus sungorus), a species that does not express functional MT2 receptors, with ramelteon (RAM), a specific MT1/MT2 receptor agonist. In hamsters housed in a long-day photoperiod, late-afternoon RAM treatment inhibited gonadotropin secretion, induced gonadal regression, and suppressed food intake and body mass, mimicking effects of MEL. In addition, chronic (24 h/d) RAM infusions were sufficient to obscure endogenous MEL signaling, and these treatments attenuated gonadal regression in short days. Together, the outcomes indicate that signaling at the MT1 receptor is sufficient and necessary to mediate the effects of photoperiod-driven changes in MEL on behavior and reproductive function in a reproductively photoperiodic mammal.

Effect of Uridine (U), Melatonin (MLT) and Ramelteon (RMT) on edema formation following traumatic brain injury (TBI) in rats

TBI is a significant cause of disability and death. We investigated post‐treatment with U (a pyrimidine) and MLT (a pineal indoleamine hormone and free radical scavenger), individually and in combination, on regional brain edema following TBI via fluid percussion. Male rats underwent craniotomy and were divided into groups: Sham+Vehicle (V), Sham+Treatment (TX), TBI+V [moderate TBI on right (impacted) side], and TBI+TX [received i.p. (mg/Kg): U (16 &amp; 32), MLT (100 &amp; 200) or U (16/32) + MLT (200)]. After 48 hrs, edema (%) was determined on both sides. Impacted side edema was higher in TBI+V vs Sham+V and treatments did not affect edema levels in Sham+TX vs Sham. Our previous studies showed that U (16 and 32) and MLT (200), individually reduced impacted side striatal edema vs TBI+V. Combination U (32) + MLT (200) reduced edema in impacted and non‐impacted hippocampus and striatum vs TBI+V. U (16) + MLT (200) also reduced edema in impacted hippocampus, and impacted and non‐impacted striatum. To determine whether the neuroprotection of MLT in this model involved MT1 and MT2 receptors in addition to its anti‐oxidant properties, we tested RMT (10 and 20 mg/Kg, i.p.), a selective MT1/MT2 receptor agonist. RMT failed to reduce edema levels in cortex, hippocampus and striatum on impacted as well as non‐impacted side vs TBI+V. Thus, neuroprotection by MLT in this TBI model is not likely MT1/MT2 receptor‐mediated.