Exogenous Melatonin Administration Research Articles

Assessing the Effect of Exogenous Melatonin on Orthodontic Tooth Movement.

To examine the effect of orthodontic tooth movement on experimental Wistar rats by synthesizing melatonin formulation for administration and conducting serological analysis of alkaline phosphatase (ALP) and melatonin, along with histological evaluation and immunohistochemistry analysis of ALP and interleukin-6 (IL-6) in both control and experimental groups. Nine male Wistar rats were randomly divided into negative (n = 3), positive control (n = 3), and experimental groups (n = 3). Endogenous melatonin levels (pg/mL) were assessed, and an orthodontic force of 10 cN was applied to positive control and experimental groups using a ligature wire. The experimental group received a daily dose of 10 mg/kg melatonin via intraperitoneal injection. After eight weeks, blood samples and radiographs were collected, and mandible sections were prepared for histopathological and immunohistochemical evaluation. The radiographic evaluation shows minimal orthodontically induced tooth movement in comparison to the positive control group. In serological analysis, ALP was found to be increased in rats under the melatonin group. And, in the immunohistochemical evaluation, ALP was found to be increased in the melatonin group, whereas IL-6 was found to be decreased in the same (P= 0.027). The study elucidates that the administration of exogenous melatonin during orthodontic tooth movement in Wistar rats induces bone formation and inhibits resorption, eventually decelerating the process of orthodontic tooth movement. Our study emphasizes melatonin's dualistic role in stimulating bone production and suppressing resorption, offering potential therapeutic clinical implications in orthodontics.

The effect of exogenous melatonin administration before superovulation on embryo yield in Assaf ewes.

The aim of this study was to determine the effect of exogenous melatonin administration on transferable embryos by increasing total antioxidant status before superovulation in Assaf ewes. Selected ewes were randomly divided into two equal groups: melatonin (n = 9) and control (n = 9). In the melatonin group, a melatonin implant (18 mg melatonin, Regulin®, Ceva, Turkey) was placed under the skin of the ear 7 days prior to insertion of the progesterone-containing sponge. In the control group, a physiological saline solution was injected under the skin of the ear on the same day. The same superovulation protocol was used in both groups. In addition, blood samples for determination of Glutathione peroxidase, superoxide dismutase, total antioxidant status and total oxidant status concentrations were collected on five different days, including the day of melatonin implant placement (Day-7), vaginal sponge insertion (Day 0), vaginal sponge removal (Day 11), mating (Day 12-13) and uterine flushing (Day 19). Embryos were collected by laparotomy on the 7th day after mating. Uterine flushing taken into petri dishes were scanned under a stereomicroscope, and the quality and developmental stages of the embryos were recorded. In the study, total corpus luteum count and total cell count were found to be higher in the control group than in the melatonin group (p < .05). When the results were evaluated in terms of oxidative stress index, a negative correlation was found between the total number of corpus luteum, number of cells obtained, count of transferable embryos and number of Grade 1 embryos on Day 0. There was also a positive correlation oxidative stress index and the number of unfertilized oocytes on Day-7. As a result, exogenous melatonin administration prior to superovulation during the breeding season is thought to have a negative effect on embryo yield and quality. Therefore, the use of exogenous melatonin in MOET studies during the breeding season is recommended to be investigated in new studies.

Exogenous melatonin's effect on salivary cortisol and amylase: A randomized controlled trial.

This study aimed to examine the effect of acute exogenous melatonin administration on salivary cortisol and alpha-amylase (sCort and sAA) as representatives of the HPA axis and the sympathetic nervous system, respectively. A single-dose prolonged-release melatonin (2 mg) or a placebo tablet was given to healthy volunteers (n = 64) at 20:00 h in a crossover design. The saliva was collected at six time points (20:00, 21:00, awakening, 30 min after awakening, 10:00, and 12:00 h) and was measured for sCort, sAA, and salivary melatonin (sMT) levels. Pulse rates and sleep parameters were also collected. Melatonin was effective in improving sleep onset latency by 7:04 min (p = .037) and increasing total sleep time by 24 min (p = .006). Participants with poor baseline sleep quality responded more strongly to melatonin than participants with normal baseline sleep quality as they reported more satisfaction in having adequate sleep (p = .017). Melatonin administration resulted in higher sCort levels at awakening time point (p = .023) and a tendency of lower sAA levels but these were not significant. Melatonin ingestion at 20:00 h resulted in a marked increase in sMT levels at 21:00 h and remained higher than baseline up to at least 10:00 h (p < .001). Melatonin increases sCort levels at certain time point with a tendency to lower sAA levels. These opposing effects of melatonin suggested a complex interplay between melatonin and these biomarkers. Also, the results confirmed the positive acute effect of a single-dose melatonin on sleep quality.

Potential of exogenous melatonin administration to mitigate heat stress induce pathophysiology of chicken

Melatonin (MT) is an amine hormone secreted by the body that has antioxidant and anti-inflammatory properties. The aim of this study was to investigate pathophysiological protection of MT in heat-stressed chickens. By modelling heat-stressed chickens and treating them with MT. After 21 days of administration, serum antioxidant enzymes, biochemical indices, inflammatory cytokine and heat-stress indices were detected, along with cardiopulmonary function indices and histological observations in chickens. The results show heat-stress induced a decrease (P <0.05) in body weight and an increase in body temperature, which was reversed after MT intervention. Treatment with MT inhibited (P <0.05) the secretion of pro-inflammatory factors interleukin-1β, interleukin-6, tumor necrosis factor α, serum heat shock protein 70, corticosterone, and elevated (P <0.05) the levels of biochemical factors total protein, albumin, globulin, and increased (P <0.05) the activities of antioxidant enzymes superoxide dismutase, glutathione peroxidase and catalase in chicken serum caused by heat stress, and the best effect was observed with the medium dose of MT. The heat-stress caused cardiac atrophy and pulmonary congestion, decreased (P <0.05) the cardiac function indices creatine kinase isoenzyme, cardiac troponin I, angiotensin receptor I, creatine kinase and lung function indices myeloperoxidase, angiotensin-II, heat shock factor I, and increased (P <0.05) the lung vascular endothelial growth factor II. Sections of the heart and lungs after administration of MT were observed to be more complete with more normal tissue indices. At the same time, compared with heat stress, heart and lung function indices of grade chickens after MT administration were significantly (P <0.05)reduced and tended to normal levels, and the best effect was observed in the medium-dose MT. In conclusion, heat stress can cause pathophysiological damage in chickens, and 1 mg/kg/d of exogenous melatonin can attenuate this adverse effect.

New Perspectives on the Role and Therapeutic Potential of Melatonin in Cardiovascular Diseases.

Cardiovascular diseases (CVDs) are the leading cause of death and disability worldwide. It is essential to develop novel interventions to prevent/delay CVDs by targeting their fundamental cellular and molecular processes. Melatonin is a small indole molecule acting both as a hormone of the pineal gland and as a local regulator molecule in various tissues. It has multiple features that may contribute to its cardiovascular protection. Moreover, melatonin enters all cells and subcellular compartments and crosses morphophysiological barriers. Additionally, this indoleamine also serves as a safe exogenous therapeutic agent. Increasing evidence has demonstrated the beneficial effects of melatonin in preventing and improving cardiovascular risk factors. Exogenous administration of melatonin, as a result of its antioxidant and anti-inflammatory properties, has been reported to decrease blood pressure, protect against atherosclerosis, attenuate molecular and cellular damage resulting from cardiac ischemia/reperfusion, and improve the prognosis of myocardial infarction and heart failure. This review aims to summarize the beneficial effects of melatonin against these conditions, the possible protective mechanisms of melatonin, and its potential clinical applicability in CVDs.

Long-Term Impacts of Exogenous Melatonin Administration in Patients: An Integrative Review

Long-Term Impacts of Exogenous Melatonin Administration in Patients: An Integrative Review

Optimizing timing and dose of exogenous melatonin administration in neuropsychiatric pediatric populations: a metanalysis on sleep outcomes

Optimizing timing and dose of exogenous melatonin administration in neuropsychiatric pediatric populations: a metanalysis on sleep outcomes

Melatonin enhances captopril mediated cardioprotective effects and improves mitochondrial dynamics in male Wistar rats with chronic heart failure

Mitochondrial dysfunction is a recent emerging research scope that proved to be involved in many cardiovascular diseases culminating in chronic heart failure (CHF), which remains one of the primary causes of morbidity and mortality. This study investigated the added cardio-protective effects of exogenous melatonin administration to conventional captopril therapy in isoproterenol (ISO) exposed rats with CHF. Five groups of Wistar rats were recruited; (I): Control group, (II): (ISO group), (III): (ISO + captopril group), (IV): (ISO + melatonin group) and (V): (ISO + melatonin/captopril group). Cardiac function parameters and some oxidant, inflammatory and fibrotic markers were investigated. Moreover; mRNA expression of mitochondrial mitophagy [parkin & PTEN induced kinase 1 (PINK1)], biogenesis [Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)], fusion [mitofusin 2 (Mfn2)] and fission [dynamin-related protein 1 (DRP-1)] parameters in rat’s myocardium were evaluated. Rats’ myocardium was histo-pathologically and immunohistochemically evaluated for Beclin1 and Sirt3 expression. The present study revealed that captopril and melatonin ameliorated cardiac injury, oxidative stress biomarkers, and pro-inflammatory cytokines in ISO-exposed rats. These protective effects could be attributed to mitochondrial dynamic proteins control (i.e. enhanced the mRNA expression of parkin, PINK1, PGC-1α and Mfn2, while reduced DRP-1 mRNA expression). Also, Beclin1 and Sirt3 cardiac immunoreactivity were improved. Combined captopril and melatonin therapy showed a better response than either agent alone. Melatonin enhanced myocardial mitochondrial dynamics and Sirt3 expression in CHF rats and may represent a promising upcoming therapy added to conventional heart failure treatment.

The effects of pinealectomy and melatonin treatment in acrylamide-induced nephrotoxicity in rats: Antioxidant and anti-inflammatory mechanisms

ObjectiveAcrylamide (AA) is toxic and forms in food that undergoes high-temperature processing. This study aimed to investigate the effects of AA-induced toxicity on renal tissue in pinealectomized rats and the possible protective effect of exogenous Melatonin (ML) administration. Materials and MethodsSixty rats were randomized into 6 groups (n = 10): Sham, Sham+AA, Sham+AA+ML, PX, PX+AA, and PX+AA+ML. Sham and pinealectomized rats received AA (25 mg/kg/day orally) and ML (0.5 ml volume at 10 mg/kg/day, intraperitoneal) for 21 days. ResultsThe results showed that malondialdehyde (MDA), total oxidant status (TOS), oxidative stress index (OSI), tumor necrosis factor-α (TNF-α), and interleukin 1β (IL-1β) levels of the kidney and urea and creatinine levels of serum in the PX (pinealectomy)+AA group were more increased than in the Sham+AA group. In addition, glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and total antioxidant status (TAS) levels decreased more in the PX+AA group than in the Sham+AA group. Also, we observed more histopathologic damage in the PX+AA group. On the other hand, up-regulation of kidney tissue antioxidants, down-regulation of tissue oxidants, and improvement in kidney function were achieved with ML treatment. Also, histopathological findings such as inflammatory cell infiltration, shrinkage of glomeruli, and dilatation of tubules caused by AA toxicity improved with ML treatment. ConclusionML supplementation exhibited adequate nephroprotective effects against the nephrotoxicity of AA on pinealectomized rat kidney tissue function by balancing the oxidant/antioxidant status and suppressing the release of proinflammatory cytokines.

EFFECTIVENESS OF MELATONIN AND RESVERATROL COMBINED ADMINISTRATION IN ROUND-THE-CLOCK ILLUMINATION WITH HIGH-CALORIE CARBOHYDRATE-LIPID DIET

The purpose of this experiment was to investigate the combined effect of exogenous melatonin and resveratrol on the serum melatonin content in rats exposed to 30 day round-the-clock lighting (RCL) and kept on a high-calorie carbohydrate-lipid diet (HCCLD, 20% fructose solution, and standard chow). The combination of exogenous melatonin and resveratrol was administered for 60 days to 35 white male rats. Exogenous melatonin and resveratrol were administered daily during the last 30 days of the experiment intragastrically in a dose of 5 mg/kg (both). The findings obtained have revealed the combined effect of RCL and HCCLD reduced the serum melatonin content to 7.1±0.7 pg/ml that is 77.7% (p&lt;0.001) lower than the control values (31.8±2.5 pg/ml). Applying exogenous melatonin restored the concentration of this hormone in the blood serum to normal values, 28.4±1.6 pg/ml. Resveratrol administration increased the melatonin content to 13.6±1.0 pg/ml, i.e. by 91.5% (p&lt;0.001). The combined administration of exogenous melatonin and resveratrol increased the concentration of melatonin in the blood serum to 32.3±2.0 pg/ml. It can be concluded that the combined effect of exogenous melatonin and resveratrol under RCL and HCCLD is more effective in correcting hypomelatoninemia compared to the effect of the compounds used separately.

Structural and organometric changes of the uterus in conditions of dark deprivation

The effect of 30-day dark deprivation (light-dark cycle 24/0 h, artificial illumination 300 Lux) and 14-day correction with melatonin on the endometrium of the uterus was studied in an experiment on mongrel females of 4 months of age. It was found that 30-day dark deprivation leads to hyperplastic processes of the endometrium: an increase in the number of uterine glands (by 18.9 % p 0.05), thickening of the endometrium (by 12.5 %, p 0.05). Morphometric characteristics of the endometrium: single-layer columnar epithelium of the endometrium and uterine glands were corrected by administration of exogenous melatonin for 14 days.

Melatonin Ameliorates Neuropsychiatric Behaviors, Gut Microbiome, and Microbiota-Derived Metabolites in Rats with Chronic Sleep Deprivation

With the increasing prevalence of sleep deprivation (SD)-related disorders, the effective treatment of sleep disorders has become a critical health research topic. Thus, we hypothesized and investigated the effectiveness of a 3-week melatonin intervention on neuropsychiatric behavioral responses mediated throughout melatonin receptors, gut microbiota, and lipid metabolites in rats with chronic SD. Eighteen 6-week-old Wistar rats were used and divided into the control grup (C, n = 6), SD group (n = 6), and melatonin-supplemented group (SDM, n = 6). During weeks 0 to 6, animals were provided with the AIN-93M diet and free access to water. Four-week chronic SD was conducted from weeks 7 to 10. Exogenous melatonin administration (10 mg/kg BW) was injected intraperitoneally 1 h before the daily administration of SD for 3 weeks in the SDM group. SD rats exhibited anxiety-like behavior, depression-like behavior, and cognitive impairment. Exogenous melatonin administration ameliorated neuropsychiatric behaviors induced by chronic SD. Analysis of fecal metabolites indicated that melatonin may influence brain messaging through the microbiota–gut–brain axis by increasing the production of short-chain fatty acids (SCFA) and decreasing the production of secondary bile acids (SBA). Four-week SD reduced the cerebral cortex expression of MT1, but not in the colon. Chronic SD led to anxiety and depression-like behaviors and cognitive decline, as well as the reduced intestinal level of SCFAs and the enhanced intestinal level of SBAs in rats. In this work, we confirmed our hypothesis that a 3-week melatonin intervention on neuropsychiatric behavioral response mediated throughout melatonin receptors, gut microbiota, and lipid metabolites in rats with chronic SD.

Melatonin as a promising therapeutic intervention for restoring ovarian function in letrozole-induced polycystic ovary syndrome rats

Polycystic ovary syndrome (PCOS) is a common hormonal disorder that affects women of reproductive age and is characterized by multiple ovarian cysts, irregular menstrual cycles, and excessive androgen hormone production. The present study aimed to investigate the therapeutic efficacy of melatonin in alleviating PCOS-induced alterations in female Wistar rats. PCOS was induced in female albino rats by administering letrozole at a dose of 1 mg/kg for 21 days. A total of 24 rats were randomly selected and divided into four groups: group I (normal control), group II (melatonin treatment), group III (letrozole treatment), and group IV (melatonin therapy for PCOS rats). Physical parameters (body and uterus weight), hormone profile (LH and FSH), and steroidogenic enzyme activities and an oral glucose test were assessed using standard methods. Histological analysis was performed using hematoxylin and eosin staining. The results demonstrated that exogenous melatonin administration significantly improved PCOS symptoms in rats, including reduced body weight gain, changes in organ weight/body weight index, blood glucose level, percentage diestrus phase, testosterone, estradiol, progesterone, and LH/FSH ratio, as well as 3β-HSD and 17β-HSD enzyme activity. Histopathological findings revealed well-developed follicles, decreased cystic follicles, and increased antral follicles, Graafian follicles, and corpus luteum in PCOS rats treated with melatonin. These positive outcomes suggest that exogenous melatonin may hold promise as a valuable remedy for PCOS conditions in female rats. Further research is warranted to fully elucidate the underlying mechanisms and potential clinical applications of melatonin in the context of PCOS.

Effects of Exogenous Melatonin on Colon Glial Cells in Experimental Desynchronosis

The effect of exogenous and endogenous melatonin on GFAP and S-100 positive cells of the colon mucosa of rats kept under different lighting conditions was studied.The aim was to estimate the effect of melatonin on the structural and functional characteristics of colon glial cells in normal conditions and in experimental desynchronosis.Material and methods. The study was conducted on laboratory male Wistar rats (n=72), 2-months old, weighing 180–200 g, divided into 6 groups 12 rats in each. Group I consisted of animals treated in natural light conditions; Group II – rats treated in natural light conditions, receiving synthetic melatonin (Melaxen, Unipharm, Inc., USA) ad libitum at a concentration of 4 mg/l with drinking water; Group III – animals treated in constant darkness; Group IV – animals treated in constant darkness and received melatonin; Group V consisted of animals treated under constant lighting conditions; Group VI included rats treated in constant lighting conditions and received melatonin. Astrocytes were identified using an indirect immunohistochemical method using polyclonal antibodies to glial fibrillary acidic protein (Dako, Germany 750 µg/ml) and protein S-100 (Spring Bio Science USA 1:300). Cells were counted using a Carl Zeiss Axio Scope A1 microscope at 400 magnification and SigmaScan Pro 5 software. Statistical processing was carried out using the MS Excel and Statistica 17 programs.Results. The number of GFAP positive cells decreased in groups III and V. Conditions II and VI resulted in a decrease in the number of gliocytes. In group IV, the administration of melatonin led to an increase in the number of studied cells. A significant increase in the optical density of GFAP in colon gliocytes was observed only when rats were treated under constant lighting conditions. The number of S-100 positive cells decreased in groups III and II. Conditions V and IV led to an increase in the number of S-100 positive cells. The optical density of S-100 does not depend on photoperiod.Conclusion. S-100B and GFAP positive glial cells of the colon respond both to changes in photoperiod and to the administration of exogenous melatonin. In particular, under constant dark conditions, the number of GFAP and S-100B positive cells decreases. The obtained data can be used in the elaboration of new therapeutic approaches to the treatment of intestinal diseases.

The relationship between anesthesia and melatonin: a review.

Introduction: This comprehensive review delves into the intricate and multifaceted relationship between anesthesia and melatonin, aiming to provide essential insights for perioperative clinical anesthesiologists and stimulate interest in related research. Anesthesia and surgery have the potential to disrupt melatonin secretion, leading to sleep disorders, postoperative neurocognitive dysfunction and other symptoms. In comparison to previous reviews, this review provides a comprehensive summary of the various aspects linking melatonin and anesthesia, going beyond isolated perspectives. It explores the potential benefits of administering melatonin during the perioperative period, including alleviating anxiety, reducing pain, enhancing perioperative sleep quality, as well as demonstrating immunomodulatory and anti-tumor effects, potentially offering significant advantages for cancer surgery patients. Recent Findings: Anesthesia and surgery have a significant impact on melatonin secretion, the hormone crucial for maintaining circadian rhythms. These procedures disrupt the normal secretion of melatonin, leading to various adverse effects such as sleep disturbances, pain, and postoperative neurocognitive dysfunction. However, the administration of exogenous melatonin during the perioperative period has yielded promising results. It has been observed that perioperative melatonin supplementation can effectively reduce anxiety levels, improve pain management, enhance the quality of perioperative sleep, and potentially decrease the occurrence of postoperative delirium. In recent years, studies have found that melatonin has the potential to improve immune function and exhibit anti-cancer effects, further underscoring its potential advantages for patients undergoing cancer surgery. Summary: In summary, melatonin can serve as an adjuvant drug for anesthesia during the perioperative period. Its administration has demonstrated numerous positive effects, including anti-anxiety properties, sedation, analgesia, improved postoperative sleep, and the potential to reduce the incidence of postoperative delirium. Furthermore, its immune-modulating and anti-tumor effects make it particularly valuable for cancer surgery patients. However, further studies are required to determine the optimal dosage, long-term safety, and potential adverse reactions associated with melatonin administration.

Efecto de la administración exógena de Melatonina sobre la Espermatogénesis en un modelo de rata con estrés crónico impredecible

This study investigated the hormonal, inflammatory, oxidant–antioxidant, and histopathological effects of exogenous Melatonin administration on Spermatogenesis in rats' chronic unpredictable stress model (CUSM). In the study, stress caused a decrease in follicle stimulating–hormone (FSH), luteinizing hormone (LH), Testosterone, Melatonin, Glutathione (GSH), Glutathione peroxidase (GSH–Px), catalase, interleukin 10 (IL–10) levels and motility, and an increase in Corticosterone, nuclear factor kappa beta (NF–kB), tumor necrosis factor–alpha (TNF–α), interleukin 1 beta (IL–1β), interleukin 6 (IL–6), abnormal sperm, dead/live sperm ratio and exogenous Melatonin reduced inflammatory cytokines and oxidative stress and improved spermatological parameters (P&lt;0.05). Melatonin also partially corrected stress–induced changes in testicular morphology. As a result, using Melatonin in rats with CUSM may be effective in improving spermatological parameters through anti–inflammatory and antioxidant mechanisms.

Melatonin protects against ketorolac induced gastric mucosal toxic injuries through molecular mechanism associated with the modulation of Arylakylamine N-Acetyltransferase (AANAT) activity

Ketorolac tromethamine (KT), is a widely used non-steroidal anti-inflammatory drug (NSAID) for treating moderate to severe pain. However, the use of KT has been restricted due to its highly toxic attributes that lead to severe gastric ulceration and bleeding. The protective effects of exogenous melatonin (MT) has been reported in conditions associated with gastro-intestinal disorders. This study aims at exploring the role of gastric endogenous MT level and it's metabolizing enzyme AANAT, at the onset of ketorolac mediated toxicities in the gastric mucosa. Gastric mucosal damage was induced in experimental rats by oral administration of graded doses of KT, where 50 mg/kg b.w. of KT was observed to incur maximum gastric lesions. However, gastric damages were found to be protected in rats, pre-treated with 60 mg/kg b.w. of MT. Post-sacrifice, mean ulcer index, oxidative status, total melatonin levels and enzyme activities associated with MT biosynthesis and catabolism were estimated. The results reveal that KT decreases AANAT activity with a concomitant decline in endogenous MT level which cumulatively aggravates gastric toxicity. Moreover, exogenous MT administration has been found to be protective in ameliorating this ulcerogenic process in rats, challenged with KT. Biochemical and histo-pathological observations revealed the reduction in oxidative stress level and replenishment of depleted gastric MT levels in MT pre-treated animals, which might be the causative factors in conferring protection to the gastric tissues and residing mitochondria. The results revealed a correlation between depleted gastric MT level and ulcer formation, which unveiled a novel ulcerogenic mechanism. This may bring forth future therapeutic relevance for treating patients suffering from KT mediated acute gastric toxicities.

Reproductive performance of hair ewes and rams implanted with melatonin previous to the anestrus season in northwest Mexico.

Ovine reproductive behavior depends on annual photoperiodic cycle and its impact on endogenous melatonin secretion. In this regard, exogenous melatonin administration previous to the physiological anestrus period could modify the reproductive performance of sheep in the northwest of Mexico. Two independent studies were performed to evaluate such hypothesis in hair sheep implanted with melatonin prior to the anestrus season in latitudes 24° and 25° of Mexico. Study 1 involved 15 rams assigned to one of three treatments receiving 0mg (n=5), 18mg (n=5), or 36mg (n=5) of melatonin subcutaneously. Study variables were measured monthly since implantation (d0) and included testosterone concentration, scrotal circumference, mass motility, individual motility, and sperm concentration. Study 2 included 50 ewes assigned to one of two treatments receiving 0mg (n=25) or 18mg (n=25) of melatonin subcutaneously. In ewes, progesterone concentration and the frequency of females in anestrus were measured during the implantation (-30d), as well as at the beginning (0d) and at the end (45d) of the mating period, while pregnancy rate was determined by ultrasonography 45d after. Continuous variables were analyzed using a mixed effects model considering treatment, time, and the treatment by time interaction as fixed effects. Animal nested within treatment was the random effect. Binary variables were analyzed using the chi-square test. In males, melatonin improved testosterone and sperm concentrations (P<0.05), while in females, a 28% higher pregnancy rate was observed in implanted ewes (P<0.05). Therefore, melatonin enhanced reproductive parameters in both sexes and its exogenous administration previous to the anestrus season in northwest Mexico could be more effective in rams.

Morphology of sustentocytes (Sertoli cells) with premature aging caused by light desynchronosis

The effect of 30-day dark deprivation (light-dark cycle 24/0 h, artificial illumination 300 Lux) on the morphofunctional state of the testes was studied using morphological and morphometric analysis of histological preparations of white mongrel male rats 4 months of age. The level of follicle-stimulating hormone in blood serum was assessed by enzyme immunoassay. It was found that 30-day dark deprivation increases the level of follicle-stimulating hormone in the blood serum. Morphological changes in the testes were characterized by a decrease in the area of Sertoli cells and their nuclei, the thickness of the spermatogenic epithelium. The hormonal background and morphofunctional state of the testes were corrected by the administration of exogenous melatonin for 14 days.

Melatonin in Newborn Infants Undergoing Surgery: A Pilot Study on Its Effects on Postoperative Oxidative Stress

Surgery is frequently associated with excessive oxidative stress. Melatonin acts as an antioxidant and transient melatonin deficiency has been described in neonatal surgical patients. This randomized, blinded, prospective pilot study tested the hypothesis that oral melatonin supplementation in newborn infants undergoing surgery is effective in reducing perioperative oxidative stress. A total of twenty-three newborn infants requiring surgery were enrolled: 10 received a single dose of oral melatonin 0.5 mg/kg in the morning, before surgery (MEL group), and 13 newborns served as the control group (untreated group). Plasma concentrations of melatonin, Non-Protein-Bound Iron (NPBI), Advanced Oxidation Protein Products (AOPP), and F2-Isoprostanes (F2-IsoPs) were measured. Both in the pre- and postoperative period, melatonin concentrations were significantly higher in the MEL group than in the untreated group (preoperative: 1265.50 ± 717.03 vs. 23.23 ± 17.71 pg/mL, p < 0.0001; postoperative: 1465.20 ± 538.38 vs. 56.47 ± 37.18 pg/mL, p < 0.0001). Melatonin significantly increased from the pre- to postoperative period in the untreated group (23.23 ± 17.71 vs. 56.47 ± 37.18 pg/mL; pg/mL p = 0.006). In the MEL group, the mean blood concentrations of NPBI, F2-IsoPs, and AOPP significantly decreased from the pre- to the postoperative period (4.69 ± 3.85 vs. 1.65 ± 1.18 micromol/dL, p = 0.049; 128.40 ± 92.30 vs. 50.25 ± 47.47 pg/mL, p = 0.037 and 65.18 ± 15.50 vs. 43.98 ± 17.92 micromol/dL, p = 0.022, respectively). Melatonin concentration increases physiologically from the pre- to the postoperative period, suggesting a defensive physiologic response to counteract oxidative stress. The administration of exogenous melatonin in newborn infants undergoing surgery reduces lipid and protein peroxidation in the postoperative period, showing a potential role in protecting babies from the deleterious consequences of oxidative stress.