Ageing,opioid analgesia and the pineal gland

The effects of ageing on day-night rhythms of analgesia was examined with young (1–2 months), mature (8–12 months) and old (20–30 months) mice. Significant age-related declines were observed both in the absolute levels and diel rhythms of morphine analgesia, with the most pronounced changes occuring at night. Administration of the pineal hormone, melatonin, augmented day-time levels of analgesia in all age classes and reversed the age-related decline in nocturnal morphine analgesia in old mice. Inhibition of pineal function in young mice by either exposure to light pulses or treatment with benserazide mimicked the effects of ageing on nocturnal morphine analgesia. These findings suggest that the pineal gland and melatonin are involved in modulating diel rhythms of analgesia and have an influential role on age-related changes in opioid responses.     

Comparative assessment of the effects of salinomycin and monensin on the biodistribution of lead and some essential metal ions in mice,subjected to subacute lead intoxication

In this study, we present a comparative assessment of the effects of two polyether ionophorous antibiotics (monensin and salinomycin) on the concentrations of lead (Pb), cooper (Cu), zinc (Zn) and iron (Fe) in the kidneys, spleen, liver and brain of Pb-intoxicated animals. Our data demonstrated that the intoxication of ICR male mice with Pb salt resulted in a significant accumulation of Pb in all studied organs of the mice compared to the untreated control animals. The biodistribution of the toxic metal was in the order kidneys > spleen > liver > brain. The treatment of the Pb-intoxicated animals with tetraethylammonium salts of monensic and salinomycinic acids significantly decreased the concentration of the toxic metal ion compared to the toxic control. The effect varied in the interval 38% (for kidneys) to 52% (for brain) compared to the toxic control group (Pb). The tetraethylammonium salt of salinomycinic acid was more effective in reducing the Pb concentration in the brain of the Pb-treated mice compared to monensin. Pb-intoxication did not affect significantly the Zn endogenous concentration compared to the normal values. The treatment of ICR male mice with Pb-salt decreased the Cu concentration in the spleen and increased the Cu concentration in the liver compared to the untreated control animals. The detoxification of the Pb-intoxicated mice with tetraethylammonium salts of salinomycinic and monensic acids restored the Cu concentration in the spleen, but did not affect the Cu levels in the liver. The Pb-intoxication of the ICR mice resulted in a significant decrease of the Fe-concentration in the spleen and liver compared to the untreated control animals. The administration of the tetraethylammonium salts of salinomycinic and monensic acids to the Pb-treated animals restored the levels of Fe in both organs.     

Age-associated changes in protein oxidation and proteasome activities in rat brain: modulation by antioxidants

The free radical theory of ageing postulates that age-associated neurodegeneration is caused by an imbalance between pro-oxidants and antioxidants resulting in oxidative stress. The current study showed regional variation in brain susceptibility to age-associated oxidative stress as shown by increased lipofuscin deposition and protein carbonyl levels in male rats of age 15-16 months compared to control ones (3-5 months). The hippocampus is the area most vulnerable to change compared to the cortex and cerebellum. However, proteasomal enzyme activity was not affected by age in any of the brain regions studied. Treatment with melatonin or coenzyme Q10 for 4 weeks reduced the lipofuscin content of the hippocampus and carbonyl level. However, both melatonin and coenzyme Q10 treatments inhibited beta-glutamyl peptide hydrolase activity. This suggests that these molecules can alter proteasome function independently of their antioxidant actions.     

Protective effect of exogenous melatonin on testicular histopathology and histomorphometry of adult rats with domperidone-induced hyperprolactinemia

Hyperprolactinemia is a pathological condition resulting from increased prolactin that directly affects reproduction, as this condition inhibits the release of LH, FSH and gonadal steroidogenesis, bringing several negative clinical associations in reproduction. In contrast, melatonin (MEL) plays an important role in the regulation of steroidogenesis and modulates damages to the process of spermatogenesis. The objective was to analyze the protective effects of exogenous melatonin on the testis of hyperprolactinemic adult rats. Forty-eight male rats were used, divided into two treatment periods: 30 and 60 days, each treatment was subdivided into three groups: Control, Hyper (hyperprolactinemia), and Hyper+MEL (hyperprolactinemia and melatonin). Treatment with melatonin was 200 μg/100 g, subcutaneously. Induction of hyperprolactinemia was obtained with a dose of 4 mg/kg of domperidone, subcutaneously. The results of the histopathology demonstrated that the animals in the Hyper group presented degeneration of germ cells when compared to the control. In addition, the degenerations were presented in smaller quantities in the Hyper+MEL, in both treatment periods, evidencing the benefits of the melatonin in gonadal regeneration. The Hyper group of both treatment periods showed a decrease in tubular diameter, epithelium height, and tubular area, in addition to a decrease in Sertoli cells, when compared to the control and the Hyper+MEL group. In conclusion, the hyperprolactinemia can affect the germinal epithelium and testicular microstructure; the exogenous melatonin has a protective effect against hyperprolactinemia, reducing testicular damage.     

Melatonin implantation during spring and summer does not affect the seasonal rhythm of feeding in anadromous Arctic charr (Salvelinus alpinus)

Plasma melatonin levels in the high-latitude teleost Arctic charr (Salvelinus alpinus) are constantly low during summer when feeding activity is high, and high during the dark winter when they eat little and loose weight. The question arises if melatonin is involved in the phase-setting of annual rhythms of feeding and growth and if low summer melatonin production is permissive for high summer growth in this species. The present study was therefore set out to compare the seasonal appetite and growth rhythms in Arctic charr with constantly high plasma melatonin levels from February throughout the Arctic summer (melatonin implanted, average mid-day plasma melatonin levels 1,106 ± 147 pg/ml) with those of fish with natural plasma melatonin levels (vehicle implanted and untreated fish with average mid-day plasma melatonin levels of 94 ± 13 and 58 ± 6 pg/ml, respectively). Feed intake, body mass or body length, as well as the timing of the seasonal growth rhythm, were not affected by the high summer plasma melatonin level. Further, Arctic charr fasted for 3 months had a 24 h plasma profile of melatonin which was consistently higher throughout the scotophase compared to fed charr. Although the daily melatonin production seems to be affected by the energy status of the fish, melatonin does not seem to be directly involved in regulation of the seasonal feeding and growth rhythm in the high-latitude, anadromous Arctic charr.     

Chronic Melatonin Administration Reduced Oxidative Damage and Cellular Senescence in the Hippocampus of a Mouse Model of Down Syndrome

Previous studies have demonstrated that melatonin administration improves spatial learning and memory and hippocampal long-term potentiation in the adult Ts65Dn (TS) mouse, a model of Down syndrome (DS). This functional benefit of melatonin was accompanied by protection from cholinergic neurodegeneration and the attenuation of several hippocampal neuromorphological alterations in TS mice. Because oxidative stress contributes to the progression of cognitive deficits and neurodegeneration in DS, this study evaluates the antioxidant effects of melatonin in the brains of TS mice. Melatonin was administered to TS and control mice from 6 to 12 months of age and its effects on the oxidative state and levels of cellular senescence were evaluated. Melatonin treatment induced antioxidant and antiaging effects in the hippocampus of adult TS mice. Although melatonin administration did not regulate the activities of the main antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase) in the cortex or hippocampus, melatonin decreased protein and lipid oxidative damage by reducing the thiobarbituric acid reactive substances (TBARS) and protein carbonyls (PC) levels in the TS hippocampus due to its ability to act as a free radical scavenger. Consistent with this reduction in oxidative stress, melatonin also decreased hippocampal senescence in TS animals by normalizing the density of senescence-associated β-galactosidase positive cells in the hippocampus. These results showed that this treatment attenuated the oxidative damage and cellular senescence in the brain of TS mice and support the use of melatonin as a potential therapeutic agent for age-related cognitive deficits and neurodegeneration in adults with DS.     

Melatonin reduces locomotor activity and circulating cortisol in goldfish

The present study focused on the effects of a subchronic melatonin treatment on locomotor activity and cortisol plasma levels in goldfish. We compared two different administration routes: peripheral (10 μg/g body weight) versus central (1 μg/μl) injections of melatonin for 7 or 4 days, respectively. Daily locomotor activity, including both diurnal and nocturnal activities, food anticipatory activity and circulating cortisol at 11:00 (under 24 h of food deprivation and 17 h postinjection) were significantly reduced after repeated intraperitoneal injections with melatonin for 7 days, but not after intracerebroventricular treatment. Taking in mind the anoretic effect of melatonin in this species, we investigated if such feeding reduction is directly responsible for the reduction in motor activity induced by melatonin treatment. Food restriction (50%) for 10 days did not significantly modify either daily locomotor activity or plasma cortisol levels in goldfish, indicating that the peripheral action of melatonin diminishing locomotor activity in goldfish is not a direct consequence of its anoretic action. In summary, our results indicate that, as previously described in other vertebrate species, melatonin can regulate locomotor activity and cortisol levels in goldfish, suggesting a sedative effect of this hormone in this teleost.     

Effectiveness of melatonin and controlled internal drug release device treatment on reproductive performance of buffalo heifers during out-of-breeding season under tropical conditions

Sixteen Murrah buffalo heifers, divided into control and treatment groups of eight animals each, were used to study the effect of melatonin and controlled internal drug release (CIDR) device treatment on the resumption of ovarian activity during out-of-breeding season (summer solstice). Treated group was implanted with melatonin (18 mg of melatonin per 50 kg of body weight) for 45 days and then heifers of both groups received CIDR for 9 days. All heifers received intramuscular 500 IU eCG on the day before CIDR removal and 10 μg GnRH on the day after CIDR withdrawal. All animals were subjected to estrus detection daily. Blood sampling in conjunction with transrectal ultrasonography were performed twice weekly to determine serum concentrations of melatonin, progesterone, LH, and antioxidant enzyme activities, as well as to monitor the ovarian follicular activity. Melatonin treatment resulted in an increase (P < 0.01) in serum melatonin and a decrease (P < 0.01) in serum progesterone and LH. In addition, melatonin had no significant effect on the frequency of LH pulses. Furthermore, melatonin treatment increased (P < 0.01) the diameter of the largest follicle and the number of large follicles between Days 0 and 35 of melatonin treatment. However, melatonin exhibited superior ability to maintain CL at 21 days after artificial insemenation (AI) and increased the percentage of conception to threefold higher than control. In conclusion, melatonin implantation successfully improved the diameter of largest follicles and the ability to maintain CL at 21 days after AI in buffalo heifers during out-of-breeding season under tropical conditions.     

Effect of a single subcutaneous injection of melatonin on estrous response and conception rate in goats

The objectives of this study were to evaluate the effect of a single subcutaneous injection of melatonin, on estrous induction and conception rate during the non-breeding season at different times of the year. In Experiment 1 the melatonin powder was dissolved in an oily vitamin A, D, E solution and injected subcutaneously randomly to goats in two dose treatment groups of 20 mg (MLT-20; n = 20) and 40 mg (MLT-40; n = 20) in January (winter). Twenty does were injected with 1 ml vitamin A and served as the control. In the MLT-20 treated goats 70% of the does were in estrus within 20.0 ± 2.0 days, whereas in the MLT-40 group 85% of the does were in estrus within 15.5 ± 2.5 days and 100% and 80% of the does, respectively, conceived on mating with the bucks. Only 10% of the untreated control does exhibited estrus, but none conceived. The breeding season was thus initiated earlier by 1–1.5 months in the treated goats. In Experiment 2, goats were treated with similar MLT-20 and MLT-40 treatments in May (spring), with 20 goats in each treatment group and 20 control goats. The proportion of goats that responded to the melatonin treatments was 80% and 90% in the MLT-20 and MLT-40 treatments, respectively, with no significant differences recorded regarding the estrous response. However, in the MLT-20 treatment group the estrous induction interval was significantly longer (P < 0.05), compared to the MLT-40 treatment. The pregnancy rates were not significantly different for the MLT-20 and MLT-40 treatments, with melatonin resulting in significantly higher pregnancy rates than in the control (88.4% versus 33.3%) and the breeding season initiated 2 months earlier. It could be concluded that a single subcutaneous injection of melatonin can initiate the breeding season (irrespective of the season of the year) earlier by 1–2 months in goats and this could be advantageous when using accelerated breeding systems.     

Effect of exogenous melatonin on viability, ingestion capacity, and free-radical scavenging in heterophils from young and old ringdoves (Streptopelia risoria)

The decrease of melatonin production with aging contributes to the decline in immune function as organisms age. Treatment with the exogenously administered indoleamine restores the reduced immunological functions. Therefore, we investigated the effect of melatonin on viability, phagocyte ingestion capacity, and free radical generation levels of heterophils from young and old ringdove (Streptopelia risoria) aged 3–4 and 11–13 years, respectively. Animals received a single oral dose of melatonin 1 h before lights off for three consecutive days. Experiments were performed at the acrophases and nadirs of melatonin. Melatonin treatment significantly increased serum melatonin levels at the acrophases, but not at the nadirs of the two age groups. In both young and old animals there was increased heterophil viability at acrophases with respect to nadirs, and also increased cell resistance to oxidative stress in the old animals after the melatonin treatment. At acrophases, the index, percentage and efficiency of phagocytosis all increased significantly, and superoxide anion levels decreased significantly with respect to the nadir values of vehicle and melatonin-treated animals, the effect being greater in young than in old ringdoves. At the nadirs, no change was observed in any parameter analyzed. In both young and old animals, phagocytosis and melatonin were positively correlated, while superoxide anion levels and melatonin were negatively correlated. In conclusion, exogenous melatonin enhanced heterophil viability in old animals as well as increasing phagocytosis and free-radical scavenging in both age groups during the nocturnal period, accompanied by an increase in the levels of the indoleamine.     

Modulation of immunity in young-adult and aged squirrel, Funambulus pennanti by melatonin and p-chlorophenylalanine

Background  

Our interest was to find out whether pineal gland and their by melatonin act as modulator of immunosenescence. Parachlorophenylalanine (PCPA) – a β adrenergic blocker, is known to perform chemical pinealectomy (Px) by suppressing indirectly the substrate 5-hydroxytryptamine (5-HT) for melatonin synthesis and thereby melatonin itself. The role of PCPA, alone and in combination with melatonin was recorded in immunomodulation and free radical load in spleen of young adult and aged seasonal breeder Indian palm squirrel Funambulus pennanti.     

Acutely administered melatonin reduces oxidative damage in lung and brain induced by hyperbaric oxygen

Pablos, Marta I., Russel J. Reiter, Jin-Ing Chuang, GenaroG. Ortiz, Juan M. Guerrero, Ewa Sewerynek, Maria T. Agapito, DanielaMelchiorri, Richard Lawrence, and Susan M. Deneke. Acutely administered melatonin reduces oxidative damage in lung and brain induced by hyperbaric oxygen. J. Appl.Physiol. 83(2): 354-358, 1997.Hyperbaric oxygenexposure rapidly induces lipid peroxidation and cellular damage in avariety of organs. In this study, we demonstrate that the exposure ofrats to 4 atmospheres of 100% oxygen for 90 min is associated withincreased levels of lipid peroxidation products [malonaldehyde(MDA) and 4-hydroxyalkenals (4-HDA)] and withchanges in the activities of two antioxidative enzymes[glutathione peroxidase (GPX) and glutathione reductase (GR)], as well as in the glutathione status in the lungs and in the brain. Products of lipid peroxidation increased after hyperbaric hyperoxia, both GPX and GR activities were decreased, and levels oftotal glutathione (reduced+oxidized) and glutathione disulfide (oxidized glutathione) increased in both lung and brain areas (cerebralcortex, hippocampus, hypothalamus, striatum, and cerebellum) but not inliver. When animals were injected with melatonin (10 mg/kg) immediatelybefore the 90-min hyperbaric oxygen exposure, all measurements ofoxidative damage were prevented and were similar to those in untreatedcontrol animals. Melatonin's actions may be related to a variety ofmechanisms, some of which remain to be identified, including itsability to directly scavenge free radicals and its induction ofantioxidative enzymes via specific melatonin receptors.

     

Pineal–adrenal–immune system relationship under thermal stress: effect on physiological,endocrine, and non-specific immune response in goats

The purpose of the investigation was to observe the pineal–adrenal–immune system relationships and their influence on non-specific immune response in female goats under short-term thermal stress. Six female goats had been exposed to 40°C and 60% relative humidity in the psychrometric chamber for 17 days. Blood samples were obtained on days 0 and 10 to establish control and thermal stress effects, respectively. Chemical adrenalectomy was achieved by injecting metyrapone (100 mg/kg body weight) followed by exogenous melatonin treatment (0.1 mg/kg body weight) from 11th to 17th day of experiment. Thermal stress significantly (P ≤ 0.05) altered the physiological responses. Metyrapone and melatonin treatment significantly (P ≤ 0.05) reduced the thermal-stress-induced increase in plasma concentrations of cortisol and corticosterone while significantly (P ≤ 0.05) increased the plasma melatonin on days 11 and 17. Furthermore, these treatments significantly (P < 0.05) increased the phagocytic activity of neutrophils as compared to both control and thermal exposure values from 11–17 days of experiment. The data generated from this study help us to understand the functional relationship between pineal, adrenal, and immune system, and how this relationship modifies the non-specific immune response for the well being of goats during thermal stress.     

Age-related telomere attrition in the human putamen

Age is a major risk factor for neurodegenerative diseases. Shortening of leucocyte telomeres with advancing age, arguably a measure of “biological” age, is a known phenomenon and epidemiologically correlated with age-related disease. The main mechanism of telomere shortening is cell division, rendering telomere length in post-mitotic cells presumably stable. Longitudinal measurement of human brain telomere length is not feasible, and cross-sectional cortical brain samples so far indicated no attrition with age. Hence, age-related changes in telomere length in the brain and the association between telomere length and neurodegenerative diseases remain unknown. Here, we demonstrate that mean telomere length in the putamen, a part of the basal ganglia, physiologically shortens with age, like leukocyte telomeres. This was achieved by using matched brain and leukocyte-rich spleen samples from 98 post-mortem healthy human donors. Using spleen telomeres as a reference, we further found that mean telomere length was brain region-specific, as telomeres in the putamen were significantly shorter than in the cerebellum. Expression analyses of genes involved in telomere length regulation and oxidative phosphorylation revealed that both region- and age-dependent expression pattern corresponded with region-dependent telomere length dynamics. Collectively, our results indicate that mean telomere length in the human putamen physiologically shortens with advancing age and that both local and temporal gene expression dynamics correlate with this, pointing at a potential mechanism for the selective, age-related vulnerability of the nigro-striatal network.     

Melatonin Ameliorates Cerebral Vasospasm After Experimental Subarachnoidal Haemorrhage Correcting Imbalance of Nitric Oxide Levels in Rats

In the present study, we investigated the in vivo effects of melatonin on SAH-induced cerebral vasospasm and oxidative stress, resulting from SAH in an experimental rat model. Twenty-eight rats (225–250 g) were divided into four groups equally: group 1; control, group 2; SAH, group 3; SAH plus placebo, and group 4; SAH plus melatonin. We used double haemorrhage method for SAH groups. Beginning 6 h after SAH, 20 mg/kg melatonin or equal volume of 0.9% saline was administered intraperitoneally twice daily for 5 days to groups 3 and 4, respectively. Melatonin or 0.9% saline injections were continued up to fifth day after SAH and rats were sacrificed at the end of this period. Brain sections at the level of the pons were examined by light microscopy. The lumen diameter and the vessel wall thickness of basilar artery were measured using a micrometer. The serum levels of cerebral vasodilator nitric oxide (NO), the brain levels of an intrinsic antioxidant superoxide dismutase (SOD) and a NO regulator arginase activities were measured. The brain levels of inducible nitric oxide (iNOS) and nitrotyrosine, a nitrosative stress parameter immunohistochemiacally determined. In conclusion, melatonin administration ameliorated cerebral vasospasm by increasing serum NO level and decreasing the brain the levels of arginase and oxidative stress. It is therefore possible that increased brain arginase activity after SAH may also have a significant role in the pathogenesis of vasospasm by limiting the availability of arginine for NO production.