摘要:

Melatonin injected in a single intraperitoneal dose of 100 μg/100 g b. w. to euhydrated rats resulted in a decrease of neurohypophysial oxytocin content but the hypothalamic oxytocin storage as well as the hypothalamo‐neurohypophysial storage of vasopressin were not changed. Following 8 d of once‐daily melatonin treatment the hypothalamic and neurohypophysial oxytocin and vasopressin content was decreased. It might be therefore suggested that melatonin increases the release of neurohypophysial hormones and/or decreases their synthesis.Melatonin did not significantly modify the neurohypophysial vasopressin depletion rate in animals deprived of water up to 8 days. No consistent effects of melatonin on the decrease of hypothalamo‐neurohypophysial content of oxytocin were noted under conditions of dehydration and simultaneous administration of melatonin up

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00743.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The spontaneous activity of 117 pineal units was recorded in urethane‐anesthetized rats. The pineal units exhibited a wide range of firing rates of which 50% were on average slower than 14 spikes per second. Superior cervical ganglion (SCG) stimulation was studied in 76 pineal units; this stimulation caused excitation in 55% of the units. Microiontophoretic application of norepinephrine (NE) induced changes of firing rates in 61% of the pineal units tested. Two patterns of activity following NE microiontophoresis was observed: increase in firing rate (64%) and decrease in firing rate (36%). NE‐induced excitation was observed only in those units excited by SCG stimulation. When NE and SCG stimulation were applied together, partial summation of the excitation induced by each one alone was observed. None of the units in which NE depressed the firing rate responded to SCG stimulation. Local application of propranolol blocked the excitation initiated by SCG stimulation as well as the excitation and the depression induced by NE microiontophore

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00744.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The presence of a high concentration of glutamic acid, a transmitter shown to have excitatory action in the pineal organ, prompted us to search for and to characterize glutamate receptor site in the bovine pineal organ. By using 10 nM‐100 μM of labeled and unlabeled L‐glutamate and by employing the LIGAND computer program, we found a glutamate binding site with a dissociation equilibrium constant (KD) of 0.534 μM and a receptor density (Bmax) of 4.84 pmol/mg protein. This pH‐ and temperature‐dependent binding site showed stereospecificity, was activated by Ca2+, and displayed affinity for both glutamate agonists and antagonists. The IC50values for L‐glutamate, L‐asparate, L‐cysteate, L‐cysteine sulfinate, quisqualate, and (±) ibotenate were 0.5, 2, 12, 16, 25, and 30 μM, respectively, whereas those for D‐aspartate, L‐α‐aminoadipate, L‐homocysteate, and DL(±) 2‐amino‐4‐phosphonobutyrate were greater than 100 μM. Kainate, N‐methyl‐D‐aspartate, and L‐glutamic acid diethyl ester were inactive. Based on these results, the presence of a quisqualate‐type, Cl−/Ca2+‐dependent glutamate binding site in the pineal organ is suggested, and a possible neuroexcitatory role for glutamic acid, aspartic acid, and certain sulfur‐containing amino acids is also implied. The precise nature of this excitatory effect in modulating the function(s) of the pineal organ and the syn

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00745.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Norepinephrine (NE, 10−6M) stimulated melatonin accumulation in the incubation medium of rat (but not Syrian hamster) pineals taken at the end of the light phase. However, NE elevated melatonin accumulation in the medium of pineals taken after 20 min of light exposure of animals of either species at 6 h into the 10‐h dark phase. A dose response to 10−7−10−5M NE was observed in both the medium and pineals upon incubation of pineals taken from rats at 4 h into the light phase and from hamsters after 20 min light exposure at 6 h into the dark phase. Approximately 95% of the melatonin present was in the medium. The incubation time was 4 h in all cases. Subcutaneous injection of 1 μg/g NE (either at the end of the light phase or after 30 min of light at 6 h into the dark phase) did not stimulate in vivo Syrian hamster pineal melatonin content determined 1 or 2 h after injection, whether the hamsters were placed in light or darkness after the injection. However, after 30 min of light beginning at 6 h into dark, injection of 5 μg/g desipramine (DMI, a blocker of catecholamine uptake into nerve endings) allowed a dramatic hamster pineal melatonin response to additional injection of 1 μg/g NE, observed at 1 and 2 h in light after injection. A small effect of DMI alone was seen. DMI also potentiated the effect of NE (each 10−6M) on melatonin accumulation in the medium of incubated hamster pineals taken after a short light exposure at night. No significant stimulatory effect of NE and/ or DMI was seen in vivo or in vitro near the middle of the light phase. Measurement of melatonin in the incubation medium is a useful method for studying pineal function. The Syrian hamster pineal has rhythm of sensitivity to NE (sensitivity evident at night) and even at night is protected by neuronal uptake from circulating NE‐induced stimulation of melatonin production. NE appears to be the neurotransmitter for stimulation of pineal melatonin production in the Syrian hamster. The sensitivity rhythm and uptake protection might provide specificity of control of the nightly melatonin signal by reducing the chance of a melatonin response during the day or a response to circulating catecholamines from general sym

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00746.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The serum concentration of melatonin, serotonin, and N‐acetylserotonin were measured by RIA procedures in 28 infants aged 1 week to 9 months. Blood specimens were obtained at 1200 hr and 2400 hr. A day‐night difference in serum serotonin was present immediately after birth. A significant (P<0.001) decrease in serum serotonin concentrations at 1200 hr and 2400 hr was observed from the first month of age to the third to ninth month of age. A significant (P<0.05) difference in day‐night N‐acteylserotonin concentration is first seen at age 1–3 months. Serum melatonin concentrations, though detectable, did not show any day‐night difference at birth. Melatonin concentrations progressively increased up to the third month of age, and a significant (P<0.01) day‐night difference appeared thereafter. The results indicate that in humans the circadian organizatijon for serotonin already exists at birth, and the circadian melatonin rhythm develop

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00747.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Intracranial injections of 10 μg melatonin, with or without 4 μg naloxone, result in reduced aggressive responsiveness by the cichlid fishAequidens pulcherto a mirror presented 20 min later. Naloxone, when administered on its own, had no behavioral effect. Intracranial injections of 25 μg serotonin‐creatinine sulphate complex (5HT‐CS) also reduced aggression. 5HT‐CS's action was abolished if the injection included 10 μg S‐adenosyl homocysteine (SAH), which inhibits the conversion of serotonin to melatonin. This suggests that the behavioral action of 5HT‐CS may be mediated by its conversion to melatonin. There is inconclusive evidence to suggest that 37.5 μg 5HT‐CS, administered in conjunction with 10 μg SAH, may reduce aggressiveness; injection of 50 μg 5HT‐CS, with or without 10 μg SAH, induced a pronounced escape behavior which precluded any measurement of aggre

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00748.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Results are given of daily excretion levels of 6‐oxymelatonin, thymic serum factor (FTS), and cortisol in the blood of 140 healthy subjects and 90 patients with skin melanoma, ranging from 20 to 49 years of age. Correlation factor (η) was used for evaluating the correlation between the indices examined. Daily excretion of 6‐oxymelatonin was found to decrease considerably in healthy men over 30 years of age, the extent of such reduction correlating with age (η= 0.48 ± 0.19,P<0.02). Similar correlation is absent in healthy women. There is an age‐related reduction in FTS in both healthy women (η= 0.63 ± 0.13,P<0.001) and men (η= 0.57 ± 0.12P<0.001), although in the latter this reduction occurs 10 years earlier (beginning at 30 years) and is more pronounced. Blood cortisol levels in healthy subjects increase with age, more notably in men than in women. Agerelated changes in the content of the hormones under study are still more pronounced when patients of corresponding age groups develop neoplasms. Male patients from 20 to 29 and 30 to 49 years of age with melanoma show daily levels of 6‐oxymelatonin excretion of 10.13 ± 0.71 μg/24 hr and 11.70 ± 1.26 μg/24 hr, respectively, while healthy men of the same age show much higher melatonin levels, i. e., 18.98 ± 1.36 μg/24 hr and 15.46 ± 1.13 μg/24 hr, respectively. Male melanoma patients aged 30 to 49 years have reduced log2of FTS titers (as little as 1.44 ± 0.23) compared to that of healthy, age‐matched males (3.40 ± 0.23,P<0.05). In female patients aged 20–39 years and 40–49 years, the log2of FTS titers was 1.96 ± 0.37 and 1.62 ± 0.25, respectively, which is significantly lower (P<0.05) than values for healthy women of the same age (5.60 ± 0.17 and 3.60 ± 0.41). In melanoma male and female patients from 20 to 49 years of age, cortisol levels are significantly higher than the mean values for this hormone in agematched healthy subjects, being 193.18 ± 19.67 ng/ml and 135.43 ± 14.36 ng/ml, respectively (with normal levels of 140.60 ± 9.62 ng/ml and 101.03 ± 8.61 ng/ml). The results of correlation analysis indicate that daily excretion values for 6‐oxymelatonin in healthy subjects correlate with both FTS titers and cortisol content, while the latter two correlate with each other (P<0.05). Statistically significant correlation between the levels of all examined hormones was fou

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00749.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Segments from various locations of the small and large intestine of the rat were removed, bathed in Tyrode's solution and attached to a force displacement transducer. Melatonin, while not influencing the frequency of contraction, did reduce the force of spontaneous contractions of duodenal and colon segments of rat intestine by 92 and 52%, respectively compared to only 25 and 22% for the ileum and jejunum, respectively. Areas with greatest responsiveness to melatonin were those that previous studies have shown to contain the largest concentrations of endogenous melatonin. Cyclic guanosine monophosphate, when tested in similar preparations, did not produce an inhibitory response characteristic of melatonin. It is hypothesized, therefore, that this hormone has physiological action within the gut, including motility; however, its action may not be directly on smooth muscle contraction but may be through an indirect action inhibiting the contractile response of serotonin, as suggested by other investigators.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00750.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The goal of the present investigation has been to compare the effect of melatonin on the early secretory event in the thyroid follicular cells (thyroglobulin endocytosis; colloid droplet [CD] formation) and the effect of this pineal indoleamine on the release of a stable prostacyclin (PGI2) metabolite, 6‐keto‐PGF1αfrom the thyroid. 6‐keto‐PGF1αis believed to be a good index of PGI2synthesis, since PGI2is not stored within the tissue, but is continuously formed and released. We found that melatonin, administered to rats as daily subcutaneous injections at a dose of 25 μg and/or 250 μg for a total of 3 days, inhibited the CD formation. Moreover, melatonin partially suppressed the stimulatory effect of TSH on the CD formation. In turn, melatonin did not affect 6‐keto‐PGF1αrelease in basal conditions, but blocked the stimulatory effect of TSH.It is concluded that melatonin decreases the thyroid secretion acting by a mechanism that is independent of the effect of this hormone on

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00751.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The aim of the present study has been to examine the effect of melatonin, administered to mice as daily subcutaneous injections for a total of 10 days, on the mitotic activity of thyroid follicular cells (TFC). The colchicine metaphasearrest technique was employed in the experiment. We found that melatonin (10μg and/or 100μg injection) decreased significantly the mean mitotic activity rate (MMAR) of TFC in both male and female mice. Moreover, melatonin totally suppressed the stimulatory effect of TSH on the MMAR of TFC in both sexes of mice.Furthermore, the effect of melatonin (5 × 10−7M) on the proliferation of TFC in the organ‐cultured rat and mouse thyroid explants was investigated. It was found that melatonin almost totally suppressed the MMAR of TFC in organ culture. Moreover, melatonin blocked the stimulatory effect of TSH on the MMAR of TFC in both rat and mouse thyroid explants. N‐acetylserotonin (NAc‐5HT, 10−6M) also decreased the MMAR of cultured thyroid explants, but its effect was less expressed when compared to melatonin inhibition.The present data indicate that melatonin can exert its inhibitory effect on the proliferation of TFC directly at the thyroid level, since this pineal indoleamine has been shown to suppress not only basal but also TSH‐stimulated mitotic activity.The results are in agreement with the hypothesis of a pineal‐thyroid negative feedback, assuming the direct inhibitory effect of melatonin on th

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1986.tb00752.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY