摘要:

Abstract:The effect of melatonin as well as pinealectomy on the basal and K+‐evoked release of vasopressin and oxytocin from the neurointermediate lobes in vitro was determined. Pineal removal resulted in a diminution of vasopressin and oxytocin release from the neurointermediate lobes in vitro. Melatonin (10−3or 10−6M/1) increased vasopressin and oxytocin release from neurointermediate lobes of sham‐operated rats. Nevertheless, when pinealectomized rats served as donors of the neurointermediate lobes, melatonin (10−3or 10−6M/1) increased vasopressin release under basal conditions. For the same tissue, melatonin did not affect the oxytocin release either under basal conditions or during depolarization due to excess potassium. When 10−7M/l melatonin was used, no changes in either vasopressin or oxytocin release were obse

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00019.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:In order to investigate the effect of food deprivation on the levels of indoles in the brain and the gastrointestinal tissues, we have determined tissue levels of tryptophan (TRP), serotonin (5‐HT), 5‐hydroxyindoleacetic acid (5‐H1AA), and melatonin in the brain and the gastrointestinal tract (GIT) of mice on ad libitum diet as well as in mice deprived of food for 24 and 48 hr. The reduction of food intake 1) had no effect on TRP levels in the brain, but increased TRP concentrations in the stomach and the gut, especially in the colon; 2) decreased 5‐HT levels in the brain, but increased values in the stomach and the intestines; 3) decreased 5‐HIAA levels in the brain, but increased them in the stomach and the intestines; 4) did not change 5‐HT conversion to 5‐HIAA in the brain, stomach, and the jejunum, but increased the conversion in the ileum and colon and; 5) increased melatonin levels in all tissues investigated, particularly in the stomach and the brain. The changes of indole levels induced by food deprivation were compared to their known function in the brain and the individual segments of the GIT. A possible serotonin‐melatonin antagonism in the brain and GIT functio

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00020.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:Protein kinase C and its family of multiple subspecies play pivotal roles in cell‐surface mediated signal transduction. For example, in the process of synthesizing melatonin, the activation of α1‐adrenergic receptor sites in the pineal gland causes translocation of protein kinase C, which in turn enhances the β‐adrenergic‐activated accumulation of both cyclic AMP and cyclic GMP. In the retina, protein kinase C phosphorylates rhodopsin and hence is involved in visual transduction. The activation of protein kinase C depends on the presence of phospholipid and Ca++. In this communication, we report that the bovine pineal gland and retina possess unique protein kinase C isoenzymes that are distinct from those seen in the rat brain. Furthermore, in retinoblastoma cells in culture, protein kinase C is stimulated by a cooperative interaction between calcium and zinc. Moreover, the subcellular regions of retina that exhibit the highest activity of protein kinase C also possess the highest concentration of zinc. In view of the fact that the bovine pineal gland and retina continually synthesize metallothionein and other low molecular weight zinc binding proteins, we propose that zinc and metallothionein participate in signal transduction in the retina and pineal gland. The action of metallothionein, a zinc binding protein, in activating protein kinase C is opposite to that of calcium binding protein, which is a potent inhibitor of protein

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00021.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The effect of daily injections of the pineal hormone melatonin and naltrexone, an opioid antagonist, on the circadian rhythm and the level of immune parameters (plaque forming cell [PFC] number, serum agglutinin titer, lymphoid gland weight, total white blood cells (WBC) and their fraction number, and serum lysozyme [LZ]content) was examined in White Leghorn cockerels and female BALB/c mice kept in LD 12:12. Animals were immunized ip with sheep red blood cells (SRBC) to stimulate their immune system. Subcutaneous injections of melatonin, naltrexone, or both drugs together were made 2 hr before the end of light, for 4 or 5 days, beginning on the day of immunization. The day following the fifth injection, chickens were sacrificed over a 24 hr period every 4 hr (experiment I) or twice daily, i.e., at the beginning of light and dark phases (experiment II). Mice were killed on the day following the fourth injection at the beginning of light, and splenic PFC number was determined (experiment III). In experiment I, the existence of the diurnal rhythm was evaluated by cosinor analysis. Melatonin injections entrained the circadian rhythm in anti‐SRBC serum agglutinins, but it did not influence circadian rhythmicity in other parameters examined. The circadian rhythm in total WBC number and their fractions was entrained by naltrexone treatment. Melatonin injections did not affect either the diurnal mean of parameters examined or the weight of lymphoid organs. Splenic PFC number in chickens was diminished by both melatonin and naltrexone injections, whereas in mice it was increased by melatonin, and naltrexone antagonized that effect. It is concluded that melatonin in chickens, at least in the dose range used, is not an immunoenhancing agent, as in mice. Possible reasons for this difference are discusse

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00022.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The purpose of this study was to compare the responses of the Syrian hamster and rat pineal glands in organ culture to vasoactive intestinal peptide (VIP). The endpoints in these studies were the activities of pineal N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT), as well as pineal and medium melatonin levels. When rat pineal glands were incubated with either VIP (1 μM) or isoproterenol (1 μM), a β‐adrenergic agonist, a significant increase in NAT and HIOMT activities and melatonin levels were observed within 3 hr. Conversely, during the day, VIP (1 μM) was ineffective in stimulating these parameters in hamster pineal gland after incubation times of either 2, 4, 6, or 8 hr. In another experiment, hamster pineal glands were collected from animals killed in the late dark period (after 30 min light exposure). In these glands, isoproterenol promoted NAT activity and melatonin production; however, VIP was ineffective in stimulating either NAT or HIOMT activities; likewise, VIP had no stimulatory effect on pineal melatonin levels at night. Finally, when hamster pineal glands at night were incubated with either 0, 10 nM, 100 nM, 10 μM, or 100 μM VIP, no changes in any parameter of melatonin synthesis were measured. The results indicate that the hamster pineal gland, unlike that of the rat, may not respond to VIP with an increased melaton

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00023.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:Alpha‐methyltryptophan (AMTP), a synthetic amino acid, is metabolized by the rat in vivo to alpha‐methylserotonin (AM5HT), which appears in the pineal gland just as it does in the brain. Pineal AM5HT assumes the same diurnal rhythm as serotonin does in control animals. Administration of AMTP results in a decrease of the serotonin content of the pineal gland, but not of its melatonin content. Pharmacological evidence indicates that the uptake of AMTP into the gland is influenced by noradrenergic innervation. No evidence was obtained for formation in vivo of alpha‐methyl‐N‐acetylserotonin or the alpha‐methyl analogue o

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00024.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The suppression of melatonin by bright light is probably mediated by the suprachiasmatic nucleus (SCN) in humans. In animals, SCN cells have broad visual receptive fields, suggesting that peripheral bright light could be effective for melatonin suppression. Twelve healthy subjects were subjected to 1000 lux illumination for 2 hr from 0100 to 0300 on two occasions: once lighting the central visual field 5° from the center of gaze and once lighting the peripheral visual field 60° lateral to the direction of gaze. Six subjects were observed on a third occasion in dim light. The three conditions differed significantly, with less melatonin secreted in 1000 lux, but melatonin levels with central and peripheral illumination did not differ. This suggests that phototherapy using bright light in the visual periphery may be effectiv

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00025.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY