摘要:

This study examined whether melatonin‐induced inhibition of testicular weight and body weight in vivo could be antagonized by luzindole, a competitive melatonin receptor antagonist, or methysergide, a competitive serotonin receptor antagonist. Adult male Siberian hamsters were exposed to a long photoperiod (16L:8D) and given daily injections of drugs 3 h before lights off for 7 weeks. Hamsters treated with melatonin (0.375 mg/kg) exhibited testicular regression and loss of body weight. These effects were also marked in hamsters treated concommitantly with melatonin (0.375 mg/kg) and luzindole (10 mg/kg). In other studies, chronic injections of luzindole (30 mg/kg) to juvenile hamster failed to antagonize testicular regression induced by either melatonin injections or exposure to a short day photoperiod (12L: 12D). In contrast, concommitant injections of methysergide (6.25 mg/kg) and melatonin attenuated testicular regression and loss of body weight. When administered alone, neither luzindole nor methysergide affected testicular weight or body weight, whereas chronic injections of 5‐methyoxyluzindole (10 mg/kg) mimicked the inhibitory effects of melatonin. 5‐Methoxyluzindole inhibits 2‐[125I]‐iodomelatonin binding to median eminence/pars tuberalis membranes with an affinity similar to that of melatonin. Luzindole shows lower affinity for the inhibition of 2‐[125I]‐iodomelatonin binding than melatonin, which may explain why luzindole is not an effective melatonin receptor antagonist when administeredin vivo. Methysergide, which has a very low affinity for inhibition of 2‐[125I]‐iodomelatonin binding, probably inhibits the effects of melatonin by blocking serotonergic

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00898.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effects of some general purpose drugs on the deactivation and activity measurement of the chicken pineal gland enzyme serotonin N‐acetyl transferase (EC 2. 3. 1. 5.) were studied. The drugs used were EGTA and two neutral surfactants, Nonidet P40 and Triton X‐100. Enzyme activity showed significant variations ranging from 2.8 ± 1.3 nmol/gland/h when Nonidet P40 was added to the homogenate buffer, to 31.8 ± 1.7 nmol/gland/h when EGTA was present. This striking variation seemed to be caused by the ability of these compounds to modify the rate of NAT deactivation acting either as accelerating agents, as in the case of the detergents or as braking agent, as in the case of

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00899.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The aim of this study was to investigate the ultrastructure of rat pinealocyte during daytime (1600 h) and at night (0100 h) and to compare these observations with serum melatonin levels in the same animals. In addition, pineal melatonin concentrations were determined in other animals. Both serum and pineal melatonin concentrations were significantly higher at night than during daytime (34 and 21 times, respectively). Sizes of pinealocytes, their nuclei, and nucleoli, as well as cross‐sectional areas of mitochondria and granular endoplasmic reticulum were also higher at night than during daytime, whereas areas of lysosomes, Golgi apparatus, and vacuoles containing flocculent material did not differ at the time points studied. In contrast, the number of dense‐core vesicles was higher during daytime. The results of the present study show that morphological patterns of higher metabolic activity of the rat pinealocyte at night when compared to those during daytime correlate with melatonin concentrati

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00900.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A study was carried out to determine possible effects of 60‐Hz electromagnetic‐field exposure on pineal gland function in humans. Overnight excretion of urinary 6‐hydroxymelatonin sulfate (6‐OHMS), a stable urinary metabolite of the pineal hormone melatonin, was used to assess pineal gland function in 42 volunteers who used standard (conventional) or modified continuous polymer wire (CPW) electric blankets for approximately 8 weeks. Volunteers using conventional electric blankets showed no variations in 6‐OHMS excretion as either a group or individuals during the study period. Serving as their own controls, 7 of 28 volunteers using the CPW blankets showed statistically significant changes in their mean nighttime 6‐OHMS excretion. The CPW blankets switched on and off approximately twice as often when in service and produced magnetic fields that were 50% stronger than those from the conventional electric blankets. On the basis of these findings, we hypothesize that periodic exposure to pulsed DC or extremely low frequency electric or magnetic fields of sufficient intensity and duration can affect pineal gland function in certain

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00901.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

After chronic administration of epithalamin (a pineal peptide drug), an increase in the amplitude and shifts in the acrophase of rat's circadian locomotor activity to late hours were observed. These results were obtained only in rats with low initial amplitude of their circadian rhythm. Epithalamin also changed the time‐course of forced swimming and decreased the rhythmic index of depression. These observations suggest that the pineal gland of the rat, via its peptides, may prevent the development of depressive‐like eve

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00902.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY