The possible interaction of melatonin receptors and D1 dopamine receptors was investigated in neural cells prepared from embryonic day 8 chick retinas and cultured for 6 d. Dopamine stimulated cAMP accumulation in cultured retinal cells. This effect of dopamine was antagonized by addition of dopamine receptor antagonists (haloperidol and SCH23390) or melatonin receptor agonists (melatonin, 2-io...

Melatonin (N-acetyl-5-methoxytryptamine) is an indolamine hormone produced by the pineal gland that works to regulate sleep/wake cycles and activity rhythms. The effects of melatonin in metabolism are far from understood. Melatonin was injected into the fiddler crab, Uea pugilator, to investigate the effects of melatonin on hemolymph glucose and lactate levels. Following injection at t=O, hemol...

To identify the characteristics of the oscillator located in the pineal organ, we examined the effects of temperature and light on melatonin secretion rhythm using pineal organs in cultures. At 20 degrees C, the melatonin rhythm was obvious: low secretion during the daytime and high during the nighttime. When the temperature was lowered from 20 to 10 degrees C, the melatonin rhythm disappeared....

Background. Sleep disturbances and cognitive dysfunction are common in patients with breast cancer. Disturbed sleep leads to poor cognitive performance and exogenous melatonin may improve sleep and attenuate cognitive dysfunction. We hypothesized that melatonin would improve sleep and cognitive function after surgery. Methods. This study reports secondary endpoints from a randomized, double-bli...

The human skin is not only a target for the protective actions of melatonin, but also a site of melatonin synthesis and metabolism, suggesting an important role for a local melatoninergic system in protection against ultraviolet radiation (UVR) induced damages. While melatonin exerts many effects on cell physiology and tissue homeostasis via membrane bound melatonin receptors, the strong protec...

In this paper evidence that supports a new role for melatonin as a negative endogenous regulator of cytosolic phospholipase A(2) (cPLA(2)) is presented. When rat pineal glands were incubated in culture, time-dependent release of arachidonic acid (AA) was observed, which was significantly inhibited by a known 85-kDa cPLA(2) inhibitor, methyl arachidonyl fluorophosphonate. Co-incubation with mela...

N-acetyl-5-methoxytryptamine (Melatonin), as a crucial messenger in plants, functions in adjusting biological rhythms, stress tolerance, plant growth and development. Several studies have shown the retardation effect of exogenous melatonin treatment on plant growth and development. However, the in vivo role of melatonin in regulating plant leaf growth and the underlying mechanism are still uncl...

Aging alters many aspects of circadian rhythmicity, including responsivity to phase-shifting stimuli and the amplitude of the rhythm of melatonin secretion. As melatonin is both an output from and an input to the circadian clock, we hypothesized that the decreased melatonin levels exhibited by old hamsters may adversely impact the circadian system as a whole. We enhanced the diurnal rhythm of m...

BACKGROUND/AIMS Small intestinal neuroendocrine tumours (SI-NETs) are derived from enterochromaffin cells. After demonstrating melatonin in enterochromaffin cells, we hypothesized that SI-NETs may express and secrete melatonin, which may have an impact on clinical factors and treatment response. METHODS Tumour tissue from 26 patients with SI-NETs, representing paired sections of primary tumou...

Melatonin has been reported to suppress adrenocorticotropin (ACTH) secretion in the anterior pituitary and cortisol production in the adrenal by different mechanisms. However, the effect of melatonin on aldosterone production has remained unknown. In this study, we investigated the role of melatonin in the regulation of aldosterone production using human adrenocortical H295R cells by focusing o...