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Pinealocyte

About: Pinealocyte is a research topic. Over the lifetime, 1605 publications have been published within this topic receiving 55609 citations.


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Book ChapterDOI
01 Jan 1992
TL;DR: Rhythms with a periodicity of 24 h (daily) or one year (annual) represent major components in the adaptation of organisms to their environment and environmental factors play an important role in the synchronization of these rhythms.
Abstract: Many, if not most, biochemical, physiological and behavioural events are rhythmic. Rhythms with a periodicity of 24 h (daily) or one year (annual) represent major components in the adaptation of organisms to their environment. Environmental factors, such as light and temperature, play an important role in the synchronization of these rhythms. In vertebrates, synchronization is mediated through the circadian system, which is composed of sensors and circadian oscillators. These include the pineal organ, the lateral eyes and the suprachiasmatic nuclei of the hypothalamus.

92 citations

Journal ArticleDOI
TL;DR: The pineal gland, via the rhythmical synthesis and release of melatonin, influences the development and function of the immune system, although the postreceptor signal transduction system is poorly understood.
Abstract: The pineal gland is a vertebrate neuroendocrine organ converting environmental photoperiodic information into a biochemical message (melatonin) that subsequently regulates the activity of numerous target tissues after its release into the bloodstream. A phylogenetically conserved feature is increased melatonin synthesis during darkness, even though there are differences between mammals and birds in the regulation of rhythmic pinealocyte function. Membrane-bound melatonin receptors are found in many peripheral organs, including lymphoid glands and immune cells, from which melatonin receptor genes have been characterized and cloned. The expression of melatonin receptor genes within the immune system shows species and organ specificity. The pineal gland, via the rhythmical synthesis and release of melatonin, influences the development and function of the immune system, although the postreceptor signal transduction system is poorly understood. Circulating messages produced by activated immune cells are reciprocally perceived by the pineal gland and provide feedback for the regulation of pineal function. The pineal gland and the immune system are, therefore, reciprocally linked by bidirectional communication.

91 citations

Journal ArticleDOI
TL;DR: Opsin-like immunoreactivity was observed in the retinae and pineal organs of the mouse, rat and guinea pig, and the pineal organ of the cat.
Abstract: Opsin-like immunoreactivity was observed in the retinae and pineal organs of the mouse, rat and guinea pig, and the pineal organ of the cat. In the retina the immunoreaction was restricted to photoreceptor cells, which displayed immunostaining in their perikarya and outer and inner segments. Distinct pinealocytes endowed with characteristic processes were labelled in the pineal organs of the mouse and cat. However, in the cat the number of immunoreactive pinealocytes was very limited. In the pineal organs of the rat and guinea pig immunoreaction was very weak and diffuse. No immunoreaction was observed when the antibody was preabsorbed with purified bovine (rhod)opsin. These findings are in accord with the results of previous studies indicating molecular similarities between retinal photoreceptors and pinealocytes in mammals.

91 citations

Journal ArticleDOI
TL;DR: Although melatonin administration has been reported to inhibit blood T4 levels in both rats and hamsters, under certain experimental conditionsmelatonin administration can be demonstrated to have a counter-antithyrotrophic effect resulting in increased blood levels of T4 and thyrotrophin.
Abstract: Experiments with rats and hamsters have provided evidence for an inhibitory action of the pineal gland on the neuroendocrine-thyroid axis. While maintenance of these animals in short photoperiod results in reduced levels of circulating thyroxin (T4), pinealectomy restores the levels to normal. Recent studies suggest that an active pineal gland produces a substance which inhibits thyrotrophin-releasing hormone release from the hypothalamus. Several investigators have concluded that endogenous melatonin, produced in the pineal gland, could account for the inhibitory action of the pineal gland on blood T4 levels. Although melatonin administration has been reported to inhibit blood T4 levels in both rats and hamsters, under certain experimental conditions melatonin administration can be demonstrated to have a counter-antithyrotrophic effect resulting in increased blood levels of T4 and thyrotrophin. Assay of blood levels of melatonin of rats and hamsters under various experimental conditions will be necessary to distinguish physiological from pharmacological effects of melatonin. Lesion studies as well as studies with melatonin implants in the brain, suggest that the site of action is in the anterior hypothalamus. The effects of melatonin on the neuroendocrine-thyroid axis are similar to its effects on the neuroendocrine-gonadal axis, leading to the hypothesis of a common site of action for the thyroid and gonadal effects of melatonin. Although many pineal 'factors' have been postulated to account for the action of this gland, an action of melatonin on the serotonergic system of the brain stem could account for the data.

91 citations

Journal ArticleDOI
TL;DR: The results of this study imply that the SCN can influence the sympathetic outflow of the hypothalamus through its GABA-containing projection, which probably explain the previously reported strong inhibitory effect of benzodiazepines on plasma melatonin in both animals and humans.
Abstract: Recently, anatomical evidence was presented that the mammalian circadian clock located in the suprachiasmatic nuclei (SCN) may utilize GABA to transmit diurnal information to the dorsomedial hypothalamus (DMH). The present study provides further physiological evidence for the involvement of this GABAergic projection in the regulation of diurnal rhythms. Infusion of the GABA agonist muscimol in the region of the DMH completely blocked the daily increase of plasma melatonin during darkness and reduced sympathetic output in the pineal gland resulting in lower pineal melatonin production, as measured with transpineal microdialysis. Further experiments in SCN-lesioned animals indicated that the origin of this inhibitory input to the DMH is indeed the SCN. The results of this study imply that the SCN can influence the sympathetic outflow of the hypothalamus through its GABA-containing projection. Furthermore, the present results probably explain the previously reported strong inhibitory effect of benzodiazepines on plasma melatonin in both animals and humans.

90 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202310
202219
202116
202011
201915
201817