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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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Journal ArticleDOI
TL;DR: The results together with the available literature show that NPY is a sympathetic transmitter, and its actions in the pineal gland are, therefore, associated with the well‐documented roles of noradrenaline.
Abstract: The present review describes the anatomy of the neuropeptide (NPY)ergic innervation of the mammalian pineal gland with emphasis on the rat. The proNPY-molecule is post-translationally processed by a single cleavage to neuropeptide Y (NPY) and a C-terminal peptide of NPY (CPON). NPY is C-terminally amidated, and the amidation is essential for binding of NPY to its corresponding receptor(s). Since no proNPY has been detected in rat pineal extracts, it is considered that proNPY is immediately processed to its final products in the gland. In the rat, numerous NPY- and CPON-immunoreactive (ir) nerve fibers are present in the capsule of the superficial pineal gland and in the pineal parenchyma, mostly related to the connective tissue spaces and the vasculature of the gland, but also present between the pinealocytes. Furthermore, a substantial number of fibers was observed in the deep pineal gland, the pineal stalk, and the underlying epithalamus. Occasionally, NPY- or CPON-immunoreactive fibers were found adjacent to the stria medullaris and in the posterior commissure, which could be followed to the adjacent deep pineal gland. At the ultrastructural level, the NPY-immunoreactivity was confined in boutons containing large granular vesicles (100-200 nm) as well as small (40-60 nm) granular vesicles. Some terminals were located in very close apposition to the pinealocyte cell membrane. Terminals were identified in perivascular spaces, but synaptic contacts between the immunoreactive terminals and pinealocytes were never observed. These data show that NPY is highly concentrated in nerve fibers throughout the rat pineal complex. Double-fluorescence histochemistry using tyrosine hydroxylase as marker for catecholaminergic fibers and NPY revealed that nearly all NPYergic fibers co-stored tyrosine hydroxylase in the superficial pineal gland. A minor portion of both immunoreactivities was not colocalized. In accordance, about 65% of the neurons in the superior cervical ganglion contained both CPON and tyrosine hydroxylase. In bilateral superior cervical ganglionectomized rats, a few NPY-ir nerve fibers remained mostly in the pineal capsule, but few fibers were also found in the superficial pineal parenchyma. Contrarily, only a moderate decrease was observed in the number of immunoreactive fibers in the deep pineal gland, and no reduction was observed in the adjacent epithalamus. In the ganglionectomised rats, co-localisation of tyrosine hydroxylase and NPY in intrapineal nerve fibers was not observed either in the superficial pineal gland, nor in the deep pineal gland. These results together with the available literature show that NPY is a sympathetic transmitter, and its actions in the pineal gland are, therefore, associated with the well-documented roles of noradrenaline. Possible roles of NPY in pineal biochemistry and physiology are discussed.

20 citations

Journal ArticleDOI
TL;DR: The results suggest that the adrenergic-stimulated cAMP signal is subjected to the tonic inhibition by phosphoprotein phosphatase, and the camp signal is more sensitive to the regulation by phosphorylation than cGMP in rat pinealocytes.
Abstract: The role of phosphoprotein phosphatase in the regulation of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) accumulation in rat pinealocytes was investigated using the three phosphatase inhibitors calyculin A, tautomycin, and okadaic acid. Calyculin A (0.1 microM) was found to enhance the isoproterenol- and norepinephrine-stimulated cAMP accumulation six- and threefold, respectively, whereas tautomycin and okadaic acid were less effective. The effect of calyculin A was rapid (within 5 min) and persisted in the presence of phosphodiesterase inhibition. However, in contrast to protein kinase C activation or intracellular calcium elevation, the phosphatase inhibitors were less effective in potentiating the cAMP response stimulated by forskolin or cholera toxin, and their effects were not blocked by calphostin C or N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide. The adrenergic-stimulated cGMP response was also less sensitive to the phosphatase inhibition. Therefore, our results suggest that 1) the adrenergic-stimulated cAMP signal is subjected to the tonic inhibition by phosphoprotein phosphatase; 2) phosphatase inhibitors enhance cAMP synthesis through their actions at the receptor level; and 3) the cAMP signal is more sensitive to the regulation by phosphorylation than cGMP in rat pinealocytes.

20 citations

Journal Article
TL;DR: It was observed that the pinealocyte cell activity of rats exposure to constant darkness was increased but decreased in rats exposed to constant light, while the number of pinealocytes observed was extensive and some of the observed Pinealocytes were determined to contain double nucleoli.
Abstract: OBJECTIVE: This study was aimed to examine the pineal gland of rats exposed to constant light and darkness at light and electron microscopic level. DESIGN: For this purpose 18 male Wistar rats were used. Animals were divided into three groups. Rats in group I (Control) were kept under 12 hrs light: 12 hrs dark conditions. Rats in group II were exposed to constant darkness, while rats in group III were exposed to constant light for 6 weeks. At the end of the experiment, all animals were killed by decapitation. The pineal glands of rats were removed, then processed for light and electron microscopy. RESULTS: In our study, extensive number of pinealocytes was observed in the structure of pineal gland of rats exposed to constant darkness and some of the observed pinealocytes were determined to contain double nucleoli. Furthermore, mitochondria and lipid droplets in the cytoplasm of pinealocytes were increased and rough endoplasmic reticulum sacs were enlarged in this group. Whereas, in rats those exposed to the constant light, a decrease in pinealocyte intensity was associated with increase in the connective tissue between parenchymal cells. Additionally, mitochondria and lipid droplets in the cytoplasm of cells were decreased. CONCLUSIONS: It was observed that the pinealocyte cell activity of rats exposed to constant darkness was increased but decreased in rats exposed to constant light.

20 citations

Journal ArticleDOI
TL;DR: It is concluded that in the rat there may be two pathways mediating the effects of light on rhythmicity, one being the retino-hypothalamic tract (RHT) utilising excitatory amino acids and the other aretino-raphe-SCN pathway utilising 5HT2c receptors.
Abstract: There is considerable interest in the neuronal pathways involved in the generation and entrainment of circadian rhythms. We have monitored the output of the pineal gland via the urinary metabolite of

20 citations

Book ChapterDOI
01 Jan 1981
TL;DR: It has been postulated that melatonin could be secreted directly into the CSF as well as into the blood, and both membrane and cytosol binding of melatonin have been described.
Abstract: It has been postulated that melatonin could be secreted directly into the CSF as well as into the blood. Is the CSF route of secretion important? The pineal is a major source of circulating melatonin. Does circulating melatonin also originate from other structures? The alternating 24-hour light/dark cycle serves as the zeitgeber for the melatonin rhythm. What event is the cue? Does increasing the hours of darkness lead to enhanced melatonin release? What is the relation of the pineal circadian rhythm to other rhythmic phenomena including rhythms in other hormones, in temperature and in locomotion? Both membrane and cytosol binding of melatonin have been described. Which type of binding is most likely to represent the physiologic receptor?

20 citations


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