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PubMed1995

Neurotrophic effects of the pineal gland: role of non-neuronal cells in co-cultures of the pineal gland and superior cervical ganglia.

The pineal gland (PG) is a source of several trophic factors. In this study, PG and superior cervical ganglia (SCG) from Sprague-Dawley neonates (1-day-old) were co-cultured to test the hypothesis that endogenous release of PG NGF (or an NGF-like cytokine) is sufficient to promote survival of SCG neurons. Neuronal density of SCG neurons was significantly enhanced when co-cultured with PG for 7 days compared to SCG cultured alone. SCG survival and neurite formation in PG co-cultures was less than in SCG treated with exogenous NGF (100 ng/ml). The neurotrophic effect of PG co-cultures was abolished when 1% anti-NGF was added to the medium. Co-cultures of SCG neurons with established 7-day PG cultures induced extensive SCG neurite formation within 24 hr compared to SCG co-cultured with 1-day PG cultures. This suggests that PG neurotrophic effects are due to PG non-neuronal cells (nnc) that proliferate to confluency by 7 days in culture. S-antigen-positive pinealocytes did not proliferate in culture. There was decreased SCG survival when neurons were seeded onto PG cultures that had been previously killed by drying, which suggests that the neurotrophic effects of nnc are not substrate-dependent. Immunocytochemical characterization of PG nnc revealed a heterogenous mixture of astrocytes, macrophage/microglia, and fibroblasts. These findings support the hypothesis that NGF is actively secreted by PG and that nnc are the principal source of this neurotophin.

Animals↗
PubMed1991

Tyrosine hydroxylase and neuropeptide-Y immunoreactivity in pineal glands developing in situ and in pineal grafts.

Postnatal development of the innervation of the pineal gland in situ as well as the reinnervation of pineal grafts by tyrosine hydroxylase (TH)- and neuropeptide Y (NPY)-immunoreactive nerve fibers were examined using the avidin-biotin-peroxidase immunohistochemical technique. TH-immunoreactive nerve fibers appeared in the pineal gland on the second postnatal day (P2) in both hamsters and gerbils. NPY-immunoreactive nerve fibers first appeared in the pineal gland of gerbils on P2 and in the hamsters on P3. By the seventh postnatal day (P7), the pineal glands of both hamsters and gerbils were richly innervated by TH- and NPY-fibers that appeared as smooth fibers or fibers with sporadic varicosities. By the age of 4 weeks, the innervation of the pineal glands of hamsters and gerbils by TH- and NPY-fibers was fully developed. Abundant TH- and NPY-fibers formed a dense meshwork in the parenchyma of the superficial and deep pineals. The great majority of the fibers bore a large number of varicosities. More NPY-fibers were found in the pineal glands of gerbils than hamsters. NPY fibers were distributed evenly throughout the pineal glands of the gerbil, but they were more often located in the central region of the superficial pineal of the hamster. For the pineal grafts, superficial pineals from neonatal and 4-week-old hamsters were transplanted to different sites in the third cerebral ventricle (infundibular recess, posterior third ventricle) or beneath the renal capsule. The pineal grafts from 4-week-old donors appeared to undergo severe degeneration and eventually disappeared. The pineal grafts from neonatal hamsters, however, successfully survived and became well integrated into their new locations. Abundant TH- and NPY-fibers in the host brain were found surrounding the pineal grafts placed in the third cerebral ventricle, but were only rarely seen entering the parenchyma of the grafts. A few TH-fibers were demonstrated in the renal grafts 4 weeks after transplantation. These studies describe the postnatal development of the innervation of the pineal glands in situ by TH- and NPY-nerve fibers, and demonstrate a lack of reinnervation of cerebroventricular pineal grafts by TH and NPY fibers from adjacent host brain.

Animals↗
PubMed2004

Primary anaplastic glio-neuronal tumor of the pineal gland: a new type of pineal neoplasm?

BACKGROUND: Tumors of the pineal gland are relatively rare. Most are solid, infiltrative lesions characterized by either germ cell, glial, or pineal parenchymal origin. To our knowledge, none have been described that contain an admixture of both anaplastic glial and neuronal elements. CASE REPORT: The authors present a case of a primary anaplastic glio-neuronal tumor of the pineal gland in a 78-year-old gentleman who presented with hydrocephalus. The patient underwent an endoscopic third ventriculostomy for treatment of his hydrocephalus as well as tumor biopsy under endoscopic visualization. RESULTS: Sections of the tumor displayed a modestly to moderately cellular neoplasm infiltrating the residual pineal gland. The majority of the nuclei appeared hyperchromatic, spindle-shaped, and pleomorphic, with fibrillary cytoplasmic processes. Rare nuclei were round with vesicular chromatin and red nucleoli. Mitotic figures were easily identified, despite small sample size. GFAP immunostaining highlighted the fibrillar background and cytoplasmic processes while synaptophysin immunostains revealed intense, dot-like positivity in the rounder nuclei with vesicular chromatin. Although the different nuclear morphologies seen on the hematoxylin-eosin stained slides suggested both glial and neuronal origin, immunostains were required to confirm the presence of dual differentiation. CONCLUSION: We present the first case of a primary anaplastic glio-neuronal neoplasm of the pineal gland. Increased use of immunostaining may unveil additional cases in the future. Furthermore, additional research will be required to determine whether the dual differentiation has prognostic significance.

Aged↗
PubMed1992

Fine structure of the pinealopetal innervation of the mammalian pineal gland.

The mammalian pineal gland is innervated by peripheral sympathetic and parasympathetic nerve fibers as well as by nerve fibers originating in the central nervous system (central innervation). The perikarya of the sympathetic fibers are located in the superior cervical ganglia, while the fibers terminate in boutons containing small granular vesicles and a few large granular vesicles. Both noradrenaline and neuropeptide Y are contained in these neurons. The parasympathetic fibers originate from perikarya in the pterygopalatine ganglia. The neuropeptides, vasoactive intestinal peptide and peptide histidine isoleucine, are present in these fibers, the boutons of which contain small clear transmitter vesicles and larger granular vesicles. The fibers of the central innervation originate predominantly from perikarya located in hypothalamic and limbic forebrain structures as well as from perikarya in the optic system. These fibers terminate in boutons containing small clear and, in certain fibers, an abundant number of large granular vesicles. In rodents, the majority of the central fibers terminate in the deep pineal gland and the pineal stalk. From these areas impulses might be transmitted further caudally to the superficial pineal gland via neuronal structures or processes from pinealocytes. Several hypothalamic neuropeptides and monoamines might be contained in the central fibers. The intrapineal nerve fibers are located both in the perivascular spaces and intraparenchymally. The majority of the intraparenchymally located fibers terminate freely between the pinealocytes. However, some nerve terminals make synaptic contacts with the pinealocytes and in some species with intrapineal neurons. In fetal mammals, sympathetic, parasympathetic, and central fibers are also present. In addition, an unpaired nerve, connecting the caudal part of the pineal gland with the extreme rostral part of the mesencephalon, is present. This nerve is a homologue to the pineal nerve (nervus pinealis) observed in lower vertebrates.

Animals↗
PubMed1979

Circadian rhythm of serotonin N-acetyltransferase activity in organ culture of chicken pineal gland.

When chicken pineal glands were organ-cultured in darkness, serotonin N-acetyltransferase activity was low during daytime, increased at midnight, and decreased on the next morning. The autonomous increase of N-acetyltransferase activity was suppressed by illumination of the glands. When pineal glands were cultured under a light-dark cycle (LD 12:12), the change of N-acetyltransferase activity continued to oscillate in phase with the light-dark cycle for 3 days.

Acetyltransferases↗
PubMed2005

Immunohistochemical demonstration of opioids and tachykinins in human pineal gland.

The human pineal gland secretes melatonin in a circadian rhythm manner. The rhythm of melatonin synthesis is primarily controlled by the noradrenergic sympathetic system originating from the superior cervical ganglion. Several neurotransmitters/neuropeptides have been reported to influence the production of melatonin in the pineal glands of many mammalian species. Both opioid peptide, a pain suppressing peptide and substance P, a pain inducing peptide were also reported to be present in the pineal gland of several kinds of mammals. However, few studies have been demonstrated in humans. Therefore, in the present study, the immunohistochemical investigation was performed in the human pineal gland by using antisera raised against leu-enkephalin, met-enkephalin and beta-endorphin to demonstrate an opioidergic system; and antisera raised against substance P, neurokinin A, and neurokinin B to study a tachykinin system. A high amount of leu- and met-enkephalin immunoreactivities were observed in intrapineal neuronal-like cells while very few were presented in nerve fibers. This result suggests a local regulatory function or paracrine opioidergic control in human pineal. Substance P- and neurokinin A-immunoreactivities, but not neurokinin B were observed in the human pineal gland. They are located mostly in nerve fibers but a few in neuronal-like cells. The tachykininergic control of human pineal is mainly from the nerve fibers which have their perikaryal origin outside the gland. Some of the nerve fibers might originate from neurons in the brain and/or from a peripheral ganglion.

Cadaver↗
PubMed2005

The expression of alpha-internexin and peripherin in the developing mouse pineal gland.

The mammalian pineal gland contains pinealocytes, interstitial glial cells, perivascular macrophages, neurons and neuron-like cells. The neuronal identity of neurons and neuron-like cells was an enigma. alpha-Internexin and peripherin are specific neuronal intermediate filament proteins and are expressed differentially in the CNS and PNS. We investigated the development of immunoreactivity and expression patterns of mRNAs for alpha-internexin and peripherin in the mouse pineal gland to determine the neuronal identity of these cells. Both alpha-internexin- and peripherin-immunoreactive cells were readily visualized only after birth. Both proteins were at the highest level on the postnatal day 7 (P7), rapidly declined at P14, and obtained their adult level at P21. Both protein and mRNA of alpha-internexin are expressed in some cells and nerve processes, but not all, of adult mouse pineal gland. Less number of peripherin immunoreactive or RNA-expressing cells and nerve processes were identified. Accumulations of alpha-internexin and peripherin proteins were also found in the cells from the aged pineal gland (P360). We concluded that some cells in the developing mouse pineal gland may differentiated into neurons and neuron-like cells expressing both alpha-internexin and/or peripherin only postnatally, and these cells possess dual properties of CNS and PNS neurons in nature. We suggested that they may act as interneurons between the pinealocyte and the distal neurons innervating the pinealocytes, or form a local circuitry with pinealocytes to play a role of paracrine regulatory function on the pinealocytes.

Animals↗
PubMed1998

[The effect of various wave lengths of light and various duration of impulse times on suppression of n-acetyltransferase activity in the rat pineal gland].

PURPOSE: Rat pineal gland synthesizes melatonin in circadian rhythm, with peak values in a dark phase of an imposed light-dark illumination cycle. Light is the most important environmental factor regulating the melatonin-generating system in this gland. Exposure to light causes a dramatic decline of the night-time levels of these melatoninergic parameters. Effect of white and monochromatic lights of various wavelength on the night-time pineal gland serotonin N-acetyltransferase (NAT) activity was examined in rats. MATERIAL AND METHODS: Wistar rats (12 weeks old) were used. All animals were offered ad libitum access to standard food and water, maintained under an ambient temperature of 21 +/- 2 degrees C, 60 +/- 5% humidity, and exposed to 12 hr light: 12 hr dark illumination cycle for a minimum of 10 days before experiments. The day-time light intensity at the surface of the animals' cages was about 150 luxes. Each experiment was performed at least twice. During the fifth hour of the dark phase of the light-dark illumination cycle individually housed rats were exposed to either white or monochromatic light for 15 sec., 1, 5 or 15 min, and then killed by decapitation. Control animals were quickly decapitated under dim red light (2 luxes). Pineal glands were dissected out and frozen on dry ice. Five rats were sacrificed at each time point. Exposure of animals to light took place in 25 x 21 cm white plastic chamber. Light produced by 5 W 14 bulb (Osram) was passed through a cotton filter or narrow band interference filters, filtered with glass, +/- 7 nm half-peak band-width. The spectral wavelength analysis for each interference filter was performed with the aid of Diode-Spectrophotometer, and irradiance of the light of the three used wavelengths was measured with YSI Radiometer. The estimated peak wavelengths (lambda max) of the filters were: 434 nm (blue), 548 nm (green) and 614 nm (red). The NAT activity was determined in supernatants of tissue homogenates by the radioisotopic method of Steinlechner with Nowak's modifications. RESULTS: NAT of rat pineal gland is very sensitive to the inhibition by light and the marked decline of the night-time NAT activity was observed after 15-sec. pulse of either white or green light (by 44%-white light and 37%-green light). Exposure of rats to white, green, and blue lights for 1 min. decreased NAT pineal activity by 56%, 46%, and 21%, respectively, while the 1 min. pulse of red light did not significantly alter the enzyme activity. CONCLUSION: Interestingly, exposure of rats to any tested lights for as long as 15 min. suppressed NAT activity of rat pineal gland to similar extent, reaching 8-9% of the dark control value.

Animals↗
PubMed2004

Daily rhythm and regulation of clock gene expression in the rat pineal gland.

Rhythms in pineal melatonin synthesis are controlled by the biological clock located in the suprachiasmatic nuclei. The endogenous clock oscillations rely upon genetic mechanisms involving clock genes coding for transcription factors working in negative and positive feedback loops. Most of these clock genes are expressed rhythmically in other tissues. Because of the peculiar role of the pineal gland in the photoneuroendocrine axis regulating biological rhythms, we studied whether clock genes are expressed in the rat pineal gland and how their expression is regulated.Per1, Per3, Cry2 and Cry1 clock genes are expressed in the pineal gland and their transcription is increased during the night. Analysis of the regulation of these pineal clock genes indicates that they may be categorized into two groups. Expression of Per1 and Cry2 genes shows the following features: (1) the 24 h rhythm persists, although damped, in constant darkness; (2) the nocturnal increase is abolished following light exposure or injection with a beta-adrenergic antagonist; and (3) the expression during daytime is stimulated by an injection with a beta-adrenergic agonist. In contrast, Per3 and Cry1 day and night mRNA levels are not responsive to adrenergic ligands (as previously reported for Per2) and daily expression of Per3 and Cry1 appears strongly damped or abolished in constant darkness. These data show that the expression of Per1 and Cry2 in the rat pineal gland is regulated by the clock-driven changes in norepinephrine, in a similar manner to the melatonin rhythm-generating enzyme arylalkylamine N-acetyltransferase. The expression of Per3 and Cry1 displays a daily rhythm not regulated by norepinephrine, suggesting the involvement of another day/night regulated transmitter(s).

Adrenergic beta-Agonists↗
PubMed1991

S-antigen and glial fibrillary acidic protein immunoreactivity in the in situ pineal gland of hamster and gerbil and in pineal grafts: developmental expression of pinealocyte and glial markers.

Postnatal development of S-Ag and GFAP immunoreactivity in the in situ pineal glands of golden hamsters and gerbils was examined using the avidin-biotin-peroxidase immunohistochemical technique. S-Ag was present in the gerbil pineal gland on the first postnatal day (P1), whereas it did not appear in the hamster pineal until P6. GFAP-immunoreactive astrocytes were first observed in the hamster pineal gland on P7 and in the gerbil pineal gland on P10. The number of S-Ag-immunoreactive pinealocytes and GFAP-immunoreactive astrocytes in the pineal glands of hamsters and gerbils increased with increasing age from P7 to 3 weeks. By 4 weeks, strong S-Ag and GFAP immunoreactivity was observed in both hamster and gerbil pineal glands. GFAP-immunoreactive stellate astrocytes were distributed evenly throughout the gerbil superficial pineal gland, but they were more often located in the peripheral region of the hamster superficial pineal. For the pineal grafts, pineal glands from neonatal (3-5 day old) hamsters were transplanted into the third cerebral ventricle (infundibular recess or posterior third ventricle) or beneath the renal capsule of adult male hamsters. S-Ag immunoreactivity appeared in the pineal grafts within 1 week following transplantation. By 4 weeks the pineal grafts showed strong S-Ag immunoreactivity which was maintained until at least 12 weeks after transplantation. The time course of glial cell maturation in the cerebroventricular pineal grafts is generally parallel to the hamster pineal gland in situ before 4 weeks. By 12 weeks, however, more astrocytes differentiated and developed GFAP-immunoreactivity in the pineal grafts than in the in situ pineals. These studies have described the postnatal development of S-Ag and GFAP immunoreactivity in in situ pineal glands and in neonatal pineal grafts.

Animals↗
PubMed1990

Pineal gland as a model to elucidate the primary mode of action of alpha-methyldopa: alpha-methyldopa induces an increase in the synthesis of N-acetylserotonin and melatonin levels by the rat pineal gland.

An attempt was made to use the pineal gland as a model for the study of the primary mode of action of alpha-methyldopa, which is still unclear. Organ cultures of pineal glands from rats treated chronically with alpha-methyldopa showed enhanced conversion of radio-active serotonin to melatonin (aMT) as well as its precursor, N-acetyl-serotonin (aHT). This treatment was also found to raise serotonin-N-acetyltransferase (NAT) activity. These increases associated with alpha-methyldopa treatment were further enhanced by the beta-adrenergic agonist, isoproterenol, suggesting a supersensitivity-type effect occurring at the level of the beta-receptor. A subsequent binding study, however, showed a decrease in beta-receptor binding with exposure to alpha-methyldopa, providing mitigating evidence against the occurrence of a supersensitivity phenomenon. It is possible that a metabolite of alpha-methyldopa acts as an alpha 1 and beta-agonist, resulting in greater melatonin (aMT) and N-acetylserotonin (aHT) synthesis than by a beta-agonist, isoproterenol.

Animals↗
PubMedDate not supplied

Vasopressin and oxytocin modulation of melatonin secretion from rat pineal glands.

The rat pineal gland is known to release melatonin in response to noradrenergic stimulation. Since vasopressin (VP)- and oxytocin (OT)-containing fibers innervate the pineal gland, the effects of VP and OT on melatonin release from perifused rat pineal glands were investigated. VP (10(-7) M) and OT (10(-6) M) decreased the basal melatonin secretion. No dose-dependent effect was observed. At high concentrations (10(-5)) these peptides potentiated the isoproterenol-induced increase of melatonin secretion. Below 10(-5) M no potentiation was observed. Fragments of VP ([pGlu4,Cys6]VP(4-9] and OT (pGlu4,Cys6]OT(4-9] did not display any effect on the isoproterenol-induced melatonin secretion.

Animals↗
PubMed2001

Expression and role of phosphodiesterase 6 in the chicken pineal gland.

The chicken pineal gland is directly photosensitive, with light causing an inhibition of melatonin synthesis. A possible role of phosphodiesterase 6 (PDE6, the primary effector of retinal phototransduction) in mediating this response was investigated. RT-PCR, DNA sequencing and northern blots revealed the presence of RNA encoding both catalytic and regulatory subunits of PDE6 in the chicken pineal gland. Both rod and cone forms of PDE6 subunits mRNA were detected. The concentration of the transcripts encoding PDE6 catalytic subunits peaked at night. Western blot analysis of chicken pineal proteins with an antibody directed against the catalytic subunits of bovine rod PDE6 identified a single immunoreactive protein of 97 kDa. Anion exchange chromatography of chicken pineal soluble proteins revealed a peak of PDE6 activity that accounted for about 30% of cyclic GMP-hydrolysis. In cultured chick pineal glands, arylalkylamine N-acetyltransferase (AA-NAT), the rate-limiting enzyme of melatonin synthesis, was protected from inhibition by light when selective PDE5/6 inhibitors (zaprinast, DMPPO) were added to the culture medium. PDE5/6 inhibitors did not affect AA-NAT activity in the dark. In contrast, a general PDE inhibitor (IBMX) increased AA-NAT in a light-independent manner. Together, the data indicate that rod and cone forms of PDE6 are expressed in chick pineal cells and that this enzyme plays a role in the inhibition of melatonin synthesis by light.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

The presence and actions of opioid receptors in bovine pineal gland.

The mammalian pineal gland and its main hormone, melatonin, working in conjunction with the hypothalamic suprachiasmatic nuclei, synchronize circadian rhythm and hence refine numerous physiological and biochemical parameters. An interaction among melatonin, opioids, and analgesia has been suspected for many years, since during nighttime, when the level of melatonin is high, the mammals are less sensitive to pain. In studying this phenomenon further, we have identified a single population of opioid receptors in the bovine pineal gland using [3H]-diprenorphine and other ligands. The receptors have a dissociation equilibrium constant (Kd) of 1.36 +/- 0.31 nM and a density (Bmax) of 17.93 +/- 5.22 fmol/mg protein. In competitive experiments, the concentration of drugs required to inhibit 50% of the [3H]-diprenorphine binding (IC50) in descending order of potency was found to be naltrexone > fentanyl > naloxone > nalbuphine > morphine > nalorphine > DAGO > dynorphin > metenkephalin. In order to delineate the function of the opioid system in the pineal gland, the effects of both opioid receptor agonists and antagonists on the basal activity of N-acetyltransferase were examined in the bovine pineal explants in culture. Morphine, an opioid receptor agonist, increased significantly the activity of N-acetyltransferase in a dose-dependent fashion. In addition, the stimulatory effect of morphine was inhibited by naloxone, an opioid receptor antagonist. The results of these studies indicate the existence of pineal opioid receptors, which play a pivotal role in the synthesis of melatonin and its action in synchronizing pineal events.

Animals↗
PubMed2003

Dephosphorylation of pCREB by protein serine/threonine phosphatases is involved in inactivation of Aanat gene transcription in rat pineal gland.

The rat pineal gland is a suitable model to investigate neurotransmitter-controlled gene expression, because it is well established that the stimulation of melatonin biosynthesis by norepinephrine (NE) depends on the activation of the gene that encodes arylalkylamine N-acetyltransferase (AANAT), the melatonin rhythm enzyme. The mechanisms responsible for downregulation of Aanat transcription are less clear. In this in vitro study we investigated the role of pCREB dephosphorylation for termination of Aanat gene transcription. Immunosignals for pCREB, strongly induced after NE stimulation, rapidly decreased after withdrawal of NE. The immunoreactivity of the inhibitory transcription factor ICER increased twofold after NE treatment for 6 h, but did not change within 30 min after removal of the stimulus. Application of protein serine/threonine phosphatase (PSP) inhibitors prevented pCREB dephosphorylation and blocked the decreases in Aanat mRNA levels, AANAT protein amount and melatonin biosynthesis all of which occurred rapidly after NE withdrawal. PSPs in the rat pineal gland were characterized by immunocytochemistry and immunoblotting. NE-stimulation for 8 h induced accumulation of PSP1-catalytic subunit (CSU) in pinealocyte nuclei, but did not affect the distribution of PSP2A-CSU. The results identify dephosphorylation of pCREB by PSPs as an essential mechanism for downregulation of Aanat transcription in the rat pineal gland.

Animals↗