SEARCH · PubMed Health

Results for “PINEAL GLAND”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources

PubMed1989

Role of postsynaptic alpha-adrenergic receptors in the beta-adrenergic stimulation of melatonin production in the Syrian hamster pineal gland in organ culture.

The role played by postsynaptic alpha-adrenergic receptors in the stimulation of pineal melatonin production was investigated in the Syrian hamster. The studies were conducted using organ cultured pineal glands collected from both anatomically intact and superior cervical ganglionectomized hamsters. Results obtained indicate that phenylephrine, an alpha-adrenergic agonist, by itself has no effect in promoting melatonin production; however, it potentiates the stimulatory effects of isoproterenol, a beta-adrenergic agonist, on pineal melatonin production in nonoperated hamsters. Similar observations were obtained with pineal glands whose presynaptic terminals were removed by prior superior cervical ganglionectomy. However, a longer incubation time was required (4-6 hours vs. 2 hours) with pineal glands taken from ganglionectomized animals. Apparently, beta-adrenergic activation is an absolute requirement to stimulate pineal melatonin production, and an alpha-adrenergic receptor mechanism potentiates beta-adrenergic activation. In addition, the findings obtained with denervated pineal glands suggest that the regulation of pineal melatonin production by both alpha- and beta-adrenergic mechanisms is through receptors located on postsynaptic structures.

Animals↗

PubMed2005

[Circadian rhythms and light responses of clock gene and arylalkylamine N-acetyltransferase gene expressions in the pineal gland of rats].

This study was to investigate the circadian rhythms and light responses of Clock gene and arylalkylamine N-acetyltransferase (NAT) gene expressions in the rat pineal gland under the 12 h-light : 12 h-dark cycle condition (LD) and constant darkness (DD). Sprague-Dawley rats housed under the light regime of LD (n=36) for 4 weeks and of DD (n=36) for 8 weeks were sampled for the pineal gland once a group (n=6) every 4 h in a circadian day. The total RNA was extracted from each sample and the semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine the temporal changes in mRNA levels of Clock and NAT genes during different circadian times or zeitgeber times. The data were analysed by the cosine function software, Clock Lab software and the amplitude F test was used to reveal the circadian rhythm. The main results obtained are as follows. (1) In DD or LD condition, both of Clock and NAT genes mRNA levels in the pineal gland showed robust circadian oscillation (P< 0.05) with the peak at the subjective night or at night-time. (2) In comparison with DD regime, the amplitudes and the mRNA levels at peaks of Clock and NAT genes expressions in LD in the pineal gland were significantly reduced (P< 0.05). (3) In DD or LD condition, the circadian expressions of NAT gene were similar in pattern to those of Clock gene in the pineal gland (P> 0.05). These findings suggest that the expressions of Clock and NAT genes in the pineal gland not only show remarkably synchronous endogenous circadian rhythmic changes, but also response to the ambient light signal in a reduced manner.

Animals↗

PubMed1999

Innervation of the rat pineal gland by pituitary adenylate cyclase-activating polypeptide (PACAP)-immunoreactive nerve fibres.

Pituitary adenylate cyclase-activating polypeptide (PACAP)-immunoreactive nerve fibres were demonstrated in the rat pineal gland. These fibres entered the pineal gland through the conarian nerve at the distal tip of the gland. A high density of the fibres was observed in the capsule of the gland, from where the immunoreactive elements penetrated into the pineal perivascular spaces and parenchyma. The majority of PACAP-immunoreactive nerve fibres also contained calcitonin gene-related peptide (CGRP). Some PACAP-immunoreactive nerve fibres contained neuropeptide Y (NPY), but only occasionally was PACAP colocalized with vasoactive intestinal peptide (VIP). After removal of both superior cervical ganglia, a high number of PACAP-containing nerve fibres were still present in the gland. In the nervous system PACAP is present in two isoforms, PACAP-38 and PACAP-27. The concentration of PACAP-38 in the superficial pineal gland was determined by radioimmunoassay to be 20.4 pmol/g tissue at midday and 18.9 pmol/g tissue at midnight. The concentration of PACAP-27 was only about 3% of the concentration of PACAP-38. In summary, this study is the first demonstration of a PACAP-containing innervation of the rat pineal gland. The PACAP concentration in the pineal gland does not exhibit a day-night difference. The colocalization of PACAP with calcitonin gene-related peptide in the pincalopetal nerve fibres indicates that the majority of PACAP-immunoreactive nerve fibres might originate from the trigeminal ganglion.

Animals↗

PubMed2001

Microvascularisation of the pineal gland in the rat.

The authors investigated the pineal blood supply in the rat, including microvascularisation, using different methods of vascular corrosion cast technique and two methods of inspection: scanning electron microscopy (SEM) and light microscope (LM). The animals were divided into three groups and injected with two types of casting media. It was found that the pineal gland is highly vascularised. Arterial supply is from the branches of the medial posterior choroidal artery which originates from the posterior cerebral artery. All veins drain into the great cerebral vein directly without forming the pineal vein. However, we noticed a short venous trunk between the great cerebral vein and the confluence of the sinuses. This venous trunk had not been described in literature till now and does not have a name in anatomical nomenclature. The authors showed the relationship of the pineal gland to adjacent venous vessels.

Animals↗

PubMed1991

Acetylation of serotonin in the rabbit pineal gland: an N-acetyltransferase with properties distinct from NAT1 and NAT2 is responsible.

Two rabbit arylamine N-acetyltransferases (NAT1 and NAT2, EC 2.3.1.5) have been cloned and characterized recently in this laboratory. They catalyze the acetylation of primary arylamine and hydrazine drugs and other substrates in the liver, including sulfamethazine, p-aminosalicylic acid, and p-aminobenzoic acid. In the pineal gland, serotonin is metabolized to N-acetylserotonin by an unknown N-acetyl-transferase. Similarity of the liver enzymes and the pineal gland arylalkylamine N-acetyltransferase (AA-NAT) has been suggested, because pineal gland homogenates were shown to metabolize arylamine substrates as p-phenetidine, aniline, or phenylethylamine, and liver homogenates or partially purified liver enzyme preparations catalyzed the N-acetylation of serotonin. The present study was undertaken to elucidate the possible role of NAT1 or NAT2 in serotonin acetylation in the pineal gland. We transiently expressed rNAT1 and rNAT2 genes in COS cells, studied the kinetics of the enzymes produced with various substrates, and compared these data with activities of rabbit pineal glands and livers. These enzymatic studies were complemented with western blot analysis with antibodies against NAT1 and NAT2. Cross-hybridization of rNAT1 or rNAT2 to the gene for the pineal gland AA-NAT was tested by Southern blot studies of genomic rabbit DNA. Our results indicate that although NAT1 is expressed in the pineal gland, it is not involved in the physiologically important step of N-acetylation of serotonin.

Acetylation↗

PubMed2005

Sympathetic neuroaxonal dystrophy in the aged rat pineal gland.

Dysfunction of circadian melatonin production by the pineal gland in aged humans and rats is thought to reflect the functional loss of its sympathetic innervation. Our ultrastructural neuropathologic studies of the sympathetic innervation of the pineal gland of aged (24 months old) Fischer-344 and Sprague-Dawley rats showed loss of nerve terminals as well as the development of neuroaxonal dystrophy (NAD), an ultrastructurally distinctive distal axonopathy, far in excess of that in young control rats. Immunolocalization of tyrosine hydroxylase confirmed the age-related loss of normal noradrenergic innervation and development of NAD. NAD was more frequent in aged female rats compared to males and was particularly severe in aged female Sprague-Dawley rats compared to Fischer-344 rats. Pineal NGF content was significantly increased or unchanged in female and male aged Fischer-344 rats, respectively, compared to young controls. The rat pineal is a sensitive experimental model for the quantitative ultrastructural examination of age-related neuropathological changes in nerve terminals of postganglionic noradrenergic sympathetic axons, changes which may reflect similar changes in the diffusely distributed sympathetic innervation of other targeted endorgans.

Aging↗

PubMed1993

The pineal gland in human beings: relevance to pediatrics.

Several facts suggest that the pineal gland must have a significant role in human beings: the presence of melatonin secretion from infancy to old age; a circadian secretory pattern similar to that found in animal species in which this gland has well-defined functions; its responsiveness to light; and the presence of melatonin receptors in the hypothalamus. Despite the importance of the pineal gland and melatonin in the reproductive activity of all nonprimate vertebrate species studied, the relationship of melatonin secretion to the activity of the hypothalamic-pituitary-gonadal axis in human beings remains presumptive. Some data suggest a possible pineal-reproductive connection throughout the human lifespan, but new research approaches are needed for a better definition of this connection during normal development and in disorders of the reproductive axis. In addition, recent studies that have applied strictly defined techniques to unravel the masking effects of various behavioral and environmental factors suggest that the pineal gland and melatonin have a fundamental role in the regulation of the human biologic clock. Melatonin concentrations in blood or urine may become a useful marker of the circadian rhythm in disorders of rhythms. Moreover, administration of melatonin in physiologic or pharmacologic doses may have an important application in suppression of the hypothalamic-pituitary-gonadal axis as a contraceptive, and in therapy for disorders of biologic rhythms. Among the latter, of particular interest to the pediatric population will be the potential application of melatonin treatment in establishing or reestablishing circadian rhythms in infants and children maintained for long periods under artificial light conditions, as encountered in intensive care units, and in the treatment of sleep and other rhythm disorders associated with developmental delay or blindness. Further research and approval by the U.S. Food and Drug Administration will be required before these applications will be available to the practicing pediatrician. The identification of melatonin receptors in the human hypothalamic fetal and adult tissues and the development of potent melatonin agonists and antagonists have paved the way for new research approaches that are needed to further investigate this intriguing, long-forgotten gland in human beings.

Humans↗

PubMed1984

Sex-related differences in pineal gland N-acetyltransferase induction by d-amphetamine.

The activity of the rat pineal gland enzyme, N-acetyltransferase (NAT), was measured to determine if amphetamine stimulation of norepinephrine release from sympathetic fibers innervating the gland varies according to sex-dependent mechanisms. Pineal gland NAT activity was increased following amphetamine treatment to a greater extent and for a longer duration in adult female rats compared to male animals. The greater in vivo stimulation of adult female pineal gland NAT activity by the drug developed after puberty, depended upon intact gonads, and apparently was not due to sex differences in the amount of norepinephrine released by the drug from sympathetic nerves when tested under in vitro conditions. The in vivo sex dependent effects of amphetamine may be related to the lesser rate at which the drug is metabolized and/or excreted by female rats compared to males.

Acetyltransferases↗

PubMed1978

Electron microscopic observations on neuron-like cells in the ground squirrel pineal gland.

Ultrastructural details of neuron-like cells as well as synaptic nerve endings in the pineal gland of the ground squirrel are described. The neuron-like cells are situated mainly in the distal portion of the gland. Since the neuron-like cells differ considerably from the pinealocytes and exhibit cytological features characteristic of nerve cells, they are presumably true neurons. The cell bodies or processes of the neuron-like cells receive many synapses. The nerve endings synapsing on these cells contain numerous small non-granulated and some large granulated vesicles but no small granulated vesicles. These synaptic nerve endings are rather abundant within the parenchyma but they are also found in perivascular spaces ensheathed completely or partially by the Schwann cell cytoplasm. Similar nerve endings occasionally make typical synaptic contacts with the cell bodies or processes of the pinealocytes. Since the adrenergic nerve endings do not form synapses on the pinealocytes in the ground squirrel, it is clear that nerve endings other than adrenergic ones also distribute within the pineal gland of this animal. These synaptic nerve endings may contribute, at least to some extent, to the innervation of the ground squirrel pineal gland, whether they are derived from the nerve fibers penetrating the pineal gland or from the neuron-like cells.

Adrenergic Fibers↗

PubMed1998

Pituitary adenylate cyclase-activating polypeptide rhythm in the rat pineal gland.

Pituitary adenylate cyclase-activating polypeptide (PACAP) was recently demonstrated to stimulate melatonin synthesis in the rat pineal gland. Circadian rhythms of melatonin concentration are well known. However, it has not been clarified whether PACAP contents in the pineal gland show circadian rhythm. In this study, we measured PACAP contents in the rat pineal gland throughout the day under 12:12 h light-dark cycle or constant dark conditions. A significant fluctuation was observed in the PACAP content under light-dark conditions but not under constant darkness. On the other hand, the pituitary gland showed no significant variation throughout the day under either conditions. These observations suggest that PACAP may participate in the modulation of melatonin synthesis depending on light conditions in the pineal gland.

Analysis of Variance↗

PubMed1987

Aminergic innervation pattern of the rodent pineal gland: no apparent influence of time of day.

Pineal melatonin synthetic activity shows distinct diurnal characteristics. The circadian regulation of melatonin synthesis is provided by noradrenaline-releasing sympathetic nerves. The pineal noradrenaline content shows a circadian rhythmicity tidally related to the changes in melatonin synthesis rate. To evaluate possible circadian changes of pineal noradrenergic fibre arrangement, the nerve distribution in rat and guinea pig pineal glands was visualized by means of glyoxylic acid-induced histofluorescence. Histochemical findings at 08.00 h and 24.00 h did not exhibit any differences: in both species a dense, mainly perivascularly located network of fluorescent fibres was encountered. As indicated by the simultaneous intraneural presence of green-bluish and yellow fluorophores these fibres most likely contain noradrenaline and serotonin. Obviously circadian melatonin synthesis changes are not paralleled by changes in the distribution pattern of pineal sympathetic nerve fibers. Like other sympathetic innervation-related morphological parameters, histofluorescence does not accurately reflect circadian biochemical changes in the pineal gland.

Adrenergic Fibers↗

PubMed1996

Nitric oxide synthase in the pineal gland.

The recent discovery of nitric oxide (NO) as a biological messenger molecule with unique characteristics has opened a new field in pineal research. This free radical gas is synthesized by the enzyme nitric oxide synthase (NOS) from L-arginine. The activation of adrenoreceptors in the membrane of the pinealocytes mediates the increase in NO through a mechanism that involves G proteins. In the pinealocyte, NO stimulates guanylyl cyclase resulting in an increased intracellular content of cGMP. The role of cGMP in pineal metabolism, however, is still enigmatic. Using enzyme histochemistry and immunohistochemistry, the presence of NOS has been confirmed in the pineal gland of some species. In the rat and especially in the sheep, NOS is located in nerve fibres innervating the gland. These nerve fibres also contain the neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI), and are probably of parasympathetic origin. In cell cultures and tissue sections NOS immunoreactivity has been shown to be present in pinealocytes of the rat and bovine but not in the sheep. Finally, NOS is also present in the endothelial cells of the blood vessels of the pineal gland. Accordingly, in the mammalian pineal gland, NO is synthesized in both presynaptic nerve fibers and pinealocytes, as well as in blood vessels. However, the anatomical location of NO synthesis varies considerably among species. NO released in the pineal gland, might influence both the pineal metabolism and the blood flow of the gland.

Animals↗

PubMed1997

Circadian oscillations of lipid peroxides in the rat pineal gland.

We studied the circadian oscillation of lipid peroxides (TBARS) in the pineal gland of rats adapted to light:dark 12:12 h regimen. The concentration of TBARS was determined at 3-h intervals during 24 hours. TBARS of pineal gland oscillated rhythmically during the 24 h period. The maximal concentration of lipoperoxidative products was found at 20.00 h and 02.00 h and the lowest values at 08.00 h and 23.00 h. The determination of antioxidant capacity is needed for explaining the mechanism of TBARS oscillations in the pineal gland.

Animals↗

PubMed1991

Circadian rhythms of melatonin secretion from superfused goldfish (Carassius auratus) pineal glands in vitro.

A flow-through, whole-organ culture (superfusion) system was developed, and goldfish pineal glands were maintained at 25 degrees under light-dark (LD) 12:12 cycles, reversed LD 12:12 cycles, continuous dark (DD), or continuous light (LL) conditions for 48 hr. Under LD 12:12 and reversed LD 12:12 cycles, superfused pineal glands showed a rhythmic melatonin secretion: Scotophase was associated with high titers and photophase with low titers. The melatonin secretion rhythms persisted for two cycles under DD conditions, whereas nocturnal rises were suppressed under LL conditions. After the transition from LL to DD conditions on the third day, melatonin showed a nocturnal increase. These results indicate that melatonin secretion from the superfused goldfish pineal gland is directly photosensitive and that the goldfish pineal gland harbors a circadian oscillator which generates melatonin secretion rhythms.

Animals↗

PubMed1991

Identification and characterization of alpha 2D-adrenergic receptors in bovine pineal gland.

The vertebrate mechanisms for generating circadian rhythms, regulating the synthesis of melatonin, and modulating the activities of pineal indole-synthesizing enzymes differ significantly among species. The synthesis of melatonin in mammalian pineal glands is stimulated by beta 1-adrenergic receptor agonists and is potentiated by alpha 1-adrenergic receptor agonists, whereas in the avian pineal gland alpha 2-adrenergic receptor agonists inhibit its synthesis. By using [3H]rauwolscine, a selective alpha 2-adrenergic receptor antagonist, we have identified for the first time alpha 2-adrenergic receptor sites in a mammalian pineal gland. [3H] Rauwolscine bound in a saturable manner to a single class of receptors, with an equilibrium dissociation constant (KD) of 1.4 nM and a density (Bmax) of 71 fmol/mg of protein, in crude synaptic membrane preparations from bovine pineal gland. Competition studies carried out with various adrenergic antagonists supported the conclusion that [3H]rauwolscine binding sites were alpha 2-adrenergic receptors. The bovine pineal alpha 2-adrenergic receptor appears to represent a pharmacological subtype distinct from the three currently proposed subtypes, i.e., alpha 2A found in a human colonic adenocarcinoma cell line (HT29 cell), alpha 2B found in rat lung, and alpha 2C found in an opossum kidney cell line (OK cell). However, the pharmacologic profile of the pineal alpha 2 receptor resembles that found in the rat submaxillary gland. We suggest that the bovine pineal receptor may represent a fourth pharmacological subtype, which would be designated as alpha 2D.

Animals↗

PubMedDate not supplied

The pineal gland and reproduction.

The hormonal activity of the pineal gland is influenced by both the dark-light cycle and the seasonal cycle, causing it to play an important role in the neuroendocrine control of reproductive physiology. This is especially evident in seasonally breeding animals, in which reproductive function is clearly influenced by seasonal variations in the duration of night and day. Humans are not seasonal breeders. Nevertheless, seasonal fluctuations have been described in human reproduction, and the pineal gland also appears to exert an important role in the neuroendocrine regulation of human reproductive physiology. There is evidence that the epiphysis is involved in the control of sexual maturation. In rats, the maternal pineal appears to influence the gonadal and genital development and function of offspring; this hypothesis has yet to be confirmed in humans. The pineal apparently influences human reproductive function not only at the hypothalamic-pituitary level, by inhibition of the hypothalamic pulsatile secretion of gonadotrophin-releasing hormone, but also at the gonadal level, where melatonin receptors have also been found. In addition, melatonin is reported to increase serum prolactin concentrations in both rats and humans. It has been suggested that melatonin is involved in the control of menstrual cyclicity.

Animal Husbandry↗

PubMed1987

Methiothepin enhances the potassium-evoked release of [3H]-noradrenaline in rat pineal gland.

The 5-hydroxytryptamine (5-HT) autoreceptor antagonist methiothepin increased in a concentration-dependent manner the K+-evoked release of [3H]-noradrenaline in pineal glands from normal and parachlorophenylalanine (PCPA)-treated rats. However, 5-HT and the 5-HT receptor agonists, LSD and 5-methoxytryptamine, were inactive at modulating the K+-evoked release of [3H]-noradrenaline in pineal glands from normal and PCPA-treated rats. When tested on the uptake of [3H]-noradrenaline in the pineal gland, methiothepin was found to be a potent inhibitor (IC50 = 10.6 nmol/l). Exposure to methiothepin failed to increase the K+-evoked release of [3H]-noradrenaline when tested in the presence of cocaine. While the K+-evoked release of [3H]-noradrenaline was shown to be modulated through inhibitory presynaptic alpha 2-adrenoceptors in pineal glands from normal and PCPA-treated rats, no evidence was obtained for a presynaptic modulation through 5-HT receptors of [3H]-noradrenaline release. The facilitation by methiothepin of the K+-evoked release of [3H]-noradrenaline in rat pineal gland appears to be due to the inhibition of noradrenaline uptake by this compound.

Animals↗

PubMed1994

Formation, metabolism, and action of hepoxilin A3 in the rat pineal gland.

The present study was undertaken to investigate the possible formation of hepoxilin A3 in the rat pineal gland and to study the potential physiological role for this compound in this tissue. Incubation of homogenates of rat pineal glands with arachidonic acid (66 microM) led to the appearance of hepoxilin A3 (HxA3) analyzed as its stable trihydroxy derivative, trioxilin A3 by gas chromatography in both the electron impact and negative ion chemical ionization modes. Endogenous formation of HxA3 is estimated to be 1.43 +/- 0.66 ng/micrograms of protein. This amount is not modified when the tissue is boiled (2.07 +/- 0.66 ng/micrograms of protein). However, the formation of this compound was stimulated to 21.26 +/- 5.82 ng/micrograms of protein when exogenous arachidonic acid was added to the homogenate. Addition of the dual cyclooxygenase/lipoxygenase inhibitor BW 755C (10 micrograms) resulted in a partial blockade of hepoxilin formation. Using [1-14C]HxA3, we demonstrated that the pineal gland contained hepoxilin epoxide hydrolase, which hydrolyzed HxA3 into trioxilin A3. This hydrolysis was inhibited by 1 mumol/L of 3,3,3-trichloropropene-1,2-oxide. In a separate study, HxA3 in the presence of 3,3,3-trichloropropene-1,2-oxide to block the hydrolysis of HxA3 decreased the production of cyclic AMP in cultured organ rat pineals after stimulation with 5'-N-ethylcarboxamidoadenosine, an A1/A2 adenosine receptor agonist. This effect is stereospecific because the (8S)-enantiomer is more active in decreasing cyclic AMP production (-88.7%) than the (8R)-enantiomer. This is the first demonstration of the presence, metabolism, and action of HxA3 in the rat pineal gland.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗