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At least 865 records · Page 48Linked to original sources

PubMed1979

Influence of the pineal gland, olfactory bulbs and photoperiod on surges of plasma prolactin in the female rat.

The role of the pineal gland, olfactory bulbs and photoperiod in the regulation of the two daily surges of plasma prolactin in the pseudopregnant rat has been investigated. Pinealectomy had no effect on the surges of prolactin in pseudopregnant rats maintained on either a long (14 h light : 10 h darkness; 14L : 10D) or a short (2L : 22D) photoperiod, but olfactory bulbectomy decreased the nocturnal surge in animals maintained on 14L : 10D. This effect of bulbectomy was eliminated if the rats maintained on 14L : 10D were also pinealectomized. After cervical stimulation, bulbectomized rats maintained on a 2L : 22D photoperiod had nocturnal-type prolactin surges similar to those of intact rats maintained on the same photoperiod. These results indicate that the pineal gland andlength of photoperiod are not involved in the regulation of the surges of plasma prolactin in pseudopregnant rats but that the olfactory bulbs may enhance the nocturnal surge.

Animals↗

PubMed2005

Pineal circadian clocks gate arylalkylamine N-acetyltransferase gene expression in the mouse pineal gland.

In mammals it has been thought that the circadian clock localizes only in the suprachiasmatic nucleus of the hypothalamus. Recent studies have revealed that certain brain regions and peripheral tissues may also have intrinsic circadian clocks. However, the roles played by 'peripheral circadian clocks' have not been fully elucidated. In this study, we investigated their function using mouse pineal glands, and found that expression of the arylalkylamine N-acetyltransferase (Aa-Nat, EC 2.3.1.87, the rate-limiting enzyme of melatonin synthesis) gene after adrenergic receptor stimulation depended on the time of day even in vitro (gating). Phase-dependent Aa-Nat responses were observed in both melatonin-proficient and melatonin-deficient mouse pineal glands. Phosphodiesterases are unlikely to suppress Aa-Nat induction because a phosphodiesterase inhibitor itself had no effect on the mRNA levels. Puromycin was ineffective in inducing Aa-Nat mRNA levels in either the presence or absence of isoproterenol, suggesting that newly synthesized proteins may not be necessary to gate the Aa-Nat responses. We also discovered circadian dependence of the expression of Period1-luminescence in Period1-luciferase transgenic mouse pineal glands: circadian clocks may be functional in culture. Aa-Nat mRNA levels showed no significant circadian rhythms in the absence of isoproterenol, thus suggesting that Aa-Nat mRNA levels are induced by adrenergic mechanisms, not by a pineal circadian clock. Our results suggest that the pineal circadian clock may determine timing when Aa-Nat gene expression can respond to inputs from the master circadian clock in the suprachiasmatic nucleus, e.g. adrenergic stimulation.

1-Methyl-3-isobutylxanthine↗

PubMed1981

Neuropeptides in the pineal gland? A critical immunocytochemical study.

In an attempt to localize components of the renin angiotensin-system in the pineal gland of rats, immunocytochemical studies using the PAP-technique were performed with antisera against angiotensin I, angiotensin II and angiotensinogen. The staining pattern thus obtained was not only the same for the three antisera, but was also identical to that shown for many other peptide-antisera in the literature. In those studies, the immunocytochemical staining had been ascribed to a distinct pineal cell population or to cell processes. However, by examining adjacent semithin and ultrathin sections by immunocytochemistry and electron microscopy, respectively, we could identify the extracellular perivascular compartment and its flocculent material as the site of staining. This unexpected localization and the observation of "immunoreactivity" of some preimmunesera in the same compartment as well as several additional findings and arguments are taken to suggest that likelihood of "pseudopositive" immunostaining, typical for the pineal gland.

Angiotensin I↗

PubMed2005

Fos-related antigen 2 (Fra-2) memorizes photoperiod in the rat pineal gland.

As the physiological role of fos-related antigen-2 (Fra-2) is largely unknown and since the pineal plays an important role in the photoperiodic control of the body, we have tested the hypothesis that Fra-2 expression is photoperiod-dependent and may be involved in imprinting photoperiod on the pineal gland and the body as a whole. To this end, we have investigated Fra-2 mRNA expression and Fra-2 protein expression under various light/dark (LD) cycles. A clear nocturnal increase occurs for both monitored parameters under all photoperiodic conditions studied. The level of Fra-2 protein expression clearly depends on photoperiod, because the amount of protein at dark onset and during the night negatively correlates with the length of the photoperiod. Further, high-phosphorylated Fra-2 isoforms are abundant under all photoperiods tested, with the exception of LD 20:4. Because Fra-2 phosphorylation depends on cGMP, a depressed cGMP response to adrenergic stimulation under LD 20:4 appears to explain this finding. We conclude that photoperiod is imprinted on Fra-2 in terms of both protein amount and protein phosphorylation in the rat pineal gland. This imprinting becomes fully manifest after about 7 days only, suggesting that a number of altered photoperiodic cycles are required for pineal Fra-2 to "learn" that the photoperiod has changed. Reportedly, Fra-2 limits expression of the enzyme iodothyronine deiodinase type II, which catalyzes the intracellular deiodination of thyroxine prohormone to the active 3,3',5-triiodothyronine. We have found that the extent of Fra-2 expression inversely correlates with the dII gene response to cAMP; hence the photoperiodic regulation of Fra-2 may affect the body by changing pineal thyroid hormone metabolism.

Acetyltransferases↗

PubMed1995

A bizarre receptor mediating stimulatory effect of histamine on cyclic AMP formation in duck pineal gland.

In agreement with our previous findings in chick pineal, histamine also appeared to be a potent stimulator of cAMP formation in intact duck pineal gland (about ten-fold increase above control at 100 microM), showing an EC50 value of 3-5 microM. The effect of histamine in the duck pineal was mimicked by several histaminergic drugs, with the following order of potency: histamine = 4-methylhistamine > 2-methylhistamine > R-alpha-methylhistamine > amthamine > 2-thiazolylethylamine = immepip > imetit > dimaprit. The effect of 100 microM histamine was unaffected by H1-, H2- and H3-receptor selective antagonists, mepyramine, ranitidine and thioperamide, respectively; yet, two other H2-antagonists, aminopotentidine and tiotidine, reduced the histamine effect by only 40%. Thus, these results, being in line with our previous chick data, give support to a suggestion that histamine may be considered a modulator of the pineal activity, and that the avian pineal may contain a novel or avian-specific histamine receptor modulating cAMP formation, whose pharmacology is different from that typical for H1-, H2-, or H3-type receptor.

Animals↗

PubMed1994

Immunocytochemical localization of basic fibroblast growth factor in the rat pineal gland.

The immunocytochemical localization of basic fibroblast growth factor (b-FGF) during the postnatal development of the rat pineal gland was studied using a polyclonal antibody against the fraction 1-24 of bovine recombinant b-FGF. Basic FGF immunoreactivity was evident from day 20 after birth in the endothelial cells and perivascular spaces of the gland. Although b-FGF immunostaining showed its maximal expression at 30-45 days, it was maintained throughout the entire study period (up to 6 months), mainly in the distal zone of the gland. Pinealocytes did not show b-FGF immunoreactivity at any time. There were no differences in the localization patterns or the intensity of b-FGF immunostaining after the prenatal denervation with DSP-4, a neurotoxic amine. The physiological role of b-FGF in the adult pineal gland remains unknown; however, it does not seem to play a major role during the cytodifferentiation period of the parenchymal cells, or during the neovascularization in the early postnatal days. Furthermore, its immunocytochemical expression is not affected by the prenatal sympathetic denervation with DSP-4, in contrast with other neurotropic factors.

Animals↗

PubMedDate not supplied

NGF expression in the aged rat pineal gland does not correlate with loss of sympathetic axonal branches and varicosities.

The factors that determine the ability of some, but not all neurons, to sustain their axonal projections during aging remain largely unknown. Because sympathetic neurons remain responsive to nerve growth factor (NGF) in old age, it has been proposed that the selective decrease observed in the sympathetic innervation to some targets in aged rats may be the result of a deficit in target-derived NGF. In this study we utilized two different techniques to demonstrate decreased target innervation by sympathetic fibers in the aged rat pineal gland, which is an appropriate and relevant model for examining mechanisms of neuron-target interactions in aging. Tyrosine hydroxylase immunoreactive profiles were quantified in pineal glands of young and aged male Sprague-Dawley rats. The density of tyrosine hydroxylase-immunoreactive fibers was 30% lower in aged pineals, although the remaining fibers contained 20% more tyrosine hydroxylase-immunoreactivity. Othograde tracing of the pineal sympathetic innervation using biotinylated dextran revealed that average axon length, varicosity numbers, branch point numbers, and numbers of terminations were all decreased by approximately 50% in aged tissues, indicating possible functional deficits. These findings suggest that whole branches, along with their associated varicosities were lost in old age. A sensitive quantitative ribonuclease protection assay and a two-site ELISA assay were used to examine whether reduced NGF availability might correlate with sympathetic nerve atrophy. No significant differences were detected in either NGF mRNA or NGF protein levels when comparing young and aged pineal glands, suggesting that atrophy in aged sympathetic neurons is not causally related to reduced availability of NGF at the target. Our results indicate that mechanisms other than NGF expression need to be explored in order to explain the age-related axonal regression observed in this target.

Aging↗

PubMed2006

Cyclic AMP-inducible genes respond uniformly to seasonal lighting conditions in the rat pineal gland.

The encoding of photoperiodic information ensues in terms of the daily profile in the expression of cyclic AMP (cAMP)-inducible genes such as the arylalkylamine N-acetyltransferase (AA-NAT) gene that encodes the rate-limiting enzyme in melatonin formation. In the present study, we compared the influence of the photoperiodic history on the cAMP-inducible genes AA-NAT, inducible cyclic AMP early repressor (ICER), fos-related antigen-2 (FRA-2), mitogen-activated protein kinase phosphatase-1 (MKP-1), nerve growth factor inducible gene-A (NGFI-A) and nerve growth factor inducible gene-B (NGFI-B) in the pineal gland of rats. For this purpose, we monitored the daily profiles of each gene in the same pineal gland under a long (light/dark 16:8) and a short (light/dark 8:16) photoperiod by measuring the respective mRNA amounts by real-time polymerase chain reaction analysis. We found that, for all genes under investigation, the duration of increased nocturnal expression is lengthened and, in relation to light onset, the nocturnal rise is earlier under the long photoperiod (light/dark 16:8). Furthermore, with the exception of ICER, all other cAMP-inducible genes tend to display higher maximum expression under light/dark 8:16 than under light/dark 16:8. Photoperiod-dependent changes persist for all of the cAMP-inducible genes when the rats are kept for two cycles under constant darkness. Therefore, all cAMP-inducible genes are also influenced by the photoperiod of prior entrained cycles. Our study indicates that, despite differences regarding the expressional control and the temporal phasing of the daily profile, cAMP-inducible genes are uniformly influenced by photoperiodic history in the rat pineal gland.

Animals↗

PubMed1990

Chronopharmacological actions of the pineal gland.

In all mammalian species studied to date, the pineal gland shows a pronounced circadian rhythm with high activity at night and very low activity in daytime, as reflected in the output of its hormone, melatonin. The pineal is one of the few organs which can synthesize melatonin and, under normal circumstances, is virtually the only source of circulating melatonin. Pineal activity is tightly controlled by the light/dark cycle, in such a manner that melatonin can convey information to the organism on the length of the dark phase of the photoperiod. In seasonal breeding species, the 24 hour pattern of secretion of melatonin shows seasonal changes which are crucial for determining the timing of seasonal changes in bodily function. In man, alterations in pineal function are of significance in jet-lag, shift work and in affective disorder.

Aging↗

PubMed2006

Chronic stress decreases the expression of sympathetic markers in the pineal gland and increases plasma melatonin concentration in rats.

Chronic stress affects brain areas involved in learning and emotional responses. Although most studies have concentrated on the effect of stress on limbic-related brain structures, in this study we investigated whether chronic stress might induce impairments in diencephalic structures associated with limbic components of the stress response. Specifically, we analyzed the effect of chronic immobilization stress on the expression of sympathetic markers in the rat epithalamic pineal gland by immunohistochemistry and western blot, whereas the plasma melatonin concentration was determined by radioimmunoassay. We found that chronic stress decreased the expression of three sympathetic markers in the pineal gland, tyrosine hydroxylase, the p75 neurotrophin receptor and alpha-tubulin, while the same treatment did not affect the expression of the non-specific sympathetic markers Erk1 and Erk2, and glyceraldehyde-3-phosphate dehydrogenase. Furthermore, these results were correlated with a significant increase in plasma melatonin concentration in stressed rats when compared with control animals. Our findings indicate that stress may impair pineal sympathetic inputs, leading to an abnormal melatonin release that may contribute to environmental maladaptation. In addition, we propose that the pineal gland is a target of glucocorticoid damage during stress.

Animals↗

PubMed1992

Biphasic 24-hour variations in cyclic GMP accumulation in the rat pineal gland are due to corresponding changes in the activity of cytosolic and particulate guanylate cyclase.

Various parameters of the rat pineal gland display a 24-h rhythm. However, nothing is known about possible 24-h variations in cyclic GMP (cGMP) metabolism. In the present study, 24-h variations in pineal gland cGMP accumulation were investigated by determining the increase in cGMP level with and without inhibitors of phosphodiesterase at different time points over a light/dark cycle (12/12 h). Furthermore, the activity of guanylate cyclase (GC) was determined under substrate-saturated conditions regarding the cytosolic and particulate forms of the enzyme. It has been found that cGMP accumulation and GC activity display biphasic 24-h variations with two peaks--one approximately 7 h after lights "on" and the other approximately 7 h after lights "off." The activity of cytosolic GC remains unchanged in the presence of the nitric oxide (NO) synthesis inhibitor N-monomethyl-L-arginine, indicating that 24-h variations in the activity do not reflect changes in the synthesis of the GC stimulator NO.

Animals↗

PubMed1994

Day-night variations in melatonin secretion by the pineal gland during febrile and epileptic convulsions in children.

The pineal gland is a complex neuroendocrine organ with pronounced effects on central nervous system activity. Because previous studies in animals and humans have suggested an anticonvulsant role for the pineal hormone melatonin, we studied the day-night variations in plasma melatonin in normal children and children with febrile or epileptic convulsions. We found significant changes in day-night melatonin levels during convulsions, consistent with the hypothesis that melatonin has an inhibitory function on central nervous system activity.

Brain↗

PubMed1984

Trophic response of hamster brown adipose tissue: roles of norepinephrine and pineal gland.

The objective was to find out whether the reduced amount of brown adipose tissue in myopathic hamsters [Am. J. Physiol. 239 (Cell Physiol. 8): C18-C22, 1980] was secondary to a refractoriness to the trophic influence of norepinephrine. However, no evidence for any trophic influence of norepinephrine on brown adipose tissue of either normal or myopathic hamsters could be detected under experimental conditions that have demonstrated such an influence in rats. A mediator other than norepinephrine, melatonin, secreted by the pineal gland, is known to mediate the control of brown adipose tissue growth induced in hamsters by short photoperiod. Further studies of intact or pinealectomized hamsters showed that the pineal gland was not required for either cold- or diet-induced growth of brown adipose tissue. It is concluded that the defect in control of brown adipose tissue size in the hamster with muscular dystrophy is not due either to abnormal control by norepinephrine or to the pineal gland since neither of these appears to participate in the normal regulation of brown adipose tissue size in relation to environmental temperature or to diet.

Acclimatization↗

PubMed1980

Hydroxyindole-O-methyltransferase (HIOMT), catechol-O-methyltransferase (COMT) and histamine-N-methyltransferase (HNMT) in the pineal gland of the vizcacha (Lagostomus maximus maximus).

The activities of three methylating enzymes HIOMT, COMT, and HNMT were determined in pineal glands from 2 groups of adult vizcachas of both sexes, one (I) maintained under permanent lighting (15 days) and the other (II) kept in darkness. The control determinations (III) were carried out in pineal glands from animals hunted and killed during the night. In (I) the HIOMT activity decreased and the COMT activity increased; no changes were exhibited by HNMT. In (II) showed a diminished HIOMT activity. In captivity illumination affected HIOMT and COMT activites in a similar form to that observed in other species of rodents. The decrease in HIOMT activity in (II) suggests that captivity may affect pineal function, possibly as a consequence of a decrease in locomotor activity.

Acetylserotonin O-Methyltransferase↗

PubMed1987

Innervation of the pineal gland in the rat: an HRP study.

Injections of horseradish peroxidase were made stereotaxically and directly (surgically exposed) into the pineal gland of Sprague-Dawley and Long-Evans rats weighing 30 to 500 g (20 to 130 days of age). Retrogradely labeled cells were seen in the superior cervical ganglia. Anterogradely labeled fibers were observed within the pineal stalk, lamina intercalaris, and the medial habenular nuclei. Terminal fields were identified in lamina intercalaris and medial habenular nuclei. Labeled cells were not seen within the central nervous system. These results suggest that in the rat the pineal gland is not centrally innervated but in fact is innervated solely by the sympathetic postganglionic fibers.

Animals↗

PubMed1984

Concurrent determination of enzymatic activities and substrate concentrations in the melatonin synthetic pathway within the same rat pineal gland.

This study details the procedures involved in measuring a number of the componets of indole metabolism within the pineal gland. Tryptophan, 5-hydroxytryptophan, serotonin, N-acetylserotonin, melatonin, 5-hydroxyindoleacetic acid, N-acetyltransferase (NAT) activity, and hydroxyindole-O-methyltransferase activity were measured by a combination of three techniques, which included microassays, radioimmunoassay, and high-performance liquid chromatography. Determination of the melatonin synthetic pathway components within the same gland reduces the number of animals needed for studies and allows correlations between these constituents to be calculated. Very high degrees of correlation (r = 0.91-0.99) are seen between those compounds which exhibit significant rhythms (serotonin, NAT activity, N-acetylserotonin, and melatonin) when group means are compared. When correlations are calculated on a per-animal basis throughout the experiment, moderate to high degrees of correlation (r = 0.57-0.79) are found among those components that exhibit rhythms. However, when correlations are determined on a per-animal basis at each time point, no significant correlations are found. One hypothesis accounting for these differences may be that changes occur in indole metabolism within the same pineal gland over a period of a few minutes.

Acetyltransferases↗

PubMed1991

Day and nighttime concentrations of 5-methoxytryptophol and melatonin in the retina and pineal gland from different classes of vertebrates.

5-Methoxytryptophol (ML) and melatonin concentrations were determined by radioimmunoassay in the retinae and pineal glands of frogs (Rana esculenta), chickens (Gallus domesticus), quails (Coturnix coturnix), and European hamsters (Cricetus cricetus), killed in the afternoon (1500-1700 hr) and around midnight (2400-0200 hr). ML was only detectable in significant amounts in the frog retina. In the pineal gland ML levels showed the opposite profile to retinal ML, with measurable levels in the chicken, quail, and hamster and undetectable levels in the frog (less than 2.0 pg/gland). A significant day/night variation was observed in the bird pineal only, with higher levels occurring during the day. In contrast to ML, the interspecies variation in melatonin content was similar in the retina and pineal, with the highest concentrations occurring in the chicken greater than quail much greater than frog greater than hamster. Significantly higher night levels of melatonin were observed in the retina of the chicken and quail and in the pineal of the chicken, quail, and frog. The ratio of ML:melatonin concentrations in the retina and pineal also showed interspecies variations. In the birds the amount of ML was minimal in comparison with the amount of melatonin (1-4% retina; 0.3-12% pineal). The highest ML:melatonin occurred in the retina of the frog and in the pineal of the European hamster.

Animals↗

PubMed1988

Symptomatic glial cysts of the pineal gland.

Two cases of symptomatic glial cysts of the pineal gland are reported. An origin similar to that proposed for paraventricular glial cysts of the brain is accepted. These unusual lesions could be considered in the differential diagnosis of cystic pineal masses.

Adult↗