SEARCH · Search PubMed

Results for “PINEAL GLAND”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

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

At least 1,027 records · Page 57Linked to original sources

PubMed1995

In the rat pineal gland, but not in the suprachiasmatic nucleus, the amount of constitutive neuronal nitric oxide synthase is regulated by environmental lighting conditions.

To investigate whether the expression of neuronal isoform of nitric oxide synthase is photoneurally regulated, we examined the amount of the enzyme by means of Western Blot analysis under different environmental lighting conditions in two photoneuronally regulated tissues, the pineal gland and the suprachiasmatic nucleus of the rat. In the pineal gland nitric oxide synthase immunoreactivity was strikingly decreased when rats had been exposed for 8 days to light:dark 20:4 conditions or to constant light. The decline in nitric oxide synthase immunoreactivity following LL reversed after 4 days under light:dark 12:12. We conclude that in the rat pineal the amount of neuronal nitric oxide synthase is controlled by environmental lighting conditions. That it is not justified to extrapolate from the pineal to other photoneuronally regulated centers is illustrated by the present finding that the suprachiasmatic nucleus did not reveal changes in the amount of neuronal nitric oxide synthase.

Amino Acid Oxidoreductases↗

PubMed1997

No short-term effects of high-frequency electromagnetic fields on the mammalian pineal gland.

There is ample experimental evidence that changes of earth-strength static magnetic fields, pulsed magnetic fields, or alternating electric fields (60 Hz) depress the nocturnally enhanced melatonin synthesis of the pineal gland of certain mammals. No data on the effects of high-frequency electromagnetic fields on melatonin synthesis is available. In the present study, exposure to 900 MHz electromagnetic fields [0.1 to 0.6 mW/cm2, approximately 0.06 to 0.36 W/kg specific absorption rate (SAR) in rats and 0.04 W/kg in Djungarian hamsters; both continuous and/or pulsed at 217 Hz, for 15 min to 6 h] at day or night had no notable short-term effect on pineal melatonin synthesis in male and female Sprague-Dawley rats and Djungarian hamsters. Pineal synaptic ribbon profile numbers (studied in rats only) were likewise not affected. The 900 MHz electromagnetic fields, unpulsed or pulsed at 217 Hz, as applied in the present study, have no short-term effect on the mammalian pineal gland.

Animals↗

PubMed1986

Antidepressants and protein kinases: desipramine treatment affects pineal gland cAMP-dependent protein kinase activity.

To further describe the molecular mechanisms involved in reductions in noradrenergic responsiveness induced by antidepressants, the effects of antidepressant treatment on the rat pineal gland cAMP-dependent protein kinase system were examined. The concentration of cyclic AMP-dependent protein kinase activity was reduced 24 h after acute treatment with desipramine, as well as in animals treated repeatedly with desipramine. Assays performed in the presence of cAMP protein kinase inhibitor showed no significant effects of either acute or repeated desipramine treatment on the concentration of cAMP-independent protein kinase activity. Neither acute nor repeated treatment with other antidepressants (zimelidine, iprindole or fluoxetine) significantly altered the concentration of cAMP-dependent or cAMP-independent protein kinase activity. Using activity ratios to judge the extent of activation of cAMP-dependent protein kinase in vivo, it was found that isoproterenol-induced increases in cAMP protein kinase activity were similar in control and acutely-treated animals, but were reduced with repeated desipramine treatment. The extent of protein kinase activation was also elevated by both acute and repeated treatment in the absence of isoproterenol. In further studies, desipramine (10 microM) did not directly affect activation of the kinase by cAMP or maximum kinase catalytic activity. These results show that the concentration and extent of activation of cAMP protein kinase is altered following desipramine treatment in the rat pineal gland and that modulation of cAMP protein kinase may be a locus of regulation for desipramine-mediated reduction in noradrenergic responsiveness.

Animals↗

PubMed1983

Catecholamines and phenylethanolamine N-methyltransferase in selected brain nuclei and in the pineal gland of neurogenically hypertensive rats.

Catecholamines (dopamine, norepinephrine and epinephrine) and the epinephrine-forming enzyme, phenylethanolamine N-methyltransferase (PNMT, E.C. 2.1.1.28) were measured in selective brainstem and hypothalamic nuclei and in the pineal gland of acutely (3 days after operation) and chronically (2 weeks after operation) neurogenically hypertensive (sinoaortically denervated, SAD) rats. Alterations in catecholamine levels and in PNMT activity were restricted to a few brain nuclei and the pineal gland, and were dependent on the time elapsed since SAD. Our results suggest a participation of discrete hypothalamic norepinephrine and brainstem epinephrine neurons in the development and maintenance of neurogenic hypertension.

Animals↗

PubMed1991

Immunohistochemical localization of serotonin in the pineal gland of the chicken during post-hatching development in relation to light-dark cycle.

In the present immunohistochemical study using an antiserum against serotonin, the localization of serotonin was demonstrated in the pineal gland of the chickens from 1 day to 3 years of age. Serotonin-like immunoreactivity was located in the supranuclear region of the follicular cells and in the perikaryon of the parafollicular cells in the pineal gland, exhibiting distinct changes during post-hatching development. The reactivity reached its peak in 1-year-old chicken. Moreover, diurnal changes in immunoreactivity also existed after 1 day of age, being high in the light period and low in the dark period. Occasionally in 1-3-year-old chickens, a part of granular-shaped reactive products observed in the light period appear to be diffused in the cytoplasm in the dark period. In addition, a number of immunoreactive fibers were shown in the pineal parenchyma, exhibiting a slight increase in number and in reactivity at 40 days of age.

Aging↗

PubMed1999

Role of photoperiod and the pineal gland in T cell-dependent humoral immune reactivity in the Siberian hamster.

The present study tested the hypothesis that antibody production in response to xenoantigen is modulated by daylength and dependent upon the pineal gland. Alter injection of sheep erythrocytes (SRBC), serum immunoglobulin (Ig) concentrations were 5-fold lower in hamsters in short versus long days. Pinealectomy (Pinx) abolished the nocturnal melatonin rhythm, blocked short-day-mediated testis regression, and eliminated the short-day reduction in Ig production after SRBC treatment. Antibody titers in response to SRBC were equivalently augmented in short-day Pinx and long-day sham hamsters. The results indicate that photoperiodic effects on T cell-dependent humoral immunity are dependent upon the pineal gland. These findings raise the possibility that day length-associated changes in some immune system functions are mediated by the pineal melatonin rhythm.

Animals↗

PubMed1989

Photoperiodic modulation of sexual and aggressive behavior in female golden hamsters (Mesocricetus auratus): role of the pineal gland.

Pinealectomized female hamsters (Mesocricetus auratus) housed in a short-day photoperiod were ovariectomized and tested for hormone-induced sexual receptivity in order to investigate the role of the pineal gland in the control of behavioral sensitivity to exogenous ovarian steroid hormones (Experiment 1). Behavioral sensitivity to hormones was further investigated in females maintained in a long-day photoperiod and rendered acyclic by daily administration of exogenous melatonin (Experiment 2). Female aggressive behavior was also monitored in all tests. Pinealectomy did not affect the reduced behavioral sensitivity to exogenous estrogen (E) induced by short days. These animals were also partially refractory to the effects of E when combined with low doses of progesterone. In addition, although melatonin administration mimicked the effects of short days on estrous cyclicity, the expression of hormone-dependent behaviors in these animals resembled the pattern displayed by control animals kept in long days. Thus, these findings suggest that the pineal gland plays a negligible role in the photoperiodic modulation of hormone-dependent sociosexual behaviors in female hamsters.

Aggression↗

PubMed2001

Photoreception and circadian clock system of the chicken pineal gland.

Chicken pinealocytes contain three major components of the circadian clock system: 1) a self-sustained oscillator, 2) a photic-input pathway to the oscillator, and 3) an overt output represented by the rhythmic production of melatonin. Even under cultured conditions of isolated pineal gland or dissociated pinealocytes, the input-oscillator-output functions are well maintained. Because of these experimental advantages, chicken pineal gland has been one of the best models for the study of the circadian clock system. Since the finding of a pineal-specific photoreceptive molecule, pinopsin, we have characterized the endogenous phototransduction pathway in the pinealocytes. On the other hand, despite the long history of chick pineal research, the molecular mechanism underlying the pineal clock oscillation has been largely unknown. Our recent characterization of the chick pineal clock genes strongly suggests that they constitute a transcription/translation-based autoregulatory feedback loop, which is very similar to that generating circadian rhythmicity in mammalian SCN.

Animals↗

PubMed1983

Influence of the pineal gland on hypothalamic content of TRH in the Syrian hamster.

Blinding adult female hamsters by bilateral orbital enucleation caused an increase in thyrotropin-releasing hormone (TRH) content of the medial basal hypothalamus and also led to an increase in TRH content in the remainder of the hypothalamus (dorsal hypothalamus). Although pinealectomy by itself had no significant effect on the neuroendocrine-thyroid axis, this surgical procedure prevented the inhibition of serum thyroxin observed in blinded hamsters. Pinealectomy also prevented the increase in TRH content of medial basal and dorsal hypothalamus observed in blinded hamsters. The results are consistent with the view that the pineal gland has a CNS site of action and provide evidence that the anti-thyroid influence of the pineal gland can be explained by pineal inhibition of TRH release.

Animals↗

PubMed1978

Post-hatching evolution of the pineal gland of the chicken.

The authors studied the evolution of the pineal gland of the chicken (Gallus gallus) from hatching until 34 months of age. They describe the progressive decrease of the follicular cavities and the appearance of solid-looking cavities. The stroma increases with age, dividing the pineal parenchyma into territories of small caliber.

Age Factors↗

PubMed1998

N-3 fatty acid deficiency in the rat pineal gland: effects on phospholipid molecular species composition and endogenous levels of melatonin and lipoxygenase products.

N-3 essential fatty acid deficiency affects a number of biological and physiological processes. In this study, we investigated the effect of n-3 essential fatty acid status on two key pineal biochemical functions, melatonin production and lipoxygenation, using pineal glands from rats given an n-3-adequate or n-3-deficient diet. The pineal total lipid profile and phospholipid molecular species distribution altered by n-3 deficiency were evaluated in parallel. In pineal glands from n-3-deficient rats, an 87% reduction of 22:6n-3 (docosahexaenoic acid) was observed, and this decrease was accompanied by increases in 22:4n-6 (docosatetraenoic acid, 3-fold), 22:5n-6 (docosapentaenoic acid, 12-fold), and 20:4n-6 (arachidonic acid, 48%). The significant decrease of 22:6n-3 containing species in phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) was also evident. These decreases in 22:6n-3 containing PL species were compensated by substantial accumulations of 22:4n-6 or 22:5n-6 and slight increases in 20:4n-6 containing PL species in PC and PE. In PS, however, the accumulation of n-6 species was not adequate to compensate for the loss of 22:6n-3 species. N-3 deficiency significantly reduced non-esterified 20:4n-6 and 22:6n-3 levels in pineals (25% and 65%, respectively). Concomitantly, the endogenous 12-HETE level decreased by 35% in deficient pineals. In contrast, n-3 deficiency led to a more than 60% increase in the daytime pineal melatonin level. In conclusion, n-3 fatty acid deficiency not only has profound effects on pineal lipid profiles but also on pineal biochemical activities. These results suggest that n-3 fatty acids may play a critical role in regulating pineal function.

Animals↗

PubMed1990

Characterization of A-2 receptors in postmortem human pineal gland.

We have examined the binding of the adenosine agonist radioligands [3N]N6-cyclohexyladenosine ([3H]CHA) and [3H]5'-N-ethylcarboxamidoadenosine ([3H]NECA) to membranes prepared from postmortem human pineal glands. The results showed that the A-1-specific ligand CHA did not bind to membranes. By contrast, [3H]NECA, a nonselective A-1/A-2 ligand, gave 68% specific binding of the total binding. This specific binding was nearly insensitive to the N-ethyl-maleimide pretreatment method. To characterize this binding, we used cyclopentyladenosine (50 nM). Under those conditions [3H]NECA binding at 30 degrees C was rapid and reversible; the KD determined from the kinetic studies was 141 nM. In postmortem human pineal gland, the rank order of potency of adenosine analogues and drugs competing with [3H]NECA showed the specificity for an A-2 receptor: NECA greater than 2-chloroadenosine greater than L-N6(2-phenylisopropyl)adenosine greater than 8-phenyltheophylline greater than 3-isobutyl-1-methylxanthine greater than caffeine. Guanylylimidodiphosphate (100 microM) induced a decrease in the affinity of [3H]NECA, a result suggesting the involvement of a G protein mechanism in the coupling of the adenosine receptor to other components of the receptor complex. Scatchard analysis revealed one class of binding sites for [3H]NECA with KD and Bmax ranging from 175 to 268 nM and 11.0 to 14.1 pmol/mg protein, respectively. The binding of [3H]NECA was not affected by age, sex, or postmortem delay. [3H]NECA should be a useful tool to assess brain A-2 receptor density in a variety of neuropsychiatric disorders.

Adenosine↗

PubMed1989

Ultrastructural study of the distribution of calcium in the pineal gland of the rat subjected to manipulation of the photoperiod.

Using the pyroantimoniate technique, a study was conducted at electron microscope level on the distribution of the calcium ion in the pineal glands of normal adult Sprague-Dawley rats with initial weights of 150-200 g subjected to a 12:12 light dark cycle and others under the same conditions were subjected to modifications in the noradrenergic signal, such as continuous illumination over 7 days, blinding by bilateral enucleation (7 or 90 days) before sacrifice and bilateral superior cervical gangliectomy at 21 days before sacrifice. All the animals were sacrificed by decapitation, half of them at midday and the other half at midnight. Abundant fine precipitations of calcium were found in the intercellular spaces of the pineal glands of the normal rats. By contrast, in the gangliectomized animals subjected to constant illumination and chronic binding these precipitations were few in number. Additionally, two types of pinealocytes were observed regarding the distribution and concentration of intracytoplasmic calcium in both the normal and experimentally manipulated animals. Type I correspond to the classic light pinealocytes, with an absence of intracytoplasmic precipitations, although in the normal and gangliectomized animals sacrificed at midnight it was possible to observe fine deposits inside the mitochondrial matrix. Type II correspond to the classic dark pinealocytes, with a dense cytoplasmic matrix and numerous deposits of intracytoplasmic and intranuclear calcium; these were never seen in the type I pinealocytes.

Adrenergic Fibers↗

PubMed1997

Immunohistochemical localization of gonadotropin and gonadal steroid receptors in human pineal glands.

Recently, we demonstrated that melatonin secretion was increased in male patients with GnRH deficiency and decreased to normal levels during testosterone treatment. These data suggested that gonadal steroids modulate melatonin secretion, probably by activating specific receptors in the pineal gland. We used immunohistochemistry to localize gonadotropin (LH and FSH) and gonadal steroid (androgens and estrogens) receptors in human pineal glands. Tissues were obtained at autopsy from 25 males, aged 19-87 yr, and five prepubertal children, aged 0.2-10 yr. Positive staining for all four types of receptors (LH, FSH, androgen, and estrogen) in the pineal parenchymal cells, pinealocytes, was evident in all 30 glands examined. Double staining revealed that nuclear receptors (androgen or estrogen) co-existed with cytoplasmatic receptors (LH or FSH) in the same cells. The results demonstrate the presence of gonadotropin and gonadal steroid receptors in human pinealocytes from infancy to old age.

Adult↗

PubMed1994

The presence of opioidergic pinealocytes in the pineal gland of the European hamster (Cricetus cricetus): an immunocytochemical study.

By use of antibodies raised against leu-enkephalin and met-enkephalin immunoreactive, opioidergic bi- and multipolar cells were demonstrated in the pineal gland of the European hamster. Ultrastructural analysis of these opioidergic cells revealed them to be pinealocytes. Processes emerged from the cell bodies and terminated in club-shaped swellings containing many small clear and some larger granular vesicles. Some of the terminals made synapse-like contacts with non-immunoreactive pinealocytes. The presence of the opioidergic pinealocytes strongly indicates that the pineal gland of the European hamster, in addition to its pinealopetal nervous regulation, is regulated by intrapineal peptidergic pinealocytes via a synaptic mechanism. A possible paracrine role of the opioidergic cells must also be considered.

Animals↗

PubMedDate not supplied

Effects of calcium ions and substances affecting Ca2+ -related mechanisms on histamine-evoked stimulation of cyclic AMP formation in chick pineal gland.

In avian central nervous system (CNS), and particularly in the pineal gland, histamine (HA) potently stimulates synthesis of cyclic AMP in intact tissue, and only weakly affects adenylyl cyclase activity in membrane preparation. In this work, we focussed on calcium (Ca2+) as a possible link in the mechanism through which HA affects cyclic AMP generation in the chick pineal. The problem was studied in two sets of experiments where the action of HA on the pineal cyclic AMP was tested: (1) in the incubation medium containing various compounds influencing Ca2+ influx and/or Ca2+ intracellular concentration/action (Ca2+ -ionophore calcimycin, Ca2+ -channel agonist Bay-K 8644, Ca2+ -channels blockers: diltiazem, verapamil, nifedipine and omega-conotoxin-GVIA, CaCl2, EGTA in the absence of CaCl2 in the incubation medium, as well as calmodulin inhibitors: calmidazolium and W-7), and (2) in a CaCl2-free incubation medium yet containing different concentrations of BaCl2, CdCl2, CoCl2, MgCl2, and NiSO4. The results of the first series were mostly negative; an exception was the inhibiton of the HA-evoked cyclic AMP formation observed in the presence of 5.2 and 10.4 mM CaCl2 In the second series of experiments, divalent cations (however with the exception of Mg2+, which was inactive at concentrations up to 15.6 mM) inhibited the HA-evoked cyclic AMP production, with the following rank order of potency: Cd2+ >> Co2+ >> Ni2+ > Ba2+. The inhibitory effect of CdCl2 was prevented by nifedipine. Taken together, the present data suggest that intracellular Ca2+ -related mechanisms are not of major importance in the HA action on cyclic AMP synthesis in the chick pineal. It could be suspected that the inhibition of the HA-driven cyclic AMP formation by high concentrations of Ca2+, and other divalent cations, probably resulted from their direct inhibitory interaction with the catalytic site of the pineal adenylyl cyclase.

Animals↗

PubMed1976

Seasonal changes in the pineal gland related to the reproductive cycle in the male hare, Lepus europaeus.

During the autumn months, the gonads and reproductive tract of adult male hares (Lepus europaeus) are regressed and circulating gonadotrophin levels are low. At this time the pineal glands are most active as judged by the organ size, and the nuclear and cytoplasmic size of the pinealocytes. There was an inverse relationship between the size of the pineal gland and the weight of the testis, the plasma and testicular testosterone levels, and possibly also the plasma LH levels.

Animals↗

PubMed1988

Day-night rhythm of 5-methoxytryptamine biosynthesis in the pineal gland of the golden hamster (Mesocricetus auratus).

5-Methoxytryptamine is a potent agonist of presynaptic 5-hydroxytryptamine autoreceptors modulating serotonin release in the central nervous system. This methoxyindole can be synthesized in the pineal gland, but its presence in vivo is still controversial, probably because of rapid catabolism by monoamine oxidase. An improved high-pressure liquid chromatography method, with coulometric detection, has been developed for the simultaneous measurement of melatonin, 5-methoxytryptamine, 5-methoxytryptophol and 5-methoxyindolacetic acid. We have demonstrated a day-night rhythmicity in the amount of 5-methoxytryptamine in the pineal gland of golden hamsters (Mesocricetus auratus) maintained under a long photoperiod (14 h light: 10 h darkness) and pretreated with the monoamine oxidase inhibitor pargyline. Levels of 5-methoxytryptamine were highest at 16.30 h and lowest at 00.30 h. The rhythm for 5-methoxytryptamine appears to be the same as for serotonin (opposite in phase to that of melatonin). The identification of 5-methoxytryptamine has been confirmed by analysis with gas chromatography-mass spectrometry.

5-Methoxytryptamine↗