Showing papers on "Pinealocyte published in 1994"

Melatonin and the Mammalian Pineal Gland

Abstract: Foreword. Melatonin and the mammalian pineal gland. Structure of the pineal gland. Biochemistry of the pineal. Light-dark control of melatonin synthesis. Physiology of the pineal: role in photoperiodic seasonal functions. Role of the pineal gland and melatonin in circadian rhythms. The pineal in human physiology and pathology. Effects of melatonin: therapeutic potential and significance to human health. Target sites and mechanism of action of melatonin. Index.

Pinopsin is a chicken pineal photoreceptive molecule

Abstract: In avian pinealocytes, an environmental light signal resets the phase of the endogenous circadian pacemaker that controls the rhythmic production of melatonin. Investigation of the pineal phototransduction pathway should therefore reveal the molecular mechanism of the biological clock. The presence of rhodopsin-like photoreceptive pigment, transducin-like immunoreaction, and cyclic GMP-dependent cation-channel activity in the avian pinealocytes suggests that there is a similarity between retinal rod cells and pinealocytes in the phototransduction pathway. We have now cloned chicken pineal cDNA encoding the photoreceptive molecule, which is 43-48% identical in amino-acid sequence to vertebrate retinal opsins. Pineal opsin, produced by transfection of complementary DNA into cultured cells, was reconstituted with 11-cis-retinal, resulting in formation of a blue-sensitive pigment (lambda max approximately 470 nm). In the light of this functional evidence and because the gene is specifically expressed only in the pineal gland, we conclude that it is a pineal photosensor and name it pinopsin.

The Pineal Organ as a Component of the Biological Clock.

Abstract: In conclusion, several trends are observed in regard to the phylogenetic development of the pineal organ, which are relevant for our understanding of the evolution of biological clock mechanisms. 1. The pineal organ of all vertebrates investigated thus far is capable of producing and releasing melatonin. Melatonin is rhythmically produced and released during darkness and, thus, represents an important neuroendocrine information on the ambient photoperiod. 2. The rhythmic production of melatonin is under control of endogenous oscillators and photoreceptor cells. In several nonmammalian species, these endogenous oscillators and photoreceptors are located within the pineal organ itself. In some avian species, the inherent rhythmicity of the pineal organ appears to be influenced by pacemakers located in other parts of the central nervous system. Their information may be transmitted to the pineal organ via the sympathetic innervation. This innervation develops progressively in the course of phylogeny. In mammals certain pinealocytes express proteins which are specific of retinal and pineal photoreceptors, but these proteins are obviously not involved in photoreception and phototransduction. The mammalian pineal organ lacks not only functioning photoreceptors, but also endogenous oscillators. The photoreceptor cells involved in regulation of the melatonin biosynthesis are located in the retina; the major endogenous oscillator is the suprachiasmatic nucleus (SCN) of the hypothalamus. Information from the retina and the SCN is transmitted to the mammalian pineal organ via a complex neuronal chain, whose last member is the sympathetic innervation originating from the superior cervical ganglion. This innervation is mandatory to maintain the rhythm of the melatonin biosynthesis in the mammalian pineal organ. Interestingly, the effects of noradrenaline, the major neurotransmitter in the sympathetic nerve fibers, displays opposite effects on the melatonin biosynthesis in birds and mammals: it stimulates the melatonin biosynthesis in the mammalian pineal organ, but inhibits the melatonin formation in the chicken. This conversion occurs at the level of the adrenoreceptors. 3. The intrapineal nerve cells giving rise to pinealofugal neuronal projections are reduced in the course of phylogeny. Nevertheless, direct neuronlike connections appear to exist between the pineal organ and the central nervous system of mammals. These projections originate from a population of pinealocytes. Whether such projections are involved in biological clock mechanisms remains an issue not yet resolved. The ontogenetic data reviewed support the notion that, in lower vertebrates, melatonin biosynthesis is primarily controlled by intrapineal photoreceptors, whereas, in mammals, it depends on retinal photoreceptors and the sympathetic innervation of the pineal.(ABSTRACT TRUNCATED AT 400 WORDS)

Structural and ultrastructural characteristics of human pineal gland, and pineal parenchymal tumors

Abstract: We have studied 20 pineal parenchymal tumors (PPT) and 4 normal or cystic pineal glands both by light and electron microscopy and immunohistochemistry with antibodies against glial markers [glial fibrillary acidic protein (GFAP) and protein S-100] or neural/neuroendocrine markers [neurofilaments (NF), synaptophysin and chromogranin A]. Light microscopy revealed the cellular organization of pinealocytes in the normal gland and in different morphological types of pineal tumors (typical pineocytomas, PPT with intermediate differentiation, mixed PPT exhibiting elements of both pineocytoma and pineoblastoma and pineoblastomas). Immunohistochemistry showed the presence of GFAP and protein S-100 in interstitial cells in nonneoplastic pineal gland. Cell processes were labeled with anti-synaptophysin and anti-NF antibodies. No immunoreactivity was found for chromogranin A in non-neoplastic pineal gland. In pineocytomas, GFAP and protein S-100 were observed in interstitial cells. Synaptophysin and NF were present in the large rosettes of pineocytomas. Synaptophysin, NF and chromogranin A were present in pineocytomas with a lobular arrangement of cells. Anti-chromogranin A immuno-reactivity was also seen in lobular areas of some PPT with intermediate differentiation. Analysis of normal human pineal gland by electron microscopy showed the presence of vesicle-crowned rodlets (VCR or synaptic ribbons), fibrous filaments (F), paired twisted filaments but few dense-core vesicles (DCV) in normal pinealocytes. Tumoral pineal cells appeared to differentiate either towards a neurosensory pathway characterized by the presence of sensory cells elements (VCR and F), or towards a neuroendocrine pathway, with the occurrence of many DCV. Immunogold labeling demonstrated the presence of chromogranin A in neurosecretory granules.

Calcium, calcification, and melatonin biosynthesis in the human pineal gland: A postmortem study into age‐related factors

Abstract: It is believed that pineal calcification may be age-associated and that the well-demonstrated age-related decline in melatonin biosynthesis may be an expression of an alteration in calcium homeostasis in the pinealocyte. Prior correlations of melatonin to calcium deposition and age were made on the basis of radiological or semiquantitative analysis. In this postmortem study of 33 subjects (age range 3 months to 65 years) calcium deposits measured by atomic absorption spectrometry correlated positively with age in day and night samples (day: r = 0.56, P < 0.05; night: r = 0.818, P < 0.001). Nighttime (2200 h to 0800 h) pineal melatonin content (HPLC fluorometry) was higher than daytime melatonin levels (nighttime 3.80 +/- 0.3 vs. daytime 0.85 +/- 0.4 ng/mg protein). Nighttime calcium levels in the supernatant correlated negatively with melatonin content (r = -0.59, P < 0.05).

Multiple circadian oscillators in the photosensitive pike pineal gland: A study using organ and cell culture

Abstract: Bolliet V, Begay V, Ravault J-P, Ali MA, Collin J-P, Falcon J. Multiple circadian oscillators in the photosensitive pike pineal gland: A study using organ and cell culture. J. Pineal Res. 1994: 16: 77–84. Abstract The fish pineal organ contains typical and, in some species, modified photoreceptor cells involved in the photoperiodic control of melatonin production. In the majority of species studied, the rhythm in melatonin production is driven by an intra-pineal circadian oscillator synchronized by the light: dark cycle. In the present study, it is shown that the endogenous rhythm in melatonin release of super fused pike pineals maintained under constant darkness is expressed at temperatures of 19°C, 20°C, 25°C, and 30°C (period > 24 hr), but not at temperatures of 10°C and 15°C. Under constant darkness, pineal fractions containing either typical photoreceptors, modified photoreceptors, or both behaved like total organs. Dissociated pike pineal cells, cultured statically at 20°C, expressed a high amplitude rhythm in melatonin secretion under a light: dark cycle. Under constant darkness, circadian oscillations, which appeared better sustained than in organ culture, were also observed. This study provides the first evidence that the rhythmic production of melatonin, by a fish pineal, is driven by a population of circadian oscillators or clocks. It is hypothesized that each typical and modified photoreceptor might be the locus of a circadian clock. Damping of the overall rhythm under constant darkness might reflect the resynchronization (uncoupling) between these clocks and/or damping of individual oscillators.

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

Abstract: 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.

Immunocytochemical localisation of hydroxyindole-O-methyltransferase in pineal photoreceptor cells of several fish species

Abstract: Melatonin is an internal "Zeitgeber," involved in the timing and control of a number of rhythmic functions and behaviours. Its synthesising cells remain to be identified in the fish pineal. The last step in the melatonin biosynthetic pathway is catalysed by the enzyme hydroxyindole-O-methyltransferase. An affinity-purified antibody, directed against chicken pineal hydroxyindole-O-methyltransferase, was used in the present study to identify the melatonin synthesising cells in four fish species: a primitive chondrostean (sturgeon), a saltwater teleost (dorado), and two freshwater teleosts (pike, trout). Western blot immunolabeling of pike and trout pineal proteins revealed a single band at 38 KDa, which corresponds to the known molecular weight of the enzyme in bovine, rat, and chicken pineal. Regardless of the species, a specific immunocytochemical labeling, visualised by means of the peroxidase-antiperoxidase method, was exclusively associated with the photoreceptor cells. These results provide evidence that photoreceptors of the fish pineal are responsible for the biosynthesis of 5-methoxyindoles, including melatonin. In the pike, reactions were less intense in the distal portion of the pineal vesicle than in the other regions of the organ. It is questioned whether this might be related to the existence of a germinative zone, generating new photoreceptor cells in this distal portion. Hydroxyindole-O-methyltransferase has been previously demonstrated in mammalian pinealocytes, and modified photoreceptors of the avian pineal. It is now demonstrated in pineal photoreceptors of a primitive fish and of more evolved saltwater and freshwater fish. The results strengthen the view that these cells are related through phylogeny and that their well conserved melatoninergic function appears early in the course of evolution.

Density of peptide histidine‐isoleucine‐ and vasoactive intestinal peptide‐immunoreactive nerve fibers in the sheep pineal gland is not affected by superior cervical ganglionectomy

Abstract: Peptide histidine-isoleucine (PHI) is a regulatory peptide, synthesized as part of the same propeptide that includes also vasoactive intestinal peptide (VIP). The present study describes the distribution of PHI-immunoreactive nerve fibers in the sheep pineal organ and compares their location with the distribution of VIP-immunoreactive fibers in both normal and superior cervical ganglionectomized sheep in order to elucidate the origin of the PHI/VIP immunoreactive nerve fibers. Several PHI-immunoreactive nerve fibers were present in the meninges and in the pineal capsule. Numerous positive nerve fibers entered the pineal gland and travelled within connective tissue spaces. Individual PHI-positive nerve fibers were either smooth, without specialization, or varicose. Generally VIP- and PHI-immunoreactive fibers were located close to connective septa and blood vessels. However, many PHIergic and VIPergic fibers possessing varicosities of variable sizes were also disperesed between pinealocytes. The distribution, density, and morphology of PHI- and VIP-immunoreactive fibers in the sheep pineal gland were similar. In superior cervical ganglionectomized animals, intrapineal VIP- and PHI- immunoreactive nerve fibers were present with the same density as in control animals. In agreement, the concentration of immunoreactive VIP and PHI did not change after ganglionectomy. No VIP- and PHI-immunoreactive cell bodies were observed in the superior cervical ganglia. Thus this study shows that the intrapineal VIP- and PHI-immunoreactive nerve fibers do not originate from the sympathetic superior cervical ganglion. © 1994 Wiley-Liss, Inc.

Photoreceptor-specific proteins in the mammalian pineal organ: immunocytochemical data and functional considerations.

Abstract: The mammalian pineal organ contains photoreceptor-specific proteins, whose distribution shows conspicuous variation among different species of mammals. Nevertheless, the following general conclusions can be drawn: immunoreactions for S-antigen and recoverin labeled more pinealocytes than the rod-opsin immunoreaction. The intensity of the recoverin- and S-antigen immunoreactions varied from cell to cell. alpha-Transducin immunoreaction was absent from the pineal organ of all mammals investigated with the exception of the blind mole rat. Immunoreaction for the cyclic GMP-gated cation channel was undetectable in the pineal organ of all mammals investigated. The functional significance of photoreceptor-specific proteins in the mammalian pineal organ remains unknown. It has been speculated that the S-antigen might be involved in adrenergic transduction mechanisms. To test this assumption, we have started to analyze calcium responses of single rat pinealocytes to norepinephrine stimulation using the Fura-2 technique. The cells were subsequently labeled by means of S-antigen immunocytochemistry. These combined investigations showed that variation in S-antigen immunoreactivity is not correlated with differences in the rapid calcium response to stimulation with norepinephrine. It remains to be determined whether cells displaying different intensities of the S-antigen immunoreaction show different cyclic AMP responses to noradrenergic stimulation. Investigations along this line should help to clarify further whether there is indeed a relation between the expression of S-antigen and noradrenergic transduction mechanisms in the mammalian pineal organ.

Melatonin, a hormone monitorable in vivo by voltammetry?

Abstract: Melatonin, an indoleamine hormone synthesized in the pinealocytes, is electroactive at the surface of pre-treated carbon fibre microelectrodes (mCFE)in vitro when using differential-pulse voltammetry (DPV), at the specific oxidation potential of approximately +570 mV. In vivo DPV experiments have then been performed in melatonergic regions such as the pineal gland or the suprachiasmatic nucleus (SCH) of anaesthetized adult male rats. These experiments indicated the feasibility of simultaneous measurements of the indolaminergic peak 3, which occurred at approximately +280 mV, due mainly to the oxidation of extracellular 5-hydroxyindoleacetic acid (5HIAA), and a signal at approximately +580 mV which we called peak M. Pharmacological in vivo experiments performed in anaesthetized rats prepared for DPV analysis with the mCFE implanted into the pineal gland or the SCH indicated that intravenous or intra-cerebral injections of exogenous melatonin (5 mg kg–1 or 2 µg µl–1, n= 3, respectively) were followed by a selective and significant increase of in vivo peak M. Other in vivo experiments with anaesthetized rats prepared for DPV analysis with the mCFE into the SCH showed that tryptophan [TRY, 30 mg kg–1 intravenous (i.v.), n= 3] and n-acetyl serotonin (nA-5HT, 5 mg kg–1 i.v., n= 3), both precursors of melatonin, were responsible for a transient but significant increase in the size of peak M (approximately 320% or 126% of control levels within 10 min or 20 min, respectively). The second treatment was also responsible for an increase in the size of peak 3 (216% of control values within 15 min) which may have come from an alternative route of degradation of nA-5HT into the SCH, as supported by the increased levels of both peak 3 and peak M following local injection of exogenous 5HT (1 µmol dm–3, n= 3) into the SCH. N-acetyltransferase (NAT) is one of the key enzymes controlling the synthesis of melatonin and its activity is stimulated by butyrate. Treatment of anaesthetized rats with sodium butyrate (100 mg kg–1 i.v., n= 3) produced a transient increase in the size of in vivo peak M and peak 3. In conclusion, these data suggest that DPV with pre-treated microbiosensors might be the first in vivo voltammetric method for analysis of melatonergic function(s) in melatonergic brain areas.

Glutamate immunoreactivity is enriched over pinealocytes of the gerbil pineal gland.

Abstract: Mammalian pinealocytes have been shown to contain synaptic-like microvesicles with putative secretory functions. As a first step to elucidate the possibility that pinealocyte microvesicles store messenger molecules, such as neuroactive amino acids, we have studied the distributional pattern of glutamate immunoreactivity in the pineal gland of the Mongolian gerbil (Meriones unguiculatus) at both light- and electron-microscopic levels. In semithin sections of plastic-embedded pineals, strong glutamate immunoreactivity could be detected in pinealocytes throughout the pineal gland. The density of glutamate immunolabeling in pinealocytes varied among individual cells and was mostly paralled by the density of immunostaining for synaptophysin, a major integral membrane protein of synaptic and synaptic-like vesicles. Postembedding immunogold staining of ultrathin pineal sections revealed that gold particles were enriched over pinealocytes. In particular, a high degree of immunoreactivity was associated with accumulations of microvesicles that filled dilated process terminals of pinealocytes. A positive correlation between the number of gold particles and the packing density of microvesicles was found in three out of four process terminals analyzed. However, the level of glutamate immunoreactivity in pinealocyte process endings was lower than in presumed glutamatergic nerve terminals of the cerebellum and posterior pituitary. The present results provide some evidence for a microvesicular compartmentation of glutamate in pinealocytes. Our findings thus lend support to the hypothesis that glutamate serves as an intrapineal signal molecule of physiological relevance to the neuroendocrine functions of the gland.

Calbindin‐D28k, calretinin, and recovering immunoreactivities in developing chick pineal gland

Abstract: Calbindin-D28k, calretinin, and recoverin, three intracellular calcium-binding proteins belonging to the troponin C/calmodulin superfamily, were immunohistochemically localized in chick pineal during development [from embryonic day 16 (E16) to postnatal day 14 (P14)]. At E18, only calretinin immunoreactivity could be detected in nuclei from follicular pinealocytes. With development, calretinin immunoreactivity expanded from nucleus to cytoplasm, and calretinin immuno-positive cell number increased. At P14 almost al pinealocytes were calretinin positive. Calbindin-D28k immunoreactivity was not detected before E20. During development, many follicular and parafollicular pinealocytes became strongly calbindin-D28k positive, reaching a peak both in intensity and in number at P7; thereafter their number decreased. In addition to pinealocytes, neuron-like cells appeared calbindin-D28k positive at E20 and calretinin positive at P7. Recoverin, a myristoylated protein isolated from vertebrate photoreceptor and which might participate in the inactivation of the phototransduction cascade, was transiently expressed in follicular and parafollicular pinealocytes from P1 to P14 with a maximal expression at P7. This transitory expression may coincide with a transitory light sensitivity period in chick pinealocytes, before complete maturity of the pineal gland.

Nor epinephrine induces Ca2+ release from intracellular stores in rat pinealocytes

Abstract: In rat pinealocytes, an increase in intracellular Ca2+ concentration ([Ca2+]i) due to Ca2+ influx in response to norepinephrine (NE) is a well recognized event involved in regulating several metabolic functions. Since NE also stimulates the metabolism of phosphatidyl inositols in rat pineal gland, it is conceivable that Ca2+ release from intracellular stores also contributes to the NE-induced increase in [Ca2+]i. In this communication, we report that in rat pinealocytes loaded with fura-2, a Ca2+ indicator, NE induced a transient increase in [Ca2+]i that preceded the known Ca2+ influx. This novel [Ca2+]i response to NE was detected in pinealocytes bathed with Ca2+-free saline and prevented by TMB-8, a blocker of Ca2+ release from intracellular stores, supporting the notion that the transient NE-induced Ca2+ response was due to Ca2+ release from intracellular stores. In addition, after an extended exposure to NE a new addition of this neurotransmitter did not elicit the phasic Ca2+ response, and application of increasing amounts of NE induced a Ca2+ response that was progressively smaller, suggesting desensitization. Thus, NE is proposed to increase [Ca2+]i in rat pinealocytes by two mechanisms: (1) phasic release from intracellular stores and (2) tonic influx through a mechanism activated by larger applications of NE than required to evoke the phasic release.

The presence of nerve fibers immunoreactive for vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), and preproVIP(111–122) in the mouse pineal gland

Abstract: Mikkelsen JD, Moller M, Larsen PJ, Fahrenkrug J. The presence of nerve fibers immunoreactive for vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), and preproVIP(111-l22) in the mouse pineal gland. J. Pineal Res. 1994: 16: 50–56. Abstract A low to moderate number of vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI)-immunoreactive nerve fibers with prominent boutons-en-passage were demonstrated in the pineal gland of the mouse. The two peptides, which are parts of the same precursor molecule, were distributed identically in the gland. Positive fibers were present in the connective tissue septae in the gland, in the pineal capsule, and in the pineal parenchyma. No VIP-PHI-immunoreactive elements were found in the deep pineal gland, in the pineal stalk, or in habenular and posterior commissures. This morphological distribution of immunoreactive nerve fibers, which is similar to the distribution in other mammals, indicates that the VIP/PHI fibers of the mouse pineal gland originate exclusively from perikarya in a peripheral ganglion, presumably one of the cholinergic ganglia of the head. No evidence for a VIPergic central innervation was found. VIP and PHI are connected via a bridging peptide equivalent to amino acids 111-122 of the precursor (preproVIP(111-122)). In order to demonstrate the possible existence of this peptide in intra-pineal nerve fibers, antisera directed against a synthetic sequence identical to pre-proVIP(111–122) and immunohistochemistry were applied. Abstract PreproVIP(111-122)-immunoreactive nerve fibers were observed in the mouse pineal gland, with the same distribution pattern and morphology as those immunoreactive for VIP and PHI. To quantify the peptide-immunoreactivities, 50 mice pineals were pooled, extracted, and the concentrations were measured radioimmunologically. The concentrations of the VIP and preproVIP(111–122) immunoreactivities were 1.7 and 2.0 pmol/g, respectively, whereas the concentration of PHI was 0.9 pmol/g. This indicates that not only VIP and PHI, but also other fragments of preproVIP are present in the mammalian pineal gland. Whereas the stimulatory role of VIP is well documented, the effect of other fragments processed from preproVIP on pinealocytes remains to be established.

Analysis of the heterogeneity within bovine pineal gland by immunohistochemistry and in situ hybridization.

Abstract: In the present study, we demonstrate a cortical and medullary arrangement of parenchymal cells in the bovine pineal gland by using antibodies for neuronspecific enolase, synaptophysin, and hydroxyindole O-methyltransferase (HIOMT) as markers of pinealocytes, and glial fibrillary acidic protein (GFAP) as a marker of interstitial (glial) cells. Furthermore, by means of probes specific for HIOMT mRNA, we have examined possible differences in melatonin synthesis between the cortex and the medulla. Immunoreactive pinealocytes for each antigen investigated are more densely distributed in the cortex than in the medulla. In the cortex, GFAP-positive interstitial cells have large intenselystained somata endowed with several long, thin cytoplasmic processes, whereas in the medulla, they display smaller, less intensely labeled perikarya from which numerous fine short processes emerge. Golgi staining has confirmed these morphological differences between the interstitial cells in the cortex and those in the medulla. An analysis using confocal laser microscopy together with in situ hybridization for HIOMT mRNA has shown that the expression of mRNA transcripts in the cortex is more intense than that in the medulla. The expression of the HIOMT gene in a cluster of cells in the medial habenular nucleus is lower than that in pinealocytes of the pineal organ proper.

Distribution of calcified concretions and calcium ions in the pig pineal gland.

Abstract: Serial sections of pig pineal glands were stained with von Kossa's and Alizarin red S methods to determine the occurrence and localization of calcified concretions. In the pineal glands of pigs aged eight months, concretions were not found. A small number of concretions was observed in all investigated pineal glands of three years old pigs. The concretions were distributed in the connective tissue of the pineal capsule and septa. The potassium pyroantimonate method was used for ultracytochemical localization of calcium ions. In pinealocytes, precipitates were observed in nuclei, mitochondria, Golgi apparatus, endoplasmic reticulum and cytoplasmic matrix. Single precipitates were found on the outer membranes of dense bodies, multivesicular bodies and lysosomes. There were no differences in the amount or the localization of precipitates between dark and light pinealocytes and between pinealocytes of animals aged both eight months and three years. The results suggest that: (1) the calcified concretions in the pig pineal gland are formed by the leptomeningeal tissue without participation of the pinealocytes, (2) cytoplasmic dense bodies, specific components of the pig pineal gland, are only slightly involved in calcium turnover in the pinealocytes.

Innervation of the cat pineal gland by neuropeptide Y-immunoreactive nerve fibers: an experimental immunohistochemical study.

Abstract: An immunohistochemical study of the cat pineal gland was performed using a rabbit polyclonal antibody directed against neuropeptide Y (NPY) and an antibody directed against the C-terminal flanking peptide of neuropeptide Y (CPON). Numerous NPY- and CPON-immunoreactive (IR) nerve fibers were demonstrated throughout the gland and in the pineal capsule. The number of IR nerve fibers in the capsule was high and from this location fibers were observed to penetrate into the gland proper via the pineal connective tissue septa, often following the blood vessels. From the connective tissue septa IR fibers intruded into the parenchyma between the pinealocytes. Many IR nerve fibers were observed in the pineal stalk and in the habenular as well as the posterior commissural areas. The number of NPY/CPON-IR nerve fibers in pineal glands from animals bilaterally ganglionectomized two weeks before sacrifice was low. The source of most of the extrasympathetic NPY/CPONergic nerve fibers is probably the brain from where they enter the pineal via the pineal stalk. However, an origin of some of the fibers from parasympathetic ganglia cannot be excluded due to the presence of a few IR fibers in the pineal capsule of ganglionectomized animals. It is concluded that the cat pineal is richly innervated with NPYergic nerve fibers mostly of sympathetic origin. The posttranslational processing of the NPY promolecule results in the presence of both NPY and CPON in intrapineal nerve fibers.

Melatonin disturbances in anorexia nervosa and bulimia nervosa.

Abstract: The pineal gland releases melatonin into the blood stream in response to sympathetic noradrenergic stimulation of pinealocytes. This process is inhibited by light via the retino-hypothalamic-pineal pathway. Hence melatonin is predominantly released in darkness. Because serotonin is a precursor of melatonin, the intake of dietary tryptophan may also influence melatonin levels. Although the exact physiological role of melatonin in humans is unclear, it appears to be implicated in reproductive physiology, especially in terms of the onset of menarche. Low levels of melatonin also occur in depression. In this review, studies of melatonin in patients with anorexia nervosa and bulimia nervosa are considered in relation to potential abnormalities of noradrenergic function and circadian rhythm. The influence of weight loss, binging and purging, and depression on melatonin is discussed. Other studies involving the assessment of melatonin in relation to menstrual function are required. © 1994 by John Wiley & Sons, Inc.

Calmodulin immunoreactivity in the chicken pineal gland: comparison with calbindin-D28k, calretinin, and S100.

Abstract: Calmodulin distribution in the chicken pineal organ was investigated by immunohistochemistry. Calmodulin immunoreactivity was detected in ependymocytes in the follicular zone and in interstitial cells in the parafollicular zone. No calmodulin immunoreactivity was detected in pinealocytes. Lack of calmodulin immunoreactivity in pinealocytes raises questions about its proposed function in melatonin synthesis as suggested by pharmacological studies using calmodulin antagonists. The calmodulin distribution was comparable to that of S100, a glial cell marker. Two other markers, calbindin-D28k and calretinin, which in neuroanatomical studies give excellent cytoarchitectonic staining, in the chick pineal permitted the detection of two subclasses of pinealocytes. One was darkly stained by calbindin-D28k and rare. The other was very abundant and calretinin positive. In the parafollicular zone, calbindin-D28k and/or calretinin antibodies allowed us to visualize cells presenting a neuron-like morphology. Calretinin immunoreactivity was detected in nearly all pinealocytes in which hydroxy-indol-O-methyl transferase was also located. Comparison between the lack of calmodulin and the presence of calretinin, belonging to the same calcium-binding protein family, in chick pinealocytes raises the hypothesis about a possible role of calretinin in melatonin synthesis.

Clonidine in vivo mimics the acute suppressive but not the phase-shifting effects of light on circadian rhythm of serotonin N-acetyltransferase activity in chick pineal gland.

Abstract: Zawilska JB. Clonidine in vivo mimics the acute suppressive but not the phase-shifting effects of light on circadian rhythm of serotonin N-acetyltransferase activity in chick pineal gland. J. Pineal Res. 1994; 17: 63–68. ©Munksgaard, 1994 Abstract Comparative in vivo studies on effects of pulses of light and clonidine, a selective agonist of α2-adrenergic receptors, on the circadian rhythm of serotonin N-acetyltransferase (NAT) activity in chick pineal gland were performed. Six-hour pulses of white light caused an acute suppression of the nocturnal NAT activity and phase-dependent phase shifts of the circadian rhythm of the enzyme activity relative to controls. Systemic administration of clonidine acutely suppressed NAT activity of chick pineal gland, but did not affect the phase of subsequent cycles in constant darkness. These results give further support to the concept based on in vitro studies that α2-adrenergic receptors are involved in regulation of melatonin biosynthesis in chick pineal gland by a mechanism distal to the pacemaker that generates the circadian melatonin rhythm.

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

Abstract: Marin F, Boya J, Calvo JL, Lopez‐Munoz F, Garcia‐Maurino JE. Immunocytochemical localization of basic fibroblast growth factor in the rat pineal gland. J. Pineal Res. 1994: 16: 44–49. 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 neutrophic factors. Copyright © 1994, Wiley Blackwell. All rights reserved