Biomedical subjects

S Reuss

Publications and source records attributed to S Reuss.

At least 37 records · Page 2Linked to original sources

PubMed1998

Circadian rhythm and effects of light on cAMP content of the dwarf hamster suprachiasmatic nucleus.

The present study was conducted in the dwarf hamster (Phodopus sungorus) to investigate whether a circadian rhythm is present in the content of the second messenger cyclic adenosine 3',5'-monophosphate (cAMP) in the suprachiasmatic nucleus (SCN), the endogenous clock in mammals. In animals held under light/dark conditions (LD), we observed high levels at the end of the light phase and low levels during the night in frozen SCN punches. In animals held in continuous dark, a similar rhythm was seen although a second peak was present in the subjective day. In senile hamsters under LD, the decrease of cAMP levels at the light transition was not seen. These data, obtained for the first time from hamsters, support the view that cAMP is involved in time-keeping mechanisms within the SCN.

Animals↗

PubMed1998

Chronical haloperidol and clozapine treatment in rats: differential RNA display analysis, behavioral studies and serum level determination.

1. Adult, female rats were treated orally for 23 days with 1.6 mg/kg haloperidol or 36 mg/kg clozapine per day, to study chronic effects of the two neuroleptics. 2. At five time points during the neuroleptic treatment, animal behavior was recorded in an open field and locomotive activity was analysed. At the end of the experiment, rats were decapitated, blood samples were collected and serum concentrations of haloperidol and clozapine were determined by a radioreceptor or HPLC assay, respectively. RNA was isolated from each brain, without cerebellum, and subjected to differential RNA display. 3. Mean serum concentrations were 8 ng/ml for haloperidol and 21 ng/ml for clozapine. Analysis of open field behavior showed that haloperidol and clozapine decreased the total distance moved and the velocity as measures of the overall activity, whereas the number of rearings and the number of entries into the center, reflecting risk assessment behavior, were differentially affected. Three neuroleptic-regulated gene fragment bands were identified in differential RNA display experiments. Two gene fragments of 281 bp and 266 bp were sequenced. 4. We conclude that our study design that used behavioral, pharmacokinetic and molecular analysis increase the likelihood of finding relevant molecular events underlying the pharmacotherapeutic effects of neuroleptics in animal models.

Animals↗

PubMed1997

Molecular cloning of rat G-protein-coupled receptor kinase 6 (GRK6) from brain tissue, and its mRNA expression in different brain regions and peripheral tissues.

The rat G-protein-coupled receptor kinase 6 (GRK6) cDNA was cloned from rat brain tissue by a combination of reverse-transcription polymerase chain reactions (RT-PCR), based on homology to the cloned human GRK6, and rapid amplification of cDNA ends (RACE-PCR). We obtained a clone of 2817 bp with an open reading frame of 1731 bp encoding for a protein of 576 amino acids that is 96.7% identical and 97.9% similar to its human counterpart. mRNA was detectable in all brain areas examined. In addition, GRK6 was expressed in skeletal muscle, small intestine, aorta, liver, heart, lung, thymus, stomach, uterus and kidney.

Amino Acid Sequence↗

PubMed1997

Stimulation of immediate early gene expression by desipramine in rat brain.

The stimulation of immediate early gene expression in brain and neuronal cell culture systems has been reported after various experimental paradigms such as chemiconvulsant-provoked seizures or specific drug applications. In particular, the induction of immediate early genes by adrenergic model substances has been demonstrated by several investigators. This report demonstrates that a single dose of desipramine (10 or 25 mg/kg), a classical tricyclic antidepressant drug acting on the adrenergic system, induced c-fos and zif268 expression in rat hippocampus without affecting c-jun. The observed immediate early gene response might reflect part of a signal transduction cascade involved in long-term neuroadaptive and behavioral changes after antidepressant drug treatment.

Animals↗

PubMed1997

Anterograde tracing of retinohypothalamic afferents with Fluoro-Gold.

The anterograde neuronal tracing properties of Fluoro-Gold (FG) were characterized in this study by its ability to label the retinohypothalamic tract (RHT) upon pressure injection of the substance into the vitrous body of the eye in the Djungarian hamster, Phodopus sungorus. Tracing was compared to the anterograde neuronal transport of cholera toxin B subunit (CTB), Fast blue (FB), Phaseolous vulgaris leucoagglutinin (PHA-L) and biocytin. After survival times that ranged from 24 h to 4 weeks, a major projection was found to the bilateral hypothalamic suprachiasmatic nuclei (SCN). Labeling was also found in the anterior medial preoptic nucleus and, in relatively sparse amounts, in the lateral geniculate nucleus, superior colliculus and lateral habenular nucleus. Similar results were obtained upon injection of CTB or FB, respectively, into the eye, whereas the application of PHA-L or biocytin did not label retinal afferents. The combined injection of FG and CTB or FB into the same eye labeled retino-afferent fibers only when FG was applied three days before the injection of the other tracers. Retrogradely labelled neurons were sen occasionally in the hypothalamus which may provide a sparse retinopetal projection. Additional experiments combining FG tracing and the immunofluorescent detection of the neuropeptides substance P (SP) or vasoactive intestinal polypeptide (VIP) in the SCN showed that FG-containing punctae were accumulated in the vicinity of immunoreactive cell bodies. Our data demonstrate that FG may be used as an anterograde axonal tracer of the retinohypothalamic pathway.

Amidines↗

PubMed1996

Expression of alpha subunit genes of nicotinic acetylcholine receptors in human lymphocytes.

Using immunohistochemistry and in situ hybridisation, we have studied whether alpha-subunits of nicotinic acetylcholine receptors (nAChRs) are expressed in human lymphocytes. Cells were isolated by differential low speed gradient centrifugation from heparinised venous blood of 10 healthy volunteers. Receptor sites were visualised using the monoclonal antibody WF6 which specifically recognises alpha-isoforms from several species including man. For visualisation of transcripts, digoxigenin-labelled cRNA probes for alpha 4- and alpha 3-subunits were used. Immunostaining revealed specific binding of WF6 to isolated human lymphoid cells. The antibody was bound to most cells and concentrated preferentially in the perinuclear/surface region. The immunoreactivity resembled that observed after application of an antibody recognising CD4 surface proteins which was conducted for comparison. In situ-hybridisation revealed that the alpha 4-subunit genes of nAChRs was expressed in lymphocytes of all probands. The alpha 3-subunit was found, with lower intensity than alpha 4-transcripts, in eight of the 10 individuals. Control incubations with corresponding sense cRNAs were negative. It is concluded that human lymphocytes are able to express alpha-subunit genes of nAChRs.

Adult↗

PubMed1996

Is there a direct retina-raphe-suprachiasmatic nucleus pathway in the rat?

Possible pathways from the retina to the suprachiasmatic nucleus (SCN) relaying in the dorsal raphe nucleus (DRN) were investigated in rats using combined anterograde and retrograde tracing with immunohistochemistry. After injection of wheat germ agglutinin-conjugated horseradish peroxidase-colloidal gold complex into the SCN, many neurons were retrogradely labeled in the middle levels of the DRN. Approximately one half of these neurons contained serotonin. After injection of cholera toxin B subunit into the eyes, a few anterogradely labeled afferent fibers were detected in the rostral DRN, however, not in contact with retrogradely labeled neurons. Our findings provide direct evidence that serotonergic projections to the rat SCN stem from the DRN nuclei. They also suggest that retina-raphe-SCN projections, a presumed third visual input to the mammalian circadian pacemaker, may include further neuronal connections or brain sites.

Animals↗

PubMed1996

Components and connections of the circadian timing system in mammals.

The circadian timing system is a neural network consisting of the hypothalamic suprachiasmatic nucleus, aided by the retina, other hypothalamic nuclei, autonomic regions of the spinal cord, sympathetic ganglia and the pineal gland. Extensive studies conducted over the last two decades have unravelled the principal items of its functional neuroanatomy. The system is responsible for the generation of the circadian rhythm, its synchronization by environmental factors such as light, and its mediation with respect to morphological, physiological and biochemical parameters of mammals that exhibit distinct alterations throughout the 24-h cycle. This review characterizes the brain sites involved and the pathways responsible for the generation and maintenance of circadian rhythmicity.

Animals↗

PubMed1996

Induction of c-fos gene expression by the selective sigma receptor ligand EMD 57445 in rat brain.

Based on animal studies it has been reasoned that ligands to sigma binding sites might be effective in the treatment of schizophrenic disorders and may also be used to investigate this largely elusive disorder on a molecular level. Expression patterns of c-fos in rat brain were studied following treatment with single doses of the sigma ligand EMD 57445 (0.3, 1, 3, 30 mg/kg s.c.). Specific c-fos gene expression was detected at all concentrations tested in various cortical areas. The signals observed were dose-dependent with the highest intensities in the piriform cortex. Strong signals were also detected in hippocampal areas CA 1,2,3 and the gyrus dentatus, as well as in the medial habenula nuclei. In the caudate putamen, nucleus accumbens and lateral septal nucleus signals were detectable after administration of doses > or = 1 mg/kg. Furthermore, c-fos hybridization was visible in the amygdala, in the mammillary bodies, the islands of Calleja and in the olfactory tubercle. In the hypothalamus, c-fos expression was seen in the median eminence area after 30 mg/kg EMD 57445. No hybridization signals were obtained in brainstem or cerebellum. Since c-fos expression induced by EMD 57445 resembled the pattern obtained with atypical neuroleptics and studies on animal behavior point to antipsychotic activity, it is concluded that the drug might be suitable in the treatment of schizophrenia.

Animals↗

PubMed1995

Nitric oxide synthase in the hypothalamic suprachiasmatic nucleus of rat: evidence from histochemistry, immunohistochemistry and western blot; and colocalization with VIP.

Nitric oxide (NO) is a neuroactive substance of high potency. Physiological results revealed the involvement of NO in circadian regulation of rats. Since neuronal structures containing NO-synthase (NOS) were previously not found in the circadian oscillator, the hypothalamic suprachiasmatic nucleus (SCN), in this species but are present in the hamster, we investigated the distribution of NO-producing structures in the rat SCN by Western blot analysis, immunohistochemistry of NOS, and by histochemistry (NADPH-diaphorase (NADPH-d) activity of NOS). Western blot analysis of SCN homogenates from rat (and, for comparison, hamster) showed a NOS-like immunoreactive (-LI) protein band of apparent molecular mass of 150 kDa, consistent with the neuronal NOS molecule. In the rat SCN, perikarya exhibiting NADPH-d staining of NOS-LI with a complete overlapping of both were found. Double-immunofluorescence experiments revealed that NOS cells are a subgroup of the neuronal SCN population that is characterized by immunoreactivity to vasoactive intestinal polypeptide. These data provide evidence for the existence of neuronal nitric oxide synthase in the rat SCN and may explain the involvement of NO in the mediation of photic information.

Animals↗

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↗

PubMed1995

Down-regulation of the nocturnally elevated guanylyl cyclase activity in the rat pineal gland.

Previous studies have shown that in the rat pineal, the cytosolic and the particulate forms of guanylyl cyclase (GC) activity undergo a biphasic 24-h rhythm with two prominent peaks, one in the middle of the light phase and the other in the middle of the dark phase. In this study we investigated whether the well established photo-neural adrenergic regulatory processes identified for pineal melatonin synthesis also apply to the nocturnal elevation of GC activity. A 10-min light pulse given in the middle of the dark phase decreases the cytosolic and the particulate forms of GC. Administration of the beta-receptor blocker propranolol did not depress the nocturnally elevated GC activity. Sympathetic denervation of the pineal gland by means of superior cervical ganglionectomy did not noticeably affect nocturnal GC activity studied 6 days and 2 months after surgery. In vitro, administration of the nitric oxide synthase blocker NG-mono-methyl-L-arginine (NMMA) for 10 min did not change the cytosolic form of GC activity. The results obtained reveal that in the rat pineal, the down-regulation of the nocturnally elevated GC activity does not appear to be adrenergically mediated.

Animals↗

PubMed1995

Pineal 'synaptic' ribbon numbers and melatonin synthesis of rat are resistant to guanethidine sympathectomy.

Chemical sympathectomy is widely used to study the impact of the noradrenergic system on neuronal and neuroendocrine circuits. We tested the effects of intraperitoneal injections of guanethidine, an adrenergic neuron blocking agent, on selected functional parameters of the rat pineal gland which are known to be under sympathetic influence. The reliability of the method was demonstrated by the clear enophthalmus developed by experimental animals. However, neither the numbers of 'synaptic' ribbons nor melatonin synthesis differed between treated and control rats, both parameters exhibiting the nocturnal increase seen in intact animals. These results are in striking contrast to those obtained upon chemical sympathectomy with 6-hydroxydopamine or surgical superior cervical ganglionectomy. We conclude that guanethidine is not capable of sufficiently removing noradrenergic influence from the rat pineal gland, and that this substance is thus inferior to other experimental methods of sympathectomy.

Animals↗

PubMed1995

Demonstration of retinal afferents in the RCS rat, with reference to the retinohypothalamic projection and suprachiasmatic nucleus.

In the Royal College of Surgeons (RCS) rat, characterized by inherited retinal dystrophy, retinal projections to the brain were studied using anterograde neuronal transport of cholera toxin B subunit upon injection into one eye. The respective immunoreactivity was found predominantly contralateral to the injection site in the lateral geniculate nucleus, superior colliculus, nucleus of the optic tract, medial terminal nucleus of the accessory optic tract, and bilateral hypothalamic suprachiasmatic nuclei. Although terminal density was somewhat reduced in dystrophic rats, the projection patterns in these animals appeared similar to those seen in their congenic controls and were comparable to the visual pathways described for the rat previously. In dystrophic rats, the number of cell bodies exhibiting immunoreactivity to vasoactive intestinal polypeptide, viz. a population of suprachiasmatic neurons receiving major retinohypothalamic input, was reduced by one-third, and some differences were observed in the termination pattern of the geniculohypothalamic tract, as revealed by immunoreactivity to neuropeptide Y in the suprachiasmatic nucleus.

Afferent Pathways↗

PubMed1995

Neuropeptide Y: distribution of immunoreactivity and quantitative analysis in diencephalic structures and cerebral cortex of dwarf hamsters under different photoperiods.

The distribution of neuropeptide Y-like immunoreactivity (NPY-LI) was investigated by immunohistochemistry and radioimmunoassay (RIA) in the brain of the Djungarian hamster (Phodopus sungorus) held under either long or short photoperiods. In the diencephalic and telencephalic structures studied, distinct patterns of NPY-LI were basically consistent in male and female animals of both groups. NPY levels detected by RIA from tissue samples taken at six time points throughout the 24-hour cycle were in the range of 15-60 pmol/mg protein in the diencephalon or below 5 pmol/mg protein in cerebral cortex. In the diencephalon, immunoreactive structures were seen in the preoptic, peri- and paraventricular, supraoptic, anterior, lateral, dorso- and ventromedial hypothalamic nuclei and in the median eminence. The suprachiasmatic nuclei exhibited a dense innervation by NPY-LI terminals mainly in its ventrolateral subdivision. NPY levels in the suprachiasmatic nucleus were nocturnally augmented under long-day, but not under short-day conditions. The quantification of NPY in the paraventricular nucleus revealed a decrease at night in long-day animals and a small nocturnal augmentation in short-day hamsters. In the pineal gland and habenular nuclei, varicose fibers were observed which appeared mainly perivascular in location (pineal) or formed a dense plexus (habenular nuclei). Pineal NPY contents fell during the night in long-day animals and were relatively constant in short-day hamsters. NPY-LI structures were also observed in the metathalamic intergeniculate leaflet and in a variety of telencephalic structures including the cerebral cortex, caudate nucleus putamen, lateral septal nucleus, bed nucleus of the stria terminalis and amygdala.

Animals↗

PubMed1994

Nitric oxide-synthesizing neurons in the hamster suprachiasmatic nucleus: a combined NOS- and NADPH- staining and retinohypothalamic tract tracing study.

Neuronal nitric oxide (NO), thought to be a neuroactive substance of high potency, is produced by the enzyme nitric oxide synthase (NOS) which has been demonstrated to additionally exhibit a so-called NADPH-diaphorase (NADPH-d) activity. Since physiological results pointed to the involvement of NO in circadian regulation, and morphological descriptions are not available, we sought to study the distribution of NO-producing cells in the hypothalamic suprachiasmatic nucleus (SCN) in Djungarian hamsters (Phodopus sungorus) by means of histochemistry and immunohistochemistry (IHC). In the SCN, NADPH-d stained perikarya of varying intensity and number were found predominantly in the ventrolateral subdivision. Diaphorase staining combined with the IHC demonstration of NOS revealed a complete overlapping of both. The combination of NADPH-d staining with the demonstration of the retinohypothalamic tract using the anterograde neuronal transport of cholera toxin B (CTB) following intraocular injection showed CTB terminals accumulating at NADPH-d cell bodies mainly in the ventrolateral region of the SCN. These data provide morphological evidence for the involvement of nitric oxide in the mediation of photic stimulation of the circadian oscillator located in the SCN.

Animals↗

PubMed1994

Day- and nighttime content of monoamines and their metabolites in the pineal gland of rat and hamster.

Day- and nighttime content of catecholamines, serotonin and their metabolites were measured in the pineal gland of Sprague-Dawley rats and Djungarian hamsters. In addition, monoamine turnover rates were determined in the hamster pineal gland following administration of alpha-methyl-p-tyrosine. Animals were decapitated in the middle of the light or dark period, respectively, and pineal tissue was analysed by high performance liquid chromatography with electrochemical detection. Pineals of both species exhibited day/night-differences in serotonin, 5-hydroxyindole-3-acetic acid and dopamine content. The hamster pineal gland further showed day/night differences in its content of epinephrine and 3-methoxy-4-hydroxyphenylethyleneglycol. The dopamine turnover rate was augmented at night, while norepinephrine turnover was constant. Immunohistochemical incubations of pineal paraffine sections showed fibers and terminals stained by antisera to tyrosine-hydroxylase (TH) and dopamine-beta-hydroxylase, and a few perikarya-like structures exhibiting TH immunoreactivity. The results support the view that dopamine, rather than only functioning as a norepinephrine precursor, is actively involved in the control of melatonin synthesis.

Animals↗

PubMed1994

Anterograde neuronal tracing of retinohypothalamic projections in the hamster--possible innervation of substance P-containing neurons in the suprachiasmatic nucleus.

The retinohypothalamic tract (RHT) in the Djungarian hamster Phodopus sungorus was studied using anterograde neuronal transport of cholera toxin subunit B (CTB) following unilateral intraocular injection. A major projection terminates bilaterally in the hypothalamic suprachiasmatic nuclei (SCN). In the anterior ventral SCN, a light ipsilateral predominance was evident. In the medial SCN, labelling was concentrated laterally where it was seen over the dorso-ventral extension of the nuclei, pronounced contralaterally to the site of CTB injection, which was even more characteristic in the posterior aspects of the nuclei. Labelled fibers and terminals were observed in the supraoptic nuclei, but not in lateral and paraventricular hypothalamic regions. Additional experiments utilizing double immunofluorescence of CTB and of substance P (SP) in the SCN showed that SP-containing perikarya were particularly observed in a central portion of the nucleus, where CTB-stained terminals were accumulated in the vicinity of immunoreactive cell bodies, fibers and terminals. Our data provide preliminary morphological evidence for the regulation of SCN function by retinal afferents and may explain the circadian and photoperiodic fluctuations in the amount of SP in the SCN.

Animals↗