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O Bosler

Publications and source records attributed to O Bosler.

At least 55 records · Page 3Linked to original sources
PubMed1988

Serotonin innervation of neuropeptide Y-containing neurons in the rat arcuate nucleus.

Structural non-synaptic appositions between serotonin (5-HT) nerve endings and neuropeptide Y (NPY)-containing neurons were demonstrated in the rat arcuate nucleus by means of a combined radioautographic and immunocytochemical detection of [3H]5-HT uptake sites and NPY-immunoreactivity. Such cellular relationships are proposed to constitute a morphological substrate for putative 5-HT/NPY interactions in neuroendocrine hypothalamus.

Animals↗
PubMed1988

Central serotonergic projections to the nucleus tractus solitarii: evidence from a double labeling study in the rat.

Projections from several brainstem serotonergic nuclei to the nucleus tractus solitarii were investigated in the rat. Experiments were performed using a double labeling method combining retrograde radioautographic tracing and serotonin immunohistochemistry. After injection of the radioactive tracer ([3H] wheat germ agglutinin) into the lateral nucleus tractus solitarii, nerve cell bodies exhibiting both radioautographic labeling and immunostaining were detected in all the serotonergic nuclei investigated, namely the nucleus raphe magnus, the ventromedial paragigantocellular nucleus, the nuclei raphe pontis, medianus and dorsalis, the medial lemniscus and the reticulotegmental nucleus of the pons. Most of the double labeled perikarya observed were in the nucleus raphe magnus, the adjacent part of the paragigantocellular nucleus and the nucleus raphe dorsalis. Nerve cell bodies retrogradely labeled but devoid of immunostaining were also observed, together with the double labeled perikarya, within serotonergic nuclei. These results provide direct evidence that brainstem serotonergic neurons contribute to the innervation of the nucleus tractus solitarii. They indicate that the nucleus raphe magnus and the nucleus raphe dorsalis constitute two major sources of central serotonergic projections to the nucleus tractus solitarii.

Animals↗
PubMed1987

Electron-microscopic characterization of adrenergic axon terminals in the diencephalon of the rat.

The fine structure of adrenergic axon terminals was examined in the paraventricular nucleus of the thalamus (PNT) and in the hypothalamic arcuate nucleus-median eminence (ARC-ME) complex by use of phenylethanolamine-N-methyl transferase (PNMT) immunocytochemistry. In the PNT, immunoreactive terminals formed a dense and well-circumscribed plexus. In the ARC, labeled varicosities were less numerous and more evenly distributed. In the ME, they were scarce and confined to the inner zone. In all these areas, the diameter of immunoreactive varicosities ranged between 0.2 and 1.3 micron; in the ME and in the transitional zone between the ARC and the ME, a population of larger boutons (greater than 2 microns) was also visible. All immunoreactive varicosities exhibited densely packed small, clear vesicles associated with a few large granular vesicles. In the PNT and the ARC, but not in the ME, they formed synaptic contacts with dendritic elements and were occasionally apposed to neuronal cell bodies. These axo-somatic appositions showed no junctional specializations. In the ME and transitional zone, immunoreactive terminals were frequently juxtaposed to, and occasionally established differentiated synaptic contacts with, tanycytes. These data support a transmitter role for adrenaline in the diencephalon and suggest that adrenaline plays a role in hypothalamo-hypophysiotropic regulation through interactions with neural and glial elements.

Animals↗
PubMed1987

Morphological correlates of serotonin-neuropeptide Y interactions in the rat suprachiasmatic nucleus: combined radioautographic and immunocytochemical data.

The morphological substrate of putative serotonin (5-HT)/neuropeptide Y (NPY) interactions in the suprachiasmatic nucleus (SCN) was investigated by combined radioautography and immunocytochemistry after intraventricular administration of (3H)5-HT in the rat. In the ventral portion of the SCN, the distribution of (3H)5-HT uptake sites overlapped closely the NPY-immunoreactive terminals. Previous investigations have shown that the dense 5-HT and NPY innervations of the SCN originate in different structures, i.e., the midbrain raphe nuclei and the ventral lateral geniculate nucleus, respectively. Accordingly, in the present study, destruction of 5-HT afferents by 5,7-dihydroxytryptamine was not found to induce any modification in NPY staining and, in ultrastructural immuno-radioautographic preparations, two distinct pools of axonal varicosities could be identified. Both 5-HT and NPY terminals established morphologically defined synaptic junctions, sometimes on the same neuronal target. Some cases of direct axo-axonic appositions between the two types of terminals were also encountered. These data constitute additional criteria for characterizing the cytological basis of the multiple transmitter interactions presumably involved in the function of the SCN as a central regulator of circadian biological rhythms.

Animals↗
PubMed1987

GABA nerve endings in the rat red nucleus combined detection with serotonin terminals using dual immunocytochemistry.

Immunocytochemical methods were used to examine the ultrastructural features and cellular interrelationships of GABA and serotonin afferent fibers to the rat red nucleus. GABAergic nerve endings were identified in two ways, either using a pre-embedding immunoperoxidase procedure with an antibody against glutamate decarboxylase, the GABA-synthesizing enzyme, or after post-embedding immunogold labelling with an anti-GABA antibody. With the latter approach, it was possible to simultaneously visualize the GABAergic and serotoninergic innervation of the red nucleus (magnocellular part) in electron microscope preparations. This procedure involved GABA labelling of ultrathin sections obtained from specimens previously immunostained for serotonin using the pre-embedding peroxidase-antiperoxidase technique. The doubly stained sections showed gold and peroxidase markers to be present in two distinct populations of axonal varicosities. Unlike the GABAergic nerve endings, which were found to be profusely distributed throughout the nucleus, the serotonin nerve endings were relatively scarce. They contacted dendrites of large-sized neurons usually endowed with several GABA-gold labelled terminals. Not uncommonly, direct appositions between serotonin and GABA-positive terminals were also encountered. These data provide morphological evidence that red nucleus outputs may be dually regulated by GABAergic and serotoninergic afferents, while suggesting that presynaptic GABA/serotonin interactions might also play a significant part in red nucleus functions.

Animals↗
PubMed1987

Serotonin and serotoninergic neurons. A radioautographic and immunocytochemical study of the nucleus raphe dorsalis and nucleus dorsomedialis hypothalami.

In an attempt to define cytophysiological criteria with which to establish whether or not a given neuron is serotoninergic, radioautography was combined with serotonin (5-HT) immunocytochemistry on the same sections from the nucleus raphe dorsalis (NRD) and/or nucleus dorsomedialis hypothalami (NDM) in rats subjected to intraventricular administrations of (3H)-5-HT or (3H)-dopamine (DA). All the (3H)-5-HT-accumulating neurons (cell bodies, dendrites and terminals) were found to be distinct from the (3H)-DA labeled ones and invariably immunostained for 5-HT in both regions studied. However, some immunoreactive neuronal elements within the area of tracer diffusion did not exhibit significant radioautographic labeling. In the NDM where 5-HT immunoreactive nerve cells could be detected only after intraventricular administration of 5-HT, these were found to be definitely distinct from the tyrosine hydroxylase immunoreactive and (3H)-DA labeled neurons of the dopaminergic periventricular-arcuate complex. After immunostaining for GAD at the electron microscopic level, (3H)-5-HT labeled nerve cells and terminals were not found to exhibit any significant immunoreactivity. Associations between (3H)-DA labeled and GAD immunoreactive processes with 5-HT immunoreactive or (3H)-5-HT-accumulating neurons, respectively, could also be observed in the NDM. When considered as a whole along with previous observations by other authors indicating a probable synthesis of 5-HT within NDM neurons, our data suggest that a given neuron can be classified as serotoninergic on the sole basis of its ability to selectively take up exogenous 5-HT under experimental conditions compatible with non interspecific labeling of catecholaminergic neurons. They also provide valuable information on the neurochemical environment and possible control of central serotoninergic neurons.

Animals↗
PubMed1986

Immunohistochemical evidence of plasticity of gamma-aminobutyric acid neurons in the red nucleus and adjacent reticular formation after contralateral cerebellectomy in the adult cat.

A comparative mapping of gamma-aminobutyric acid neurons identified by means of glutamic acid decarboxylase (GAD) immunohistochemistry was performed in the red nucleus (RN) in both intact and hemicerebellectomized adult cats (21 days postoperative). In the deafferented RN (contralateral to the lesion) as well as in the adjacent dorsolateral reticular formation, a marked increase in the number of GAD-positive perikarya was observed. In this mesencephalic area, some neurons may therefore increase their endogenous levels of immunodetectable GAD, as a response to cerebellar deafferentation. This can be viewed as one of the events contributing to functional recovery.

Animals↗
PubMed1986

Striatal neuropeptide Y neurones are under the influence of the nigrostriatal dopaminergic pathway: immunohistochemical evidence.

Selective unilateral 6-hydroxydopamine lesion of the nigrostriatal dopaminergic neurones in rats resulted, 12 to 90 days later, in a marked increase in the number of neuropeptide Y (NPY)-immunoreactive perikarya in the ipsilateral deafferented striatum compared to the contralateral intact side in the same animal and to both sides in control animals. The staining intensity of most positive cells also appeared to be enhanced in the deafferented striatum. These effects which can be interpreted as resulting from an increase in the intraneuronal levels of NPY may be accounted for by an increased production or a decreased metabolization of the peptide in the striatum deafferented from its dopaminergic input. The results therefore provide morphological evidence that the NPY-containing neuronal system of the striatum may undergo tonic influence from nigrostriatal dopaminergic afferents.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

Morphological evidence that serotonin-immunoreactive neurons in the nucleus dorsomedialis hypothalami could be under catecholaminergic influence.

In the nucleus dorsomedialis hypothalami (NDM), it has so far been possible to visualize serotonin (5-HT) neurons by 5-HT immunohistochemistry only after inhibition of the monoamine oxidase and loading with tryptophan. We report here that the intraventricular administration of dopamine, noradrenaline (NA) and adrenaline as well as isoproterenol and, to a lesser extent, apomorphine, similarly permitted 5-HT immunostaining of these neurons in pargyline-pretreated rats, and that additional pretreatment with propranolol prevented the NA-induced effect. Hence, it is proposed that the 5-HT content in the presumed serotoninergic neurons of the NDM could be under dopaminergic and/or beta-adrenergic receptor-mediated catecholaminergic influence.

Animals↗
PubMed1985

VIP neurons as prime synaptic targets for serotonin afferents in rat suprachiasmatic nucleus: a combined radioautographic and immunocytochemical study.

Cellular relationships between serotonin (5-HT) axon terminals and neurons containing vasoactive intestinal peptide (VIP) were characterized by combined radioautography and immunocytochemistry in rat suprachiasmatic nucleus (SCN). Light microscopic immunoradioautographs showed significant overlap between (3H)5-HT uptake sites and VIP-immunoreactive elements in the ventral half of the SCN. Of the 255 (3H)5-HT-labelled axonal profiles detected in a systematic electron microscopic survey of single thin sections from this area, 75 (30%) were directly apposed to VIP-immunoreactive nerve cell bodies and/or dendrites. Radioautographically labelled 5-HT varicosities often showed well-differentiated, symmetrical or asymmetrical synaptic junctions, 60% of which were established on VIP-immunoreactive nerve cell bodies or dendrites. In a separate sampling of 198(3H)5-HT-labelled terminals seen in apposition with VIP-immunoreactive elements, 50 showed a junctional complex at the site of contact. Postsynaptic immunoreactive elements were mostly dendrites but also included nerve cell bodies. Despite the methodological limitations inherent to the present double labelling approach, these data strongly support the view that VIP neurons are prime synaptic targets for 5-HT afferents in the SCN. VIP/5-HT interactions are thus likely to play an important functional role in this nucleus and may in particular subserve the 5-HT mediated regulation of certain circadian rhythms, including that of pituitary hormone secretion.

Afferent Pathways↗
PubMed1985

Glutamate decarboxylase-immunoreactive boutons in synaptic contacts with hypothalamic dopaminergic cells: a light and electron microscopy study combining immunocytochemistry and radioautography.

Double post-embedding immunolabeling of both tyrosine hydroxylase and glutamate decarboxylase on 1-micron semi-thin sections allowed the visualization of numerous endings that use gamma-aminobutyrate as a transmitter apposed to dopaminergic cell bodies in the periventricular-arcuate hypothalamic complex. Up to fifteen glutamate decarboxylase-positive contacts per tyrosine hydroxylase-positive cell profile could be observed. In some favourable planes of section glutamate decarboxylase-positive endings were also seen in close apposition to proximal dopaminergic dendrites. About 250 tyrosine hydroxylase-positive cell profiles, whose diameter approached the maximum diameter of the dopaminergic cells, were surveyed. An average of 7.4 glutamate decarboxylase-positive contacts were counted on these profiles. From these figures it was estimated that a dopaminergic cell body was contacted on average by 75-175 terminals that use gamma-aminobutyrate as a transmitter. At the electron-microscopic level, the nature of these contacts was investigated by a method combining radioautographic detection of cell bodies having taken up tritiated dopamine and pre-embedding immunostaining of glutamate decarboxylase containing endings. Glutamate decarboxylase-positive axon terminals were seen apposed to somatic and dendritic elements. On some favorable planes of section, they were found to be engaged in morphologically defined synaptic complexes of the symmetrical or asymmetrical type. A number of the postsynaptic perikarya were labelled by tritiated dopamine and, in agreement with the light microscopic observations, they were frequently seen in contact with more than one immunopositive ending. The present findings provide a morphological substratum for a direct gamma-aminobutyrate control of the tuberoinfundibular dopaminergic neurons. Such a control could account more particularly for the central, stimulatory effects of gamma-aminobutyrate on prolactin secretion.

Animals↗
PubMed1985

[Ultrastructural relations between monoaminergic and peptidergic systems in the hypothalamus. Radioautographic approach and immunocytochemical binding in the arcuate nucleus and suprachiasmatic nucleus in the rat].

This paper deals with the cytological substratum for interactions between serotonin and dopamine, pro-opiomelanocortin (POMC) or vasoactive intestinal peptide (VIP) within the hypothalamus. Using a combination of radioautography and immunocytochemistry on the same thin sections in the rat, direct appositions not involving synaptic specializations were demonstrated between serotoninergic terminals and dopaminergic as well as POMC neurons in the arcuate nucleus. In the suprachiasmatic nucleus, quantitative data have indicated that VIP neurons constitute a preferential synaptic target for serotoninergic afferents. The functional implications of these results are discussed.

Animals↗
PubMed1984

GABA neurons in the cat red nucleus: a biochemical and immunohistochemical demonstration.

Following unilateral kainic acid lesioning of neuronal cell bodies in the cat red nucleus (RN), a large decrease in glutamic acid decarboxylase (GAD) activity was detected in the injected RN, compared to the RN from control, non-injected animals. Using GAD immunohistochemistry, reactive perikarya were visualized dorsolaterally to the rostral part of the nucleus as well as within the RN proper. Taken together, these results point to the existence of an intrinsic GABAergic innervation in the RN area of the cat. The GABAergic neurons characterized here might thus correspond to the inhibitory interneurons previously detected electrophysiologically as a putative source of GABA for large-sized neurons of the RN.

Animals↗
PubMed1984

Ultrastructural relationships between serotonin and dopamine neurons in the rat arcuate nucleus and medial zona incerta: a combined radioautographic and immunocytochemical study.

Combined radioautographic and immunocytochemical detection of [3H]serotonin-labeled axon terminals and tyrosine hydroxylase-immunoreactive processes in the same thin sections allowed for electron microscopic demonstration of direct appositions between serotoninergic axonal varicosities and dopaminergic nerve cell bodies and/or dendrites in the anterior part of the arcuate nucleus and in the medial zona incerta. Although no junctional specializations were apparent at the sites of contacts, it is proposed that the observed appositions may represent a serotonin input onto tubero-infundibular and incerto-hypothalamic dopaminergic neurons. This innervation could account for some of the central neuroendocrine effects of serotonin, particularly its regulatory role on prolactin and gonadotropin secretion.

Animals↗
PubMed1983

In vitro radioautographic study of the monoaminergic innervation of cat red nucleus. Identification of serotoninergic terminals.

This study emphasizes the existence of a dense plexus of serotoninergic nerve terminals having specifically accumulated tritiated serotonin in vitro in the red nucleus of cat. These terminals innervate the whole rostrocaudal extension of the nucleus, being frequently in close apposition to the cell bodies and proximal dendrites of magnocellular neurons in its caudal part. A possible involvement of this serotoninergic input in the modulation of cerebello-rubro-spinal activity is proposed.

Animals↗
PubMed1983

Uptake and retention of [3H]adrenaline by central monoaminergic neurons: a light- and electron-microscope radioautographic study after intraventricular administration in the rat.

Paraventricular and paracisternal regions of adult rat central nervous system were investigated by light- and electron-microscope radioautography after intraventricular administration of tritiated adrenaline. In tissue primarily fixed by glutaraldehyde perfusion and post-fixed by immersion in osmium tetroxide, there were no aggregates of silver grains indicative of intraneuronal accumulation of the tracer, except over perivascular nerve terminals at the base of the brain. In contrast, when both fixation and postfixation were carried out by rapid vascular perfusion, preferentially labeled nerve cell bodies and axonal varicosities (i.e. terminals) were detected in various anatomical areas known to contain dopaminergic and/or noradrenergic neurons. Serotoninergic axonal varicosities in the supraependymal plexus and subcommissural organ, as well as a small group of nerve cell bodies of undetermined chemical identity in the n. paraventricularis thalami were also found to be labeled. Addition of a ten-fold higher concentration of non-radioactive serotonin to the solution of [3H]adrenaline suppressed the reactivity in the subcommissural organ and the supraependymal plexus but had no such effect elsewhere in brain. Lesioning of the nigrostriatal dopaminergic system with 6-hydroxydopamine prior to [3H]adrenaline injection eradicated axon terminal labeling in the ipsilateral neostriatum. Electron-microscopic examination of [3H]adrenaline-labeled varicosities in the neostriatum, lateral septum, arcuate nucleus and median eminence extended earlier observations on the ultrastructure of the catecholaminergic innervation of these regions. It was concluded that both dopaminergic and noradrenergic neurons as well as certain serotonin-containing axon terminals can take up and retain [3H]adrenaline, although they probably have lesser affinity for this amine than for their own transmitter. Due to the fact that presumptive adrenergic neurons are intermingled with dopaminergic and noradrenergic elements, further work will be needed to determine to which extent they also contributed to [3H]adrenaline uptake in the present experimental conditions.

Animals↗
PubMed1981

Immunocytochemical detection of peptides in osmicated and plastic-embedded tissue. An electron microscopic study.

In an attempt to improve the ultrastructural preservation of tissue immunostained with the postembedding staining technique, we verified the effect of postfixation with OsO4 on the antigenicity of several pituitary hormones and neuropeptides. For this purpose, the rat pituitary and central nervous system (CNS) were perfused with 2.5% glutaraldehyde and postfixed in two different ways: a) postfixation by immersion of small fragments in a mixture of 1% OsO4 and 1% potassium ferrocyanide, and b) postfixation with perfusion of 500 ml of 0.5% OsO4. The results obtained were similar with the two types of postfixation. In the pituitary gland, all the hormones could be very easily detected, although the staining was less intense for the glycoprotidic hormones. In the CNS the following neuropeptides: somatostatin, luteinizing hormone-releasing hormone (LHRH), Leu-enkephalin and substance P could be immunostained. These results indicate that a variety of polypeptidic antigens, including small neuropeptides, can survive postfixation with OsO4. In both the pituitary and CNS, the ultrastructural preservation was very good with a high contrast of membranes, thus permitting a clear identification of positive organelles. Moreover, it appears that, since the synaptic junctions are well-preserved after postfixation with OsO4, postembedding staining can now be utilized to identify and classify the different categories of endings containing neuropeptides.

Animals↗