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R M Bowker

Publications and source records attributed to R M Bowker.

At least 37 records · Page 2Linked to original sources
PubMed1990

Evoked changes in 5-hydroxytryptamine and norepinephrine release: in vivo dialysis of the rat dorsal horn.

Basal 5-hydroxytryptamine (5HT) and norepinephrine (NE) concentrations were measured in samples collected by in vivo dialysis of the rat dorsal horn. Infusion of KCl, glutamate, and NE by means of the dialysis probe increased NE, but decreased 5HT extracellular concentrations. In contrast, electrical stimulation of the nucleus raphe magnus increased the recovery of both NE and 5HT. These findings suggest differential regulation of noradrenergic and serotonergic nerve terminals modulating nociceptive neurotransmission within the dorsal horn.

Anesthesia↗
PubMed1990

Descending modulation of dorsal horn biogenic amines as determined by in vivo dialysis.

Bipolar concentric stimulating electrodes were placed medially within the nucleus raphe magnus and laterally within the nucleus gigantocellularis. The levels of norepinephrine (NE), serotonin (5-HT), and 5-hydroxyindolacetic acid (5-HIAA) within the dorsal horn of the spinal cord were measured before and after electrical stimulation of these brainstem nuclei using in vivo dialysis coupled with high pressure liquid chromatography and electrochemical detection. Stimulation medially significantly increased the levels of all three amines. While simulation laterally also increased NE, both 5-HT and 5-HIAA were significantly reduced. The relevance of these findings to descending modulation of ascending nociceptive neural activity within the dorsal horn is discussed.

Animals↗
PubMed1990

Damage to bulbospinal serotonin-, tyrosine hydroxylase-, and TRH-containing axons occurs early in the development of experimental allergic encephalomyelitis in rats.

Spinal cord monoaminergic and peptidergic axonal damage occurring during the development of experimental allergic encephalomyelitis (EAE) was assessed using immunohistochemistry. Spinal cord axons immunoreactive for serotonin, catecholamines, or a thyrotropin-releasing hormone marker peptide were found to be markedly swollen and distorted by the earliest stage of detectable paralysis during EAE development (the flaccid tail stage). As clinical signs progressed to complete hindlimb paralysis, axonal damage became increasingly extensive. Axonal damage was equally pronounced whether EAE was induced by inoculation with purified myelin basic protein or with whole spinal cord homogenate, suggesting that the damage did not result from an immune attack directed against specific monoaminergic and/or peptidergic antigens present in the inoculant. However, two observations suggested that mechanical or chemical factors associated with the inflammatory foci contribute to the axonal damage: first, distorted axons were nearly always located adjacent to blood vessels or the pial surface, sites at which inflammation occurs during EAE. Second, the severity of axonal damage correlated with the severity of the inflammation. The early onset of axonal damage during development of EAE and the close correlation that was found between the severity of axonal damage and the severity of clinical signs suggested that the axonal damage may contribute to the clinical signs of the disease.

Animals↗
PubMed1988

Distribution of mu-opioid receptors in the nucleus raphe magnus and nucleus gigantocellularis: a quantitative autoradiographic study.

The present study has described and quantitated the distribution of mu-opioid receptors in the nucleus raphe magnus (NRM) and nucleus gigantocellularis (NGC), using in vitro autoradiography. Moderately dense binding of a mu-enkephalin analog, DAGO, was observed in the NRM and adjacent parts of the NGC. DAGO binding density was greatest in the anterior NRM, possibly due to a greater involvement in the descending, opiate-mediated modulation of nociception. These findings agree with proposed roles for this region in the central regulation of pain.

Animals↗
PubMed1988

The origins and trajectories of somatostatin reticulospinal neurons: a potential neurotransmitter candidate of the dorsal reticulospinal pathway.

Somatostatin (SOMA)-immunoreactive neurons present in the nucleus gigantocellularis and nucleus raphe magnus formed the origins of a descending pathway from the rostral medulla to the spinal cord. This descending pathway was traced through the central medullary tegmentum and dorsolateral funiculus to innervate the dorsal horn. The location, trajectories and presumed inhibitory nature of SOMA in the spinal cord suggest that SOMA maybe a potential neurotransmitter candidate for the classic dorsal reticulospinal pathway.

Animals↗
PubMed1988

Retrograde transport of horseradish peroxidase is specifically impaired in bulbospinal serotonin axons during experimental allergic encephalomyelitis.

Bulbospinal monoamine-containing axons appear to be severely damaged in rats with the inflammatory and demyelinating disease, experimental allergic encephalomyelitis (EAE). This paper reports that although bulbospinal serotonin axons are damaged in the disease, cell bodies of origin in the medulla oblongata retain normal morphology. However, these serotonin cells are not able to retrogradely transport the enzyme horseradish peroxidase (HRP) from terminals in the lumbar spinal cord. Most non-serotonin-containing cells in the medulla which project to the lumbar spinal cord retain the ability to retrogradely transport HRP from the lumbar cord during the disease. These findings suggest that there is some specificity to spinal cord axonal damage during EAE.

Animals↗
PubMed1987

Evidence for the co-localization of somatostatin- and methionine-enkephalin-like immunoreactivities in raphe and gigantocellularis nuclei.

Somatostatin-like and methionine-enkephalin-like immunoreactivities were co-localized in neurons in the raphe nuclei and the nucleus gigantocellularis among immunoreactive cells stained for either one of these putative neurotransmitters. Their colocalization suggests that they form a subset of these two peptide populations and may serve as a major inhibitory system within the medullary reticular nuclei.

Animals↗
PubMed1987

Serotonergic and non-serotonergic raphe neurons projecting to the feline lumbar and cervical spinal cord: a quantitative horseradish peroxidase-immunocytochemical study.

A quantitative study of raphe-spinal neurons and serotonergic neurons in 3 medullary raphe nuclei in the cat indicates that more than 80% of the raphe-spinal neurons that project to the spinal cord are serotonergic raphe-spinal neurons in each of the nuclei. More than 85% of the descending raphe-spinal neurons in the two caudal nuclei, nucleus raphe pallidus and nucleus raphe obscurus, are serotonergic, whereas 75% of the raphe-spinal neurons in the more rostrally placed nucleus raphe magnus contain serotonin (5-HT). These results are discussed in relation to descending systems containing both neuropeptides and 5-HT and collateralizing to several spinal segments.

Animals↗
PubMed1987

Differential labeling of the vestibular complex following unilateral injections of horseradish peroxidase into the cat and rat locus coeruleus.

Following unilateral injections of horseradish peroxidase into the cat and rat locus coeruleus (LC), bilateral retrograde labeling was evident in all 4 vestibular nuclei. In both species, the major contributions of LC afferents arose from the ipsilateral rather than the contralateral vestibular nuclei. Quantitative analysis in the rat has indicated that approximately 90% of the total vestibular-LC projections originated from the ipsilateral vestibular nuclear complex, with 10% from the contralateral. The frequency distribution was in the order of lateral greater than medial greater than superior greater than inferior vestibular nuclei.

Animals↗
PubMed1986

The relationship between descending serotonin projections and ascending projections in the nucleus raphe magnus: a double labeling study.

The nucleus raphe magnus and rostral parts of the nucleus raphe obscurus were found to have extensive efferent projections: a major ascending non-serotonergic (5-HT) projection through the median forebrain bundle, and a descending system consisting of both 5-HT and non-5-HT neurons. Differences in the localizations of their cells of origin suggest that they form two distinct efferent systems from the caudal medullary raphe nuclei.

Animals↗
PubMed1986

Serotonergic and peptidergic inputs to the primate ventral spinal cord as visualized with multiple chromagens on the same tissue section.

Primate spinal cord tissue sections were sequentially incubated in serotonin (5-HT), substance P (SP) and methionine-enkephalin antisera and reacted immunocytochemically. The findings indicate that virtually all SP-like immunoreactivity coexists with 5-HT in the ventral horn, while an additional group of 5-HT terminals do not contain SP immunoreactivity.

Animals↗
PubMed1986

Intrinsic 5HT-immunoreactive neurons in the spinal cord of the fetal non-human primate.

Serotonin (5HT) immunoreactive neurons were identified in the late-term fetal spinal cord of normal non-human primates. These neurons were distributed throughout the spinal cord, being concentrated in lamina X and the subjacent ventral median fissure, while their immunoreactive fibers and terminals innervated the zone surrounding the central canal and the ventral spinal artery. Even at this late fetal stage, the dorsal and ventral spinal gray matter was virtually devoid of any positive 5HT immunoreactivity, in contrast to that seen in the adult primate. These findings suggest that the intrinsic 5HT neurons of the primate during development may modulate CSF composition or provide cues for spinal cord differentiation rather than regulate sensorimotor functions as they do in the adult.

Animals↗
PubMed1985

Variability in the characteristics of pontogeniculooccipital spikes during paradoxical sleep.

An important criterion for identifying paradoxical sleep is the presence of a peculiar waveform recorded in the pons, lateral geniculate body, and visual cortex during that sleep state. These waveforms, termed PGO waves, have long been viewed as having large and constant amplitudes, an initial negative deflection in the visual cortex, and not being dependent on the levels of background illumination. Waveforms recorded during wakefulness have different characteristics, and these have been used to differentiate the waking state from paradoxical sleep. The present study demonstrated that most PGO waves have highly variable amplitudes during paradoxical sleep and that only a small fraction conform to the stereotypic wave characteristics of constant and large amplitudes and the presence of initial negative deflections. These findings argue against the criteria commonly used to differentiate PGO waves during paradoxical sleep from the eye movement potentials recorded in wakefulness.

Animals↗
PubMed1984

Origins and terminations of descending noradrenergic projections to the spinal cord of monkey.

This report describes the distribution of noradrenergic cells in the brainstem and the pattern of terminal varicosities in the spinal cord of monkey using the immunocytochemical localization of dopamine-beta-hydroxylase (DBH). Using two separate and equally reliable techniques, retrograde transport of the antibody to DBH and a double-labeling method, the cells of origin of noradrenergic fibers in the spinal cord have been identified. The results of these studies indicate that 79% of all noradrenergic cells with axons projecting to the spinal cord are located in the nucleus subcoeruleus and nucleus locus coeruleus. Other pontine noradrenergic cell groups contribute the remainder of the fibers to the cord. No medullary cells contribute to the noradrenergic innervation of the spinal cord.

Animals↗
PubMed1983

Descending serotonergic, peptidergic and cholinergic pathways from the raphe nuclei: a multiple transmitter complex.

The localization of serotonergic, various peptidergic and possibly cholinergic neurons in the medullary raphe nuclei that project to the lumbosacral spinal cord have been studied using a retrograde transport method combined with immunocytochemical and histochemical techniques. Spinally projecting neurons stained for serotonin-like, substance P-like, enkephalin-like and thyrotropin-releasing hormone-like immunoreactivity and for the histochemical marker acetylcholinesterase were all observed in each of the raphe nuclei of the medulla, as well as in the adjacent ventrolateral reticular formation. The similar distributions of the descending serotonergic and peptidergic neurons in the raphe nuclei as well as quantitative data on their relative numbers suggest that a large fraction of raphe-spinal neurons contain serotonin co-existing with one or more peptides in the same cell.

Acetylcholine↗
PubMed1983

Noradrenergic projections to the spinal cord of the rat.

Noradrenergic terminals were identified in the spinal cord of rats by immunocytochemical staining for dopamine-beta-hydroxylase. Although immunoreactive fibers and terminals were observed throughout the spinal grey matter, heavier accumulations of terminal labeling were observed in the marginal layer of the dorsal horn, in the ventral horn among motoneurons, and in the autonomic lateral cell columns of the thoracic and sacral spinal cord. Two specific retrograde transport techniques were employed to identify the origins of these noradrenergic terminations in the spinal cord. Cells of origin were observed in the locus coeruleus, the subcoeruleus, the medial and lateral parabrachial, and the Kölliker-Fuse nuclei, as well as adjacent to the superior olivary nucleus. These regions correspond to the A5-A7 cell groups of the pons. No spinally projecting noradrenergic cells were ever observed in the medulla. It was concluded that pontine noradrenergic cell groups are the sole source of noradrenergic terminals in the spinal cord.

Animals↗