Biomedical subjects

S L Dun

Publications and source records attributed to S L Dun.

At least 37 records · Page 2Linked to original sources

PubMed1996

Hyperalgesia induced by pituitary adenylate cyclase-activating polypeptide in the mouse spinal cord.

The aim of the present study was to evaluate the distribution of pituitary adenylate cyclase-activating polypeptide (PACAP)-like immunoreactivity in the mouse spinal cord using an antibody against PACAP38 and to determine the behavioral profile, particularly with respect to hyperalgesia, of PACAP38 given intrathecally (i.t.) in the mouse. Immunoreactivity to PACAP38 was detected in numerous nerve fibers in the superficial layers of the dorsal horn of cervical, thoracic, lumbar and sacral segments and a few fibers extended into the deeper layers of the spinal cord. In addition, PACAP-like immunoreactivity were seen in the intermediolateral cell column of the thoracic and sacral segments. In behavioral studies, PACAP38 (0.05-0.5 microgram) produced a dose-dependent decrease of the tail-flick latency when given i.t. in the mouse. At higher doses (1-10 micrograms), PACAP38 given i.t. elicited biting and scratching behaviors lasting 10-20 min after the injection. PACAP at high doses (1-10 micrograms) also produced licking at tail, paw and penis and intense grooming behaviors immediately after the i.t. injection. Similar to substance P, these behaviors produced by PACAP can be considered as pain-like syndrome. These findings suggest that PACAP may be a sensory neurotransmitter involved in nociceptive signalling in the mouse spinal cord.

Animals↗

PubMed1996

The synaptic structure of PACAP immunoreactive axons in the intermediolateral nucleus of the rat.

Immuno-electronmicroscopic studies were performed to detect the presence and features of synaptic contacts between pituitary adenylate cyclase activating polypeptide immunoreactive (PACAP-ir) axons and cholera toxin B-horseradish peroxidase labeled preganglionic sympathetic neurons (PSNs) in the intermediolateral nucleus of the rat thoracic spinal cord. PACAP-ir axon varicosities, which contained small clear and large core synaptic vesicles, were found to form asymmetric type of synaptic contacts with dendrites and infrequently with somata of labeled preganglionic neurons. The present study provides ultrastructural evidence of PACAP-ir synaptic contacts with PSNs, raising the possibility that the peptide may function as a transmitter/modulator to these neurons.

Animals↗

PubMed1996

Pituitary adenylate cyclase activating polypeptide-immunoreactivity in human spinal cord and dorsal root ganglia.

Immunohistochemical studies using an antibody against pituitary adenylate cyclase activating polypeptide-38 (PACAP) were performed on spinal cords and dorsal root ganglia harvested from two human cadavers. PACAP-like immunoreactivity (PACAP-LI) was detected in nerve fibers of the superficial layers of the dorsal horn, a few of which extended into the deeper laminae and as far as the ventral horn. At the thoracic segments, additional PACAP-LI nerve fibers were seen in the lateral funiculus projecting into the intermediolateral cell column. Dorsal root ganglia contained numerous PACAP-LI cell bodies of varying intensity. As a control, immunoreactivity to calcitonin gene-related peptide (CGRP) and substance P(SP) was also studied and found to be in nerve fibers of the substantia gelatinosa of the dorsal horn and in dorsal root ganglion cells. These results show that the pattern of distribution of PACAP-LI in the human spinal cord and dorsal root ganglia is similar to that of rodents and further suggest that PACAP may participate in sensory and autonomic functions.

Calcitonin Gene-Related Peptide↗

PubMed1996

Pituitary adenylate cyclase activating polypeptide-immunoreactive sensory neurons innervate rat adrenal medulla.

Rat adrenal chromaffin cells were invested by a dense network of nerve fibers immunoreactive to pituitary adenylate cyclase activating polypeptide-38 (PACAP-IR). Immunohistochemical studies demonstrated the presence of PACAP-IR in nodose and dorsal root ganglion cells, but not in neurons of the intermediolateral cell column and other autonomic nuclei of the thoracic and upper lumbar spinal cord. Somata of the T7 to T12 paravertebral ganglia were PACAP-negative. A few lightly labeled neurons were occasionally noted in the dorsal motor nucleus of the vagus. Injection of the retrograde tracer Fluorogold into the left adrenal medulla 3 days prior to sacrifice resulted in the labeling of a population of neurons in the ipsilateral spinal cord intermediolateral cell column (T1 to L1), ipsilateral and contralateral nodose ganglia and ipsilateral dorsal root ganglia from T7 to T10 inclusive. A small number of lightly labeled somata was occasionally noted in the dorsal motor nucleus of the vagus. Combined retrograde tracing and PACAP immunohistochemistry showed that a population of Fluorogold-containing nodose and dorsal root ganglion cells were also PACAP-positive. Pre-treatment of the rats with capsaicin caused a marked reduction of the PACAP-IR in the adrenal gland as well as in the superficial layers of the dorsal horn and caudal spinal trigeminal nucleus. These findings, in conjunction with the apparent absence of PACAP-IR in spinal sympathetic preganglionic neurons, sympathetic postganglionic neurons, and dorsal motor nucleus of the vagus, raise the possibility that PACAP-IR fibers observed in the adrenal medulla are primarily sensory in origin. As a corollary, catecholamine secretion from chromaffin cells may be modulated by the peptidergic sensory afferents in addition to the cholinergic sympathetic preganglionic nerve fibers.

Adrenal Medulla↗

PubMed1995

Infrequent co-existence of nitric oxide synthase and parvalbumin, calbindin and calretinin immunoreactivity in rat pontine neurons.

Neurons in the laterodorsal tegmental nucleus (LDTg), ventrolateral dorsal tegmental nucleus (LDTgV), pedunculopontine tegmental nucleus (PPTg), lateral and medial parabrachial nuclei (LPB and MPB) were immunoreactive to brain nitric oxide synthase (NOS) or isoform I. Double-labeling experiments showed that very few NOS-containing neurons in the pons were immunoreactive to any of the three calcium-binding proteins: calbindin-D 28K (CB-IR), parvalbumin (PV-IR) and calretinin (CR-IR). These findings extend our previous observation in the neocortex and suggest that a population of central NOS-containing neurons can be neurochemically characterized as CB/CR/PV deficient.

Amino Acid Oxidoreductases↗

PubMed1995

Nitric oxide synthase-immunoreactive vagal afferent fibers in rat superior cervical ganglia.

Chronic (5-14 days) preganglionic denervation of the rat superior cervical ganglia by sectioning the cervical sympathetic trunk resulted in a time-related partial or complete loss of nitric oxide synthase (isoform I)-immunoreactive fibers and terminals surrounding many sympathetic ganglionic neurons. Unexpectedly, denervation unmasked many varicose nitric oxide synthase-immunoreactive fibers, some of which could be traced the entire length of the superior cervical ganglia. Injection of the retrograde tracer Fluorogold into the superior cervical ganglia labeled a population of nodose ganglion cells and of dorsal root ganglion cells from C8 to T3 segments. When the same sections were processed for nitric oxide synthase-immunoreactivity, 40% of the Fluorogold-containing nodose ganglion cells also expressed nitric oxide synthase-immunoreactivity, whereas colocalization was observed in only a few dorsal root ganglion cells. Similarly, injection of Fluorogold into denervated superior cervical ganglia labeled a population of nodose ganglion cells. Sectioning of all nerve trunks associated with the superior cervical ganglion prior to injection of Fluorogold, except the cervical sympathetic trunk, resulted in no detectable labeling of Fluorogold in the ipsilateral nodose ganglion cells. These results indicate that a population of rat nodose ganglion cells contain nitric oxide synthase and that some of these neurons project their axons through the superior cervical ganglion and terminate in the peripheral target tissues. The possibility that nitric oxide synthase-immunoreactive vagal afferent fibers may participate in nociception is considered.

Afferent Pathways↗

PubMed1994

Infrequent co-localization of nitric oxide synthase and calcium binding proteins immunoreactivity in rat neocortical neurons.

Immunoreactivity to nitric oxide synthase (NOS-IR) was detected in a small population of rat neocortical neurons scattered throughout the frontal, parietal, temporal and occipital cortices. Two-color double-labeling studies revealed that the number of NOS-IR neocortical neurons expressing immunoreactivity to the calcium binding proteins parvalbumin (PV-IR), calbindin-D28K (CB-IR) or calretinin (CR-IR), was low. The absence or low level of calcium binding proteins may imply a reduced Ca2+ buffering capacity in NOS-containing neurons, thereby contributing to their vulnerability to Ca2+ influx through the activated AMPA/kainate receptors reported by others.

Amino Acid Oxidoreductases↗

PubMed1994

c-fos antisense attenuates Fos expression in rat central neurons induced by hemorrhage.

Hemorrhage caused by withdrawing 3-4 cm3 of blood from adult rats over a period of 1-2 h induced the expression of Fos proteins, which were detected by immunocytochemical methods in neurons of the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei, area postrema, nucleus of the solitary tract (NTS), ventrolateral medulla (VLM) and in intermediolateral cell column (IML) of the spinal cord. Daily intraventricular (i.c.v.) injections of c-fos antisense (50 nmol 5 microliters -1) for 2 days prior to hemorrhage markedly attenuated the extent and intensity of Fos-immunoreactivity (FOS-IR) compared with that of rats injected with c-fos sense in the areas mentioned above. The results indicate the effectiveness of i.c.v. administration of c-fos antisense in blocking Fos expression in central neurons following hemorrhage.

Animals↗

PubMed1994

Colocalization of nitric oxide synthase and somatostatin immunoreactivity in rat dentate hilar neurons.

Distribution of nitric oxide synthase (NOS), somatostatin (SSN), and parvalbumin (PV) was studied in the rat hippocampus by immunohistochemical methods. The aim was to explore the interrelationship between SSN-immunoreactive (SSN-IR) neurons in the dentate hilus, which have been shown to be vulnerable to a number of pathophysiological insults, and the presence or absence of NOS and/or PV in the same subset of dentate hilar neurons. Small NOS-IR neurons were scattered in the pyramidal, oriens, and radiatum layers of the CA1-CA3 areas and in the subiculum, where larger NOS-IR neurons were occasionally noted. In the area dentata, NOS-IR neurons, which were composed of small and large polymorphic cells, appeared as a single file at the hilar border with the granule cell layer and clustered in the hilus in fairly high density. Double-labeling techniques showed that most NOS-IR neurons in the hilus were SSN-IR, whereas coexistence of NOS and PV immunoreactivity or SSN and PV immunoreactivity was low in dentate hilar neurons. In other areas of the hippocampus, colocalization of NOS and SSN in the same neurons was much less frequent. Thus, SSN-IR neurons in the dentate hilus constitute a population of neurons that contain the enzyme NOS as well. The presence of NOS coupled to the lack or low level of PV in this group of neurons may provide a neurochemical basis for their high susceptibility to certain pathophysiological insults.

Amino Acid Oxidoreductases↗

PubMed1994

Nitric oxide synthase immunoreactivity in rat pontine medullary neurons.

Nitric oxide synthase immunoreactivity was detected in neurons and fibers of the rat pontine medulla. In the medulla, nitric oxide synthase-positive neurons and processes were observed in the gracile nucleus, spinal trigeminal nucleus, nucleus of the solitary tract, dorsal motor nucleus of the vagus, nucleus ambiguus, medial longitudinal fasciculus, reticular nuclei and lateral to the pyramidal tract. In the pons, intensely labeled neurons were observed in the pedunculopontine tegmental nucleus, paralemniscal nucleus, ventral tegmental nucleus, laterodorsal tegmental nucleus, and lateral and medial parabrachial nuclei. Labeled neurons and fibers were seen in the interpeduncular nuclei, dorsal and median raphe nuclei, central gray and dorsal central gray, and superior and inferior colliculi. Double-labeling techniques showed that a small population (< 5%) of nitric oxide synthase-positive neurons in the medulla also contained immunoreactivity to the aminergic neuron marker tyrosine hydroxylase. The majority of nitric oxide synthase-immunoreactive neurons in the dorsal and median raphe nuclei were 5-hydroxytryptamine-positive, whereas very few 5-hydroxytryptamine-positive cells in the caudal raphe nuclei were nitric oxide synthase-positive. Virtually all nitric oxide synthase-positive neurons in the pedunculopontine and laterodorsal tegmental nuclei were also choline acetyltransferase-positive, whereas nitric oxide synthase immunoreactivity was either low or not detected in choline acetyltransferase-positive neurons in the medulla. The results indicate a rostrocaudal gradient in the intensity of nitric oxide synthase immunoreactivity, i.e. it is highest in neurons of the tegmentum nuclei and neurons in the medulla are less intensely labeled. The majority of cholinergic and serotonergic neurons in the pons are nitric oxide synthase-positive, whereas the immunoreactivity was either too low to be detected or absent in the large majority of serotonergic, aminergic and cholinergic neurons in the medulla.

Amino Acid Oxidoreductases↗

PubMed1993

Nitric oxide synthase immunoreactivity in rat superior cervical ganglia and adrenal glands.

Nitric oxide synthase-immunoreactivity (NOS-IR) was detected in strands of nerve fibers entering the rat superior cervical ganglia (SCG) and in nerve fibers forming a plexus beneath the capsule of adrenal glands. Within the SCG, varicose NOS-IR fibers encircled virtually all postganglionic neurons and small diameter cells, presumably small intensely fluorescent (SIF) cells. Perikarya of SIF cells exhibited strong NOS-IR, whereas the level appeared to be low in postganglionic neurons. Decentralization of the SCG for 4-6 days markedly reduced the number as well as the intensity of NOS-IR fibers without causing a detectable change of NOS-IR in the postganglionic neurons and SIF cells. Beneath the adrenal capsule, bundles of NOS-IR fibers bifurcated and made a sharp turn to reach the adrenal medulla. Chromaffin cells, which themselves exhibited fairly strong NOS-IR, appeared to be surrounded by NOS-IR fibers. The result shows that NOS-IR is present in pre- and post-synaptic elements of the sympathetic ganglia and adrenal medulla, representing a complex system that may regulate the activity of ganglionic neurons and chromaffin cells via a number of sites of action.

Adrenal Glands↗

PubMed1993

Hemorrhage induces Fos immunoreactivity in rat medullary catecholaminergic neurons.

In urethane anesthetized rats one hour after lowering the systolic blood pressure to 70-75 mmHg by withdrawing 3-4 ml of blood, Fos immunoreactivity (Fos-IR), confined to the cell nucleus, was detected bilaterally in numerous cells of the nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM). A few Fos-IR neurons were observed in the lateral reticular nucleus, dorsal medullary reticular nucleus, spinal trigeminal nucleus, medial inferior olive, interfasciculus hypoglossi and paramedian rostral medulla. In sham-operated animals, a much smaller number of Fos-IR neurons were scattered in the NTS, VLM and other nuclei mentioned above. Double labeling with antisera to tyrosine-hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT) showed that 60% of TH-positive neurons in the NTS contained Fos-IR, and 70-80% of TH-positive neurons in the caudal VLM and 50-60% of PMNT-positive neurons in the rostral VLM expressed Fos-IR. Only a few TH- or PNMT-positive neurons in the C2, C3 (paramedian rostral medulla) areas and within the medial longitudinal fasciculus were Fos-IR. About 40% of PNMT/Fos-IR neurons in the rostral VLM contained the retrograde tracer fluorogold, which was injected (< 1 microliter) into the white matter dorsolateral to the intermediolateral cell column of T2-T3 segments 2 to 3 days prior to hemorrhagic experiments. Very few TH-positive neurons in the caudal VLM contained fluorogold. Finally, clusters of Fos-IR neurons, which also labeled with antisera to choline acetyltransferase, were detected in the intermediolateral cell column of the spinal cord. The results indicate that during hemorrhage aminergic neurons in the caudal and rostral VLM and in the NTS are activated insofar as c-fos expression is concerned. As a corollary, the monoaminergic neurons in the medulla constitute an essential component in the ascending as well as descending reflex pathway involved in the adjustment of cardiovascular dynamics during hemorrhage.

Animals↗

PubMed1993

Nitric oxide synthase immunoreactivity in the rat, mouse, cat and squirrel monkey spinal cord.

The distribution of nitric oxide synthase-immunoreactive neurons was examined in the spinal cord of rats, mice, cats and squirrel monkeys at the light microscopic level. Some sections were processed for choline acetyltransferase immunoreactivity. Double-labeling techniques were used to assess possible co-localization of nitric oxide synthase and choline acetyltransferase immunoreactivity in the same spinal neurons. Nitric oxide synthase-immunoreactive neurons were concentrated in three fairly well-defined regions of the spinal cord of all species studied: (i) the intermediolateral cell column of the thoracic and sacral segments, (ii) lamina X of all segments, and (iii) the superficial layers of the dorsal horn of all segments. A few nitric oxide synthase-immunoreactive neurons were scattered in the deeper laminae and the ventral horn. There were fewer nitric oxide synthase-positive neurons in monkey spinal lamina X and dorsal horn than in similar locations of rodents and felines. Double-staining showed that not all choline acetyltransferase-positive neurons in the intermediate cell column and lamina X were nitric oxide synthase-immunoreactive. In the ventral horn, choline acetyltransferase-positive neurons (presumed motoneurons) were nitric oxide synthase-negative. In addition to cell bodies, nitric oxide synthase-positive fibers were scattered in the dorsal, lateral and ventral horns of all species. Finally, punctate nitric oxide synthase-immunoreactive fibers were seen traversing the dorsal, lateral and ventral white matter, and reaching the respective gray matter. The present study shows that, in spite of quantitative differences, the pattern of distribution of nitric oxide synthase-positive neurons in the spinal cord was similar across the four species. The concentration of nitric oxide synthase-positive neurons in the autonomic nuclei and laminae I, II and X of all four species underscores a prominent role of these neurons in visceral and sensory functions.

Amino Acid Oxidoreductases↗

PubMed1992

Nitric oxide synthase immunoreactivity in rat spinal cord.

Immunoreactivity to nitric oxide synthase (NOS-IR) and choline acetyltransferase (ChAT-IR) was detected in the adult rat spinal cord using the avidin-biotin-peroxidase technique. Intensely stained NOS-positive neurons with cell processes were observed in the intermediolateral cell column of the thoracic and sacral segments and around the central canal of all segments. These areas also contained ChAT-IR neurons. A number of small- to medium-sized NOS-IR cells were noted in the superficial and deeper laminae throughout the entire cord. NOS-IR was not detected in the ventral horn motoneurons, which were, however, ChAT-IR. The results indicate that NOS-IR is present in autonomic preganglionic neurons and in selected neurons in the dorsal horn and lamina X, but appears to be absent in motoneurons.

Amino Acid Oxidoreductases↗

PubMed1992

Hypotension preferentially induces c-fos immunoreactivity in supraoptic vasopressin neurons.

Immunoreactivity to Fos protein (Fos-IR) was detected in rat hypothalamic neurons within 1 h of onset of hemorrhage by withdrawing 4-5 ml of blood, which lowered the arterial blood pressure to 50-70 mm Hg. About 70% of vasopressin (AVP)-containing neurons in the supraoptic nucleus (SON) and 20% in the paraventricular nucleus (PVN) expressed Fos-IR. In contrast, 5% of oxytocin (OXY)-containing neurons in the SON and < 1% in PVN were Fos-IR. Intravenous infusion of the vasodilating agent, nitroprusside, which lowered the blood pressure to levels comparable to that attained by hemorrhage, induced Fos-IR in greater than 65% of AVP-containing neurons in the SON, while relatively few AVP neurons in the PVN were Fos positive. These results suggest that hemorrhage or hypotension preferentially induces c-fos expression in supraoptic AVP-containing neurons.

Animals↗

PubMed1992

Hypovolemia induces Fos-like immunoreactivity in neurons of the rat supraoptic and paraventricular nuclei.

Immunoreactivities to Fos proteins were detected in numerous neurons in the supraoptic, paraventricular and accessory neurosecretory nuclei 1 h following withdrawal of 4-5 cc of blood from the rat femoral arteries. Few or no positive cells were observed in the same nuclei in sham-operated or control animals. It is concluded that hypovolemia induces c-fos expression in hypothalamic neurons known to be associated with blood volume/pressure regulation.

Animals↗

PubMed1992

Synaptic mechanisms in sympathetic preganglionic neurons.

Intracellular recordings from sympathetic preganglionic neurons (SPNs) in adult cat and neonatal rat spinal cord slices reveal four types of synaptic potentials, namely, excitatory postsynaptic potentials (EPSPs), inhibitory postsynaptic potentials (IPSPs), and slow EPSPs in both preparations, and a slow IPSP in cat SPNs. Pharmacological studies show that glutamate or a related excitatory amino acid and glycine are the probable mediators of EPSPs and IPSPs. There may be heterogenous mediators of slow EPSPs; substance P, serotonin, norepinephrine, and epinephrine are all probable mediators of slow EPSPs in subpopulations of SPNs. In the case of slow IPSPs, norepinephrine appears to be the likely transmitter. Finally, stimulation of ventral roots elicits a synaptic potential that appears to be caused by glutamate released from afferent fibers in the ventral roots. Our results indicate that a multitude of synaptic mechanisms exist in the rat SPNs by means of which inputs arising from sensory and supraspinal neurons are processed in a timely and orderly manner, thus ensuring highly organized but differentiated outputs to multiple peripheral target cells.

Animals↗

PubMedDate not supplied

Endomorphins: localization, release and action on rat dorsal horn neurons.

Endomorphin (Endo) 1 and 2, two tetrapeptides isolated from the bovine and human brain, have been proposed to be the endogenous ligand for the mu-opiate receptor. A multi-disciplinary study was undertaken to address the issues of localization, release and biological action of Endo with respect to the rat dorsal horn. First, immunohistochemical studies showed that Endo-1- or Endo-2-like immunoreactivity (Endo-1- or Endo-2-LI) is selectively expressed in fiber-like elements occupying the superficial layers of the rat dorsal horn, which also exhibit a high level of mu-opiate receptor immunoreactivity. Second, release of immunoreactive Endo-2-like substances (irEndo) from the in vitro rat spinal cords upon electrical stimulation of dorsal root afferent fibers was detected by the immobilized antibody microprobe technique. The site of release corresponded to laminae I and II where the highest density of Endo-2-LI fibers was localized. Lastly, whole-cell patch clamp recordings from substantia gelatinosa (SG) neurons of rat lumbar spinal cord slices revealed two distinct actions of exogenous Endo-1 and Endo-2: (1) depression of excitatory and/or inhibitory postsynaptic potentials evoked by stimulation of dorsal root entry zone, and (2) hyperpolarization of SG neurons. These two effects were prevented by the selective mu-opiate receptor antagonist beta-funaltrexamine. The localization of endomorphin-positive fibers in superficial layers of the dorsal horn and the release of irEndo upon stimulation of dorsal root afferents together with the observation that Endo inhibits the activity of SG neurons by interacting with mu-opiate receptors provide additional support of a role of Endo as the endogenous ligand for the mu-opiate receptor in the rat dorsal horn.

Afferent Pathways↗