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Biomedical subjects

H Sann

Publications and source records attributed to H Sann.

At least 55 records · Page 3Linked to original sources
PubMed1995

Choline acetyltransferase-immunoreactive neurones in a prevertebral sympathetic ganglion, the inferior mesenteric ganglion.

Using immunohistochemical techniques a small population of choline acetyltransferase (ChAT) immunoreactive (IR) neurones has been identified in the inferior mesenteric ganglion (IMG) of guinea pig (4.6% of all neurones), ferret (6.4%) and rat (0.4%). A detailed study in the guinea-pig IMG revealed that the vast majority of cholinergic neurones did not express tyrosine hydroxylase (TH)-IR, indicating that they were non-catecholaminergic. The cholinergic neurones were significantly larger than the TH-positive neurones. The majority of the ChAT-IR cells (64%) was observed in small clusters which were consistently located in the caudal lobe of the IMG close to the entry of the hypogastric nerves. 83% of the ChAT-IR cells also contained neuropeptide Y (NPY). Since the vast majority of TH-negative cells were ChAT-positive (94%), the TH negativity was taken as an indirect indication for ChAT-IR. NPY-IR, somatostatin (SOM)-IR and vasoactive intestinal peptide (VIP)-IR were found in both the TH-IR cells (22, 84 and 1%, respectively) and the putative cholinergic population (95, 84 and 70, respectively). Thus the majority of cholinergic neurones in the IMG were likely to contain NPY, SOM and VIP. TH-IR cells exhibited an extensive innervation of fibers immunoreactive for ChAT, VIP, ENK and NOS. In contrast, only a sparse plexus of ChAT-, ENK-, NOS-, NPY- and SOM-positive fibres was found around the TH-negative cells. VIP-IR fibres did not appear to innervate ChAT neurones.

Animals↗
PubMed1995

Reduction of substance P binding sites in the spinal dorsal horn after perineural capsaicin treatment in the rat.

The long-term effect of perineural capsaicin treatment on the distribution of substance P (SP) binding sites was studied in the rat spinal dorsal horn using 125I-labelled Bolton-Hunter-SP. Three months after local application of capsaicin onto the sciatic nerve quantitative evaluation of the autoradiograms revealed a significant decrease in the density of SP binding sites of up to 48% in regions of laminae I and II of the spinal dorsal horn somatotopically related to the capsaicin treated sciatic nerve. It is suggested that reduction in SP binding may result from transganglionic and transsynaptic degenerative changes affecting postsynaptic structures. Changes in the distribution of SP binding sites may significantly contribute to functional alterations observed after perineural treatment with capsaicin.

Afferent Pathways↗
PubMed1995

RT97: a marker for capsaicin-insensitive sensory endings in the rat skin.

The mouse monoclonal antibody RT97, which recognises the 200-kDa neurofilament subunit in its phosphorylated form, selectively labels the somata of sensory A-fibres (large light cells) in the dorsal root ganglion of the rat. We have tested the hypothesis that this antibody also visualises large diameter sensory fibres and their end structures in peripheral tissue, in particular in the skin. RT97 immunoreactivity is found in endings that are known to be served by myelinated afferent fibres, including Meissner-like endings, Merkel discs, hair follicle receptors, Pacinian corpuscles and free nerve endings. RT97 immunoreactivity has not, however, been observed in endings of presumably unmyelinated sensory fibres (intraepidermal fibres immunoreactive for substance P and calcitonin gene-related peptide) or in sympathetic fibres innervating sweat glands and blood vessels. In addition, neither systemic (100-150 mg/kg as adults) nor perineural capsaicin pre-treatment affects RT97 immunoreactivity in the skin. The data indicate that RT97 is a useful marker in the study of the capsaicin-insensitive sensory innervation of the skin and possibly other peripheral organs.

Animals↗
PubMed1995

Capsaicin treatment induces selective sensory degeneration and increased sympathetic innervation in the rat ureter.

Quantitative immunohistochemistry was used to study the innervation of the ureter in adult rats pretreated with capsaicin as neonates (50 mg/kg) or as adults (100-150 mg/kg, 10-22 days prior to being killed) using antibodies against protein gene-product 9.5, neuron-specific enolase, substance P, calcitonin gene-related peptide, neuropeptide Y, dopamine-beta-hydroxylase and vasoactive intestinal polypeptide. The number of calcitonin gene-related peptide- and substance P-containing fibres was reduced in the subepithelial plexus (adult capsaicin treatment < 1%, neonatal treatment < 5% of control), the submucosa (adult treatment < 11%; neonatal treatment < 51%) and in the smooth muscle layer and adventitia (adult treatment < 11%; neonatal treatment < 58%). Fibres immunoreactive for protein gene-product 9.5, a general neuronal marker, were reduced to 11% (adult treatment) or 0.5% (neonatal treatment) in the subepithelial plexus, but unchanged in the other layers, indicating a selective regional degeneration. In the smooth muscle layer the number of neuropeptide Y- and vasoactive intestinal polypeptide-containing nerve fibres was not altered by capsaicin. The number of neuropeptide Y fibres in the subepithelial plexus, however, was significantly increased after adult treatment (174% of control). After neonatal capsaicin treatment the intensity of the neuropeptide Y immunoreactivity was increased, more neuropeptide Y-positive nerve bundles were found and immunoreactive cell bodies were observed regularly in the adventitia of the ureter. The data indicate that capsaicin produces a selective degeneration of most afferent fibres in the subepithelial plexus of the rat ureter. This loss of capsaicin-sensitive afferent nerves evokes neuroplastic changes resulting in a hyperinnervation by neuropeptide Y-immunoreactive, presumably sympathetic fibres. The results suggest a mutual regulation of the pattern and density of innervation of peripheral target tissues by sensory and sympathetic neurons.

Animals↗
PubMed1993

Functional properties of mechanosensitive units from the chicken ureter in vitro.

A total of 66 mechanosensitive units was recorded from an in vitro preparation of the chicken ureter with attached nerves. They were classified into three groups according to their functional properties. U-1 units (30% of the units) responded to contractions of the ureter and exhibited very low spontaneous activity (mean: 0.1 Hz). They had low average thresholds to distension (5.8 mmHg or 0.77 kPa), responded immediately to mechanical stimuli without exhibiting after discharges to strong stimuli. Their function might be the monitoring of peristalsis. U-2 units (38%) did not respond to contractions and had irregular spontaneous activities (mean: 0.7 Hz). They exhibited a high average activation threshold to distension (42.6 mmHg or 5.73 kPa) and after discharges to strong mechanical stimuli. U-2 units might be involved in nociception. U-G units (32%) were characterized by their long-latency response to any mechanical stimulus used and had a regular high ongoing activity (mean: 2.2 Hz). The pressure thresholds cover the whole range of the U-1 and U-2 units (5 to 70 mmHg or 0.67-9.33 kPa) with an average of 31.5 mmHg or 4.2 kPa. The peak discharge to pressure stimuli occurred much later than in the U-1 and U-2 units and they exhibited pronounced after discharges. Some U-G units were inhibited by mechanical stimuli. U-G units had large receptive fields sometimes covering the entire ureter. The units responded to electrical stimulation of the ureter after a variable latency, indicating that they were synaptically driven. In addition, a late long-lasting response to electrical stimulation was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Mustard oil-induced cutaneous inflammation in the pig.

Recent findings indicate that chemical stimulation of the porcine skin with capsaicin evokes a flare response similar to that observed in man. The aim of the present study was to elucidate whether chemical stimulation of cutaneous capsaicin-sensitive nerve endings with mustard oil produces neurogenic inflammatory reactions in the pig. The application of mustard oil onto the abdominal skin of domestic pigs resulted in a pronounced flare response. After a previous intravenous injection of a solution of Evans blue, the skin area in contact with the irritant turned dark blue, indicating a marked extravasation of albumin. Quantitative estimation of the dye content of the skin supported this conclusion. The technique of vascular labelling revealed a delicate network of small subepidermal blood vessels in histological preparations after the application of mustard oil following a previous intravenous injection of colloidal silver. Labelled blood vessels were not noted outside the treated area. The present results show that mustard oil produces a strong cutaneous inflammatory response in the pig, and suggest that the porcine skin provides a valuable model for study of the significance of capsaicin-sensitive sensory nerves in vascular and other cutaneous reactions.

Animals↗
PubMed1993

Distribution and binding sites of substance P and calcitonin gene-related peptide and their capsaicin-sensitivity in the spinal cord of rats and chicken: a comparative study.

In a comparative study, the distribution and binding sites of substance P (SP) and calcitonin gene-related peptide (CGRP) in the spinal cord, and their susceptibility towards capsaicin pretreatment were studied in rats and chicken. Rats: In accordance with the SP immunohistochemistry, specific binding sites for 125I-Bolton-Hunter-SP were highest in laminae I-III. Binding sites for 125I-0Tyr-rat-CGRP were found to be dense around the central canal, moderate in the dorsal and weak in the ventral horn. Neonatal capsaicin pretreatment, that reduced SP and CGRP immunoreactivities, increased SP specific binding sites in laminae I-III and X by 20 and 100%, respectively. An increase in CGRP binding density was detected in laminae IV, V and in the lumbar ventral horn. Displacement studies revealed a significant decrease of EC50-values for SP. Chicken: SP and CGRP immunoreactivities and SP specific binding sites were distributed similarly as in rats. Binding sites for radiolabelled CGRP, however, were highest in lamina X and in the ventral horn. Capsaicin (800 mg/kg) injected into the eggs 9 days before hatching had no influence on growth rate, nociception, peptide immunoreactivities and binding of the respective radioligands. The data demonstrated a different action of capsaicin on SP and CGRP and their specific binding sites in the spinal cord of rats and chicken and were discussed with regard to functional differences between these two animal species.

Animals↗
PubMed1993

Identification of cholinergic neurons in enteric nervous system by antibodies against choline acetyltransferase.

Several different monoclonal and polyclonal antibodies to choline acetyltransferase (ChAT) were screened to identify effective antibodies for immunocytochemical marking of cholinergic neurons in the enteric nervous system. Excellent immunohistochemical results were obtained with two of the antibodies in the myenteric plexus of the guinea pig stomach and small intestine. One was a mouse monoclonal antibody designated B3.9B3, and the second was a rabbit polyclonal antibody referred to as Peptide 3. Both antibodies clearly stained neuronal cell bodies as well as nerve fibers to the muscle layers and fibers encircling stained and unstained cell bodies. Cell counts indicated that approximately 64% (21.0 +/- 8.6 cells/ganglion) of gastric myenteric neurons are ChAT positive. Pelvic ganglia and the inferior mesenteric ganglia were examined as controls. Strong labeling of the majority of neurons was found in the pelvic ganglia, whereas few immunoreactive cells were apparent in the predominantly noradrenergic inferior mesenteric ganglion. Lack of effective antibodies to enteric neuronal ChAT has hampered progress in the study of the neurophysiology of cholinergic neurons in the digestive tract. Application of the B3.9B3 and Peptide 3 antibodies now promises to facilitate investigation of this important subset of enteric neurons.

Animals↗