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P Holzer

Publications and source records attributed to P Holzer.

At least 109 records · Page 6Linked to original sources
PubMed1993

A monoclonal antibody to calcitonin gene-related peptide abolishes capsaicin-induced gastroprotection.

Calcitonin gene-related peptide (CGRP) released from vasodilator nerves is implicated in the gastroprotective action of capsaicin. This experimental paradigm was used to prove the effectiveness of a monoclonal anti-CGRP antibody. The experiments were performed in anaesthetized rats in which intragastric capsaicin (0.5 mg/kg) reduced gastric injury due to ethanol (50%) by 72%. The protective effect of capsaicin was abolished by close arterial administration of the anti-CGRP antibody #4901 (5 mg) to the stomach. A monoclonal antibody to keyhole limpet haemocyanin was without effect. These data establish anti-CGRP antibody #4901 as a tool to neutralize endogenously released CGRP and show that CGRP is indispensable for the gastroprotective action of capsaicin.

Animals↗
PubMed1993

Participation of nitric oxide in the mustard oil-induced neurogenic inflammation of the rat paw skin.

The possibility of nitric oxide (NO) participating in the neurogenic inflammatory reaction of the rat hindpaw skin to topical application of mustard oil was examined in anesthetized rats. Vasodilation was measured by contactless infrared emission thermography, plasma protein exudation was measured by the Evans blue leakage technique, and formation of oedema was determined by measurement of the paw volume. Topical administration of mustard oil increased the temperature of the paw skin by 2-3 degrees C, a response that was accompanied by plasma protein extravasation and followed by development of slight oedema amounting to a 7-8% increase in paw volume. That the mustard oil-induced increase in paw temperature and oedema formation was neurogenic was shown by the finding that both responses were absent in adult rats treated with a neurotoxic dose of capsaicin (0.16 mmol kg-1 s.c.) as neonates. NG-Nitro-L-arginine methyl ester (L-NAME, 43 mumol kg-1 i.v.) an inhibitor of NO formation, caused a significant increase in mean arterial blood pressure and a moderate decrease in cutaneous blood flow, whereas the same dose of the inactive enantiomer, D-NAME, was without effect. L-NAME, but not D-NAME, reduced the cutaneous hyperaemia caused by topical administration of mustard oil by about 50% but did not significantly diminish the exudative reaction to mustard oil. These findings indicate that endothelium-derived NO plays a mediator role in the vasodilator component of mustard oil-induced neurogenic inflammation in the rat paw skin whereas the increase in vascular permeability does not seem to involve NO directly as a mediator.

Amino Acid Oxidoreductases↗
PubMed1993

Gastric hyperemia accompanying acid secretion is not mediated by sensory nerves.

It is not known how the signal to increase gastric mucosal blood flow is passed from the gastric parietal cell layer to the resistance vessels in the submucosa. We tested the hypothesis that mucosal hyperemia accompanying stimulated gastric acid secretion is mediated by capsaicin-sensitive sensory nerves. Rats were denervated by systemic capsaicin treatment (125 mg/kg, subcutaneously, 10-14 days prior to experimentation). Acid secretion was stimulated by intravenous pentagastrin (4, 12, and 36 micrograms/kg/hr) and was measured by a continuous perfusion method. Mucosal blood flow was measured by the hydrogen gas clearance method. Sensory denervation did not affect basal blood pressure, gastric acid secretion, or mucosal blood flow. In control rats, increases in gastric mucosal blood flow and acid secretion were dose-related. With denervation, not only was there no inhibition of the blood flow response to acid secretion, but the dose-dependent rise in acid secretion was accompanied by increased mucosal blood flow that was out of proportion to the acid secretory response. The capsaicin-sensitive afferent fibers do not transmit the signal to increase gastric mucosal blood flow in response to stimulated acid secretion. It appears that sensory nerves modulate but do not mediate the mucosal hyperemic response to acid secretion.

Analysis of Variance↗
PubMed1993

Role of nitric oxide in the vasodilator but not exudative component of mustard oil-induced inflammation in rat skin.

The participation of nitric oxide (NO) in the neurogenic inflammatory reaction of the rat hindpaw skin to topical application of mustard oil was examined by the use of NG-nitro-L-arginine methyl ester (L-NAME, 43 mumol kg-1 i.v.), an inhibitor of NO formation. Control rats received the same dose of the inactive enantiomer D-NAME. Vasodilatation was recorded by contactless infrared emission thermography, and plasma protein exudation was measured by the Evans Blue leakage technique and by measurement of the paw volume in anaesthetized rats. L-NAME reduced the cutaneous hyperaemia caused by topical administration of mustard oil by about 50% but did not change the exudative reaction to mustard oil. These findings indicate that NO plays a mediator role in the vasodilator component of neurogenic inflammation in the rat paw skin, whereas the increase in vascular permeability does not appear to depend on NO.

Administration, Topical↗
PubMed1993

Monoclonal antibody to rat alpha-CGRP: production, characterization, and in vivo immunoneutralization activity.

Spleen cells from a Robertsonian mouse immunized with rat alpha-CGRP were fused with FOX-NY cells to induce hybridoma cells. Antibody activities were screened by radioimmunoassay, and hybridomas producing high affinity antibodies were cloned by limiting dilutions. Ascites were produced from the highest affinity clone in pristine-primed Balb/c mice. Ascites fluid contained approximately 20 mg/ml IgG which was of subclass IgG2a as determined by immunodiffusion analysis. The titer of this IgG2a antibody titled #4901, was 1:2,000,000 and the ID50 for rat alpha-CGRP, rat beta-CGRP and human alpha-CGRP were 350, 4000, and 4500 pg/ml respectively. Protein A purified CGRP antibody #4901 (5-10 mg/kg) completely abolished the portal release of somatostatin and the inhibition of gastric acid secretion induced by intravenous infusion of rat alpha CGRP (15-20 micrograms/kg/h) in anesthetized rats. The unpurified antibody (25 mg/kg) also prevented the fall in mean arterial blood pressure and the increase in heart rate caused by intravenous injection of rat alpha-CGRP. Immunohistochemistry showed that CGRP monoclonal antibody stains nerve fibers and endocrine-like cells in the pancreas, and neuronal elements in the gastrointestinal tract. These results show that CGRP monoclonal antibody #4901, which is relatively specific for rat alpha-CGRP, is useful for in vivo immunoneutralization of CGRP and is also an excellent reagent for immunohistochemical localization of alpha- and beta-CGRP in mammals.

Amino Acid Sequence↗
PubMed1993

Nitric oxide-dependent and -independent hyperaemia due to calcitonin gene-related peptide in the rat stomach.

1. Calcitonin gene-related peptide (CGRP) potently enhances mucosal blood flow in the rat stomach. The aim of this study was to examine whether CGRP also dilates extramural arteries supplying the stomach and whether the vasodilator action of CGRP involves nitric oxide (NO). 2. Rat CGRP-alpha (0.03-1 nmol kg-1, i.v.) produced a dose-dependent increase in blood flow through the left gastric artery (LGA) as determined by an ultrasonic transit time technique in urethane-anaesthetized rats. Blockade of NO synthesis by NG-nitro-L-arginine methyl ester (L-NAME, 20 and 60 mumol kg-1, i.v.) significantly reduced basal blood flow (BF) in the LGA and attenuated the hyperaemic activity of CGRP by a factor of 2.8-4. D-NAME tended to enhance basal BF in the LGA but had no influence on the dilator activity of CGRP. The ability of vasoactive intestinal polypeptide to increase left gastric arterial blood flow remained unaltered by L-NAME. 3. L-NAME (20 and 60 mumol kg-1, i.v.) evoked a prompt and sustained rise of mean arterial blood pressure (MAP) and caused a slight decrease in the hypotensive activity of CGRP. In contrast, D-NAME induced a delayed and moderate increase in MAP and did not influence the hypotensive activity of CGRP. 4. Rat CGRP-alpha dilated the isolated perfused bed of the rat LGA precontracted with methoxamine and was 3 times more potent in this respect than rat CGRP-beta. The dilator action of rat CGRP-alpha in this preparation was not affected by L-NAME or D-NAME (40 microM). 5. L-NAME (60 micromol kg-1, i.v.) reduced gastric mucosal blood flow as assessed by laser Doppler flowmetry and diminished the hyperaemic activity of rat CGRP-alpha in the gastric mucosa by a factor of 4.5, whereas D-NAME was without effect.6. These data show that CGRP is a potent dilator of mucosal and extramural resistance vessels in the rat stomach. Its dilator action involves both NO-dependent and NO-independent mechanisms.

Anesthesia↗
PubMed1993

Chronic nicotine intake causes vascular dysregulation in the rat gastric mucosa.

Chronic cigarette smoking has adverse effects on peptic ulcer disease because the healing of ulcers is delayed and the incidence of relapses is enhanced. Short term intake of nicotine induces vascular damage in the rat gastric mucosa, but the pathophysiological mechanisms of nicotine's action in the stomach are largely unknown. In this study rats were treated with nicotine, added to their drinking water, for 50 days. They were then anaesthetised and their stomachs perfused with acidified acetylsalicylic acid (ASA). Chronic nicotine treatment failed to change the effects of acidified ASA to induce gastric mucosal acid back diffusion, haemorrhagic damage and bleeding. Basal blood flow in the gastric mucosa was also unchanged by chronic nicotine intake, whereas the mucosal hyperaemia evoked by ASA induced acid back diffusion was averted. The concentrations of sulfidoleukotrienes were significantly augmented in the gastric wall of nicotine treated rats. These data show that chronic nicotine intake causes dysregulation of the gastric microcirculation, an effect that is associated with biochemical changes in the stomach. This study thus substantiates the adverse effects of smoking on gastric mucosal pathophysiology. These data suggest that inappropriate regulation of gastric mucosal blood flow inhibits recovery from gastric mucosal injury in smokers.

Animals↗
PubMed1993

Ablation of capsaicin sensitive afferent nerves impairs defence but not rapid repair of rat gastric mucosa.

Capsaicin sensitive afferent neurones have previously been reported to play a part in gastric mucosal protection. The aim of this study was to investigate whether these nociceptive neurones strengthen mucosal defence against injury or promote rapid repair of the damaged mucosa, or both. This hypothesis was examined in anaesthetised rats whose stomachs were perfused with ethanol (25 or 50% in saline, wt/wt) for 30 minutes. The gastric mucosa was inspected 0 and 180 minutes after ethanol had been given at the macroscopic, light, and scanning electron microscopic level. Rapid repair of the ethanol injured gastric mucosa (reduction of deep injury, partial re-epithelialisation of the denuded surface) took place in rats anaesthetised with phenobarbital, but not in those anaesthetised with urethane. Afferent nerve ablation as a result of treating rats with a neurotoxic dose of capsaicin before the experiment significantly aggravated ethanol induced damage as shown by an increase in the area and depth of mucosal erosions. Rapid repair of the injured mucosa, however, as seen in rats anesthetised with phenobarbital 180 minutes after ethanol was given, was similar in capsaicin and vehicle pretreated animals. Ablation of capsaicin sensitive afferent neurones was verified by a depletion of calcitonin gene related peptide from the gastric corpus wall. These findings indicate that nociceptive neurones control mechanisms of defence against acute injury but are not required for rapid repair of injured mucosa.

Animals↗
PubMed1993

Inhibitory role of capsaicin-sensitive afferent neurons and nitric oxide in hemostasis.

Capsaicin-sensitive afferent neurons control blood flow via release of peptide transmitters and formation of nitric oxide (NO). The present study examined whether capsaicin-sensitive afferent neurons and NO interact in the control of hemostasis. Afferent nerve ablation by pretreating rats with a neurotoxic dose of capsaicin (125 mg/kg) led to a 26% reduction of the time of bleeding from punctured small mesenteric arteries in pentobarbital-anesthetized animals. Blockade of NO formation by NG-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg) attenuated the bleeding time in capsaicin-pretreated rats but had no effect in vehicle-pretreated rats. Platelet aggregation induced by ADP was significantly augmented by 12% in capsaicin-pretreated rats. L-NAME did not alter platelet aggregation in vehicle-pretreated rats but enhanced it in capsaicin-pretreated animals. The prothrombin and partial thromboplastin time and the plasma levels of fibrinogen and antithrombin III remained unchanged by capsaicin or L-NAME, whereas the thrombin time was reduced in capsaicin-pretreated rats. These data indicate that capsaicin-sensitive afferent neurons play an inhibitory role in platelet aggregation and hemostasis, a function in which they interact with the NO system.

Animals↗
PubMed1993

Ascending enteric reflex contraction: roles of acetylcholine and tachykinins in relation to distension and propagation of excitation.

The ascending reflex contraction of intestinal circular muscle involves both cholinergic and tachykininergic transmission, which are thought to be activated by different degrees of distension. Substance P, however, is colocalized with acetylcholine in myenteric neurons, and the present study examined the role of these transmitter substances in relation to low- and high-degree distension and with regard to ascending propagation of excitation. Reflex contractions in segments of the guinea pig isolated small intestine were evoked by inflation of an intraluminal balloon and recorded orally to the site of distension. Atropine (12.5 nM), hexamethonium (3 microM) and the neurokinin (NK)2-selective tachykinin antagonist MEN 10,376 (10 microM) inhibited contractions induced by low-degree distension to a larger extent than contractions induced by high-degree distension, whereas the receptor-nonselective tachykinin antagonist spantide (30 microM) did not differentiate in this way. Atropine, hexamethonium and spantide also depressed the propagation of excitation, i.e., the response recorded 2 cm away from the distension site was inhibited to a larger degree than the response recorded 1 cm away from the distension site. In contrast, MEN 10,376 did not interfere with the ascending propagation of excitation, and the NK1-selective tachykinin antagonist GR 82,334 (10 microM) was without effect on the ascending reflex contraction. These observations show that tachykinins and acetylcholine comediate ascending reflex contractions triggered by both low- and high-degree distension. When seen in context with the known projection of myenteric neurons, the findings relating to the ascending propagation of excitation indicate that NK2 receptors participate in neuromuscular transmission only, whereas neuroneuronal transmission involves both nicotinic and muscarinic acetylcholine receptors.

Acetylcholine↗
PubMed1992

Participation of capsaicin-sensitive afferent neurons in gastric motor inhibition caused by laparotomy and intraperitoneal acid.

Stimulation of somatic or visceral nociceptors causes changes in gastrointestinal motor activity and blood pressure. The present study examined the possible participation of capsaicin-sensitive afferent and noradrenergic efferent neurons in the blood pressure and gastric motor responses to laparotomy and intraperitoneal injection of capsaicin or hydrochloric acid in the rat. Gastric motor activity was measured by recording the intragastric pressure of phenobarbital-anaesthetized rats via an oesophageal catheter. Laparotomy as well as intraperitoneal injection of capsaicin (33 and 330 microM) or hydrochloric acid (30 mM) caused a transient reduction of gastric motor activity stimulated by intravenous infusion of bombesin (200 pmol/min) and a brief fall of blood pressure (depressor effect). The depressor effect of laparotomy was followed by prolonged hypertension. Defunctionalization of capsaicin-sensitive afferent neurons by systemic pretreatment of rats with capsaicin (0.4 mmol/kg) prevented the depressor effect and gastric motor inhibition elicited by laparotomy, intraperitoneal capsaicin (33 microM) or intraperitoneal hydrochloric acid (30 mM). However, the effects of 330 microM capsaicin on blood pressure and gastric motility were only partially reduced by capsaicin pretreatment. Blockade of noradrenergic sympathetic neurons by pretreating rats with guanethidine (0.225 mmol/kg) prevented the gastric motor inhibition and depressor effects of laparotomy and intraperitoneal injection of hydrochloric acid (30 mM). The inhibition of gastric motility caused by capsaicin (33 and 330 microM) was only partially reduced by guanethidine pretreatment. The secondary hypertension following the depressor effect of intraperitoneal capsaicin or hydrochloric acid was enhanced in guanethidine-pretreated rats whereas the prolonged hypertension induced by laparotomy was left unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Participation of endothelium-derived nitric oxide but not prostacyclin in the gastric mucosal hyperaemia due to acid back-diffusion.

1. The possible participation of prostacyclin and nitric oxide (NO) in the gastric mucosal hyperaemic response to acid back-diffusion through a disrupted gastric mucosal barrier was examined. The experiments were carried out on anaesthetized rats in which acid back-diffusion was elicited by gastric perfusion with dilute ethanol in 0.15 M HCl and gastric mucosal blood flow (MBF) was measured by the hydrogen gas clearance technique. 2. Indomethacin (28 mumols kg-1, s.c.), an inhibitor of the formation of cyclo-oxygenase products including prostacyclin, failed to alter mean arterial blood pressure (MAP), basal MBF and the hyperaemic response to acid back-diffusion in urethane-anaesthetized rats. 3. NG-nitro-L-arginine methyl ester (L-NAME; 13 and 43 mumols kg-1, i.v.), an inhibitor of endothelium-derived NO formation, increased MAP in a dose-dependent manner. Whilst basal MBF in urethane-anaesthetized rats was not changed, the increase in MBF caused by gastric perfusion with dilute ethanol in acid was dose-dependently depressed by L-NAME. The loss of H+ ions from the gastric lumen, an indirect measure of acid back-diffusion, was significantly enhanced by 43 mumols kg-1 L-NAME. In contrast, D-NAME (13 and 43 mumols kg-1) was without effect on MAP, basal and stimulated MBF, and acid back-diffusion. 4. Unlike in urethane-anaesthetized rats, L-NAME led to a significant reduction of basal MBF in phenobarbitone-anaesthetized rats. MAP in the phenobarbitone-anaesthetized rats was significantly higher than in urethane-anaesthetized rats, and the hypertensive effect of L-NAME under phenobarbitone anaesthesia was significantly smaller than under urethane anaesthesia.5. The rise in MBF brought about by acid back-diffusion was blocked by L-NAME administered to phenobarbitone-anaesthetized rats. Infusion of L-arginine (120 pmol kg -1 min- ', i.v.) led to a partial, but significant, reversal of the effects of L-NAME on MAP and the hyperaemia due to acid back-diffusion.6. These findings indicate that endothelium-derived NO plays an important mediator role in the gastric mucosal vasodilatation caused by back-diffusion whilst vasodilator prostanoids such as prostacyclin are not involved.

Anesthesia↗
PubMed1992

Gastric mucosal hyperemia due to acid backdiffusion depends on splanchnic nerve activity.

Acid backdiffusion through a disrupted gastric mucosal barrier leads to an increase in gastric mucosal blood flow (MBF). This response involves afferent neurons that pass through the celiac ganglion. The present study examined the neural pathways that underlie the rise in MBF caused by gastric perfusion with 15% ethanol in 0.15 N HCl. MBF was measured by the hydrogen gas clearance technique in urethan-anesthetized rats. Mucosal hyperemia due to acid backdiffusion was not changed by acute bilateral subdiaphragmatic vagotomy but was blocked by acute removal of the celiac-superior mesenteric ganglion complex or acute bilateral transection of the greater splanchnic nerves. Hexamethonium (85 mumol/kg iv) also attenuated the rise in MBF due to acid backdiffusion, whereas guanethidine (0.225 mmol/kg sc) had no effect. None of the procedures and drug treatments altered basal MBF to a significant extent. Transection of the splanchnic nerves, hexamethonium, and guanethidine lowered mean arterial blood pressure, but hypotension as such did not significantly influence the hyperemic response under study. Taken together, the previous and present data indicate that the rise in MBF caused by acid backdiffusion depends on the integrity of afferent and efferent neural pathways that run in the splanchnic nerves and through the celiac ganglion. The efferent pathway involves ganglionic transmission through nicotinic acetylcholine receptors but is independent of noradrenergic neurons.

Animals↗
PubMed1991

Antagonism of the effects of calcitonin gene-related peptide and of capsaicin on the guinea-pig isolated ileum by human alpha-calcitonin gene-related peptide(8-37).

The possible mediating role of calcitonin gene-related peptide (CGRP) in the effects of capsaicin in the guinea-pig ileum has been investigated by means of the CGRP antagonist hCGRP(8-37). Submaximal longitudinal muscle relaxation of the histamine-precontracted ileum evoked by rat CGRP (3 nM) or capsaicin (1 microM) was reversed by hCGRP(8-37) (1.5 microM), while that due to adrenaline or neurotensin was not affected. Inhibition of spontaneous circular muscle movements by capsaicin (100 nM) was also reversed by hCGRP(8-37). The CGRP antagonist had no effect on electrical stimulation-evoked ileal contractions or on the longitudinal or circular muscle tone. It is concluded that (a) hCGRP(8-37) is a specific CGRP antagonist in the ileum, apparently devoid of intrinsic activity or any effect not related to CGRP; (b) the inhibitory actions of capsaicin on the longitudinal and circular muscles of the ileum are mediated, at least in part, by CGRP.

Animals↗