The Protection by Vitamin E Against Tramadol-Induced Proconvulsant Effects and Brain Damage in Pentylenetetrazole-Induced Status Epilepticus in Rats

We investigated the effect of the opioid analgesic tramadol on the development of epileptic seizures and neuronal injury and the possible modulatory effect of vitamin E (Vit E) in rats with pentylenetetrazole (PTZ)-induced status epilepticus. Rats received repeated intraperitoneal (i.p.) injections of PTZ till the development of status epilepticus and were pretreated once with tramadol (30, 60 or 90 mg/kg), vitamin E (Vit E, 70 mg/kg) or both tramadol (90 mg/kg) and Vit E (70 mg/kg) prior to starting PTZ injections. Seizure scores, the latency time and the PTZ dose for each group required to reach status epilepticus were determined and histopathological examination of the brain tissue was done. Results indicated that tramadol produced both anticonvulsant and proconvulsant effects. The anticonvulsant effects of tramadol were observed for facial twitching (stage 1), convulsive body waves (stage 2), and myoclonic jerks and rearing (stage 3) and turn over onto one side position (stage 4) that were significantly inhibited by tramadol. In contrast, tonic-clonic convulsions (stage 5) were significantly increased by 60 or 90 mg/kg of tramadol as compared to PTZ control group. The mean latency and PTZ threshold dose for status epilepticus were markedly decreased after tramadol. The administration of Vit E exerted beneficial effects in decreasing epilepsy scores and increasing both the latency time and threshold dose of PTZ for reaching status epilepticus. Meanwhile, rats treated with both tramadol and Vit E exhibited significant increase in tonic-clonic convulsions and markedly shortened latency time to reach status epilepticus compared to those treated with only Vit E. In cerebral cortex and hippocampus, PTZ resulted in apoptotic cells, darkly stained degenerated and vacuolated neurons and gliosis. These pathological changes increased after tramadol but were markedly reduced by Vit E treatment. Collectively, these results suggest that: (i) tramadol exerts both anticonvulsant and proconvulsant effects; (ii) tramadol shortened the latency time and decreased the threshold dose of PTZ for evoking status epilepticus; (iii) PTZ-induced seizures and brain damage can be inhibited by Vit E; (iv) tramadol at high doses interferes with the effect of Vit E in inhibiting tonic-clonic convulsions and in reducing brain damage.

Protective effect of hot peppers against amyloid β peptide and brain injury in AlCl3-induced Alzheimer's disease in rats

Objectives

This study investigated the therapeutic effect of red hot pepper (Capsicum annuum) methanolic extract in induced Alzheimer's disease using AlCl₃ in male rats.

Materials and Methods

Rats were injected with AlCl₃ intraperitoneally (IP) daily for two months. Starting from the 2nd month of AlCl₃, rats received, in addition, IP treatments with Capsicum extract (25 and 50 mg/kg) or saline. Other groups received only saline or Capsicum extract at 50 mg/kg for two months. Brain levels of reduced glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA) were determined. Additionally, paraoxonase-1 (PON-1) activity, interleukin-6 (IL-6), Aβ-peptide, and acetylcholinesterase (AChE) concentrations in the brain were measured. Behavioral testing included wire-hanging tests for neuromuscular strength and memory tests such as Y-maze and Morris water maze. Histopathology of the brain was also done.

Results

Compared with saline-treated rats, AlCl₃ caused significant elevation of brain oxidative stress as GSH level and PON-1 activity were depleted along with MDA and NO level elevation in the brain. There were also significant increases in brain Aβ-peptide, IL-6, and AChE levels. Behavioral testing indicated that AlCl₃ decreased neuromuscular strength and impaired memory performance. Capsicum extract given to AlCl₃-treated rats significantly alleviated oxidative stress and decreased Aβ-peptide and IL-6 in the brain. It also improved grip strength and memory functioning and prevented neuronal degeneration in the cerebral cortex, hippocampus, and substantia nigra of AlCl₃-treated rats.

Conclusion

Short-term administration of ASA (50 mg/kg) has adverse effects on male reproductive function in mice. Co-administration of melatonin protects against ASA-induced impairment of male reproductive function by preventing the reduction in serum TAC and testosterone levels seen with ASA treatment alone.

The effect of low dose amphetamine in rotenone-induced toxicity in a mice model of Parkinson's disease

OBJECTIVES

The effects of low dose amphetamine on oxidative stress and rotenone-induced neurotoxicity and liver injury were examined in vivo in a mice model of Parkinson's disease.

MATERIALS AND METHODS

Male mice were treated with rotenone (1.5 mg/kg, every other day for two weeks, subcutaneously). Mice received either the vehicle or amphetamine intraperitoneally at doses of 0.5, 1.0, or 2.0 mg/kg. Oxidative stress was assessed by measurement of the lipid peroxidation product malondialdehyde (MDA), nitric oxide (NO), total anti-oxidant capacity (TAC), and paraoxonase-1 (PON-1) activity in the brain and liver. In addition, brain concentrations of nuclear factor kappa B (NF-κB) and tyrosine hydroxylase were determined and histopathology and Bax/Bcl-2 immunohistochemistry were performed.

RESULTS

The levels of lipid peroxidation and NO were increased and TAC and PON-1 were decreased significantly compared with vehicle-injected control mice. There were also significantly increased NF-κB and decreased tyrosine hydroxylase in the brain following rotenone administration. These changes were significantly attenuated by amphetamine. Rotenone caused neurodegenerative changes in the substantia nigra, cerebral cortex, and hippocampus. The liver showed degenerative changes in hepatocytes and infiltration of Kupffer cells. Bax/Bcl2 ratio was significantly increased in brain and liver tissues. Amphetamine prevented these histopathological changes and the increase in apoptosis evoked by rotenone.

CONCLUSION

These results suggest that low dose amphetamine exerts anti-oxidant and anti-apoptotic effects, protects against rotenone-induced neurodegeneration, and could prevent neuronal cell degeneration in Parkinson's disease.

Cannabis sativa Increases Seizure Severity and Brain Lipid Peroxidation in Pentylenetetrazole-Induced Kindling in Rats

The effect of Cannabis sativa extract on chemical kindling induced in rats by the repeated intraperitoneal (ip) injections of pentylenetetrazole (PTZ) was studied. Rats were treated with PTZ (35 mg/kg) once every 48 hours for 12 times alone or with ip Cannabis sativa (20 mg/kg expressed as Δ9-THC content) 30 min prior to PTZ injection. Seizures were recorded for 20 minutes. Control rats received ip saline. Cannabis treatment caused significant elevation of mean seizure score as compared to PTZ only group after the 5th, 6th and 7th PTZ repeated injections during seizure development. In particular, cannabis caused significant elevation in the frequency of myoclonic jerks, rearing (stage 3), turn over onto one side position and back position (stage 4), and generalized tonic-clonic seizures (stage 5) compared with the PTZ only group. PTZ caused significant elevations in brain lipid peroxidation (malondialdehyde), and nitric oxide along with deceased reduced glutathione level. In addition, brain acetylcholinesterase (AChE) activity significantly decreased compared to control value after PTZ treatment. Cannabis given to PTZ treated rats caused significant increase in brain malondialdehyde and AChE activity compared to PTZ only group. Reduced glutathione level was restored by cannabis. Histopathological studies indicated the presence of spongiform changes, degenerated and necrotic neurons, inflammatory cells, and gliosis in cerebral cortex and degeneration of some Purkinje cells in the cerebellum in both PTZ- and cannabis-PTZ-treated groups. It is concluded that in an epilepsy model induced by repeated PTZ administration, cannabis increased lipid peroxidation and mean seizure score.

Oxidative status and the response to pegylated-interferon alpha2a plus ribavirin in chronic genotype 4 HCV hepatitis

Oxidative stress may play a pathogenic role in chronic hepatitis C (CHC). The present study examined the oxidative status in plasma of patients with CHC who received pegylated interferon and ribavirin therapy. The following groups were included: (1) sustained virological response (28 patients), (2) null response (26 patients), (3) breakthrough (24 patients), (4) relapse (24 patients), (5) spontaneous cure (23 patients) and (6) twenty five normal subjects as a control group. Markers of oxidative stress including plasma malondialdehyde, nitric oxide, reduced glutathione, total antioxidant capacity and uric acid as well as serum ALT, AST, alkaline phosphatase, total bilirubin, albumin, prothrombin time were studied. The study indicated significant decline in reduced glutathione and total antioxidant capacity and markedly elevated levels of malondialdehyde and nitric oxide in all groups compared with the controls. Null response group had the highest levels of malondialdehyde and nitric oxide. Nitric oxide was significantly higher in those with null response compared with all other groups and with control subjects. Uric acid was significantly higher in spontaneous cure group compared with all other groups and with the controls. We concluded that CHC patients had increased oxidative stress. The oxidative status in plasma of these patients was not changed by antiviral therapy. The study also showed an important contribution of nitric oxide in null response patients. High serum uric acid did not interfere with the response and/or did not predict the response to antiviral therapy.

Cannabis-induced impairment of learning and memory: effect of different nootropic drugs

Cannabis sativa preparations are the most commonly used illicit drugs worldwide. The present study aimed to investigate the effect of Cannabis sativa extract in the working memory version of the Morris water maze (MWM; Morris, 1984[43]) test and determine the effect of standard memory enhancing drugs. Cannabis sativa was given at doses of 5, 10 or 20 mg/kg (expressed as Δ(9)-tetrahydrocannabinol) alone or co-administered with donepezil (1 mg/kg), piracetam (150 mg/ kg), vinpocetine (1.5 mg/kg) or ginkgo biloba (25 mg/kg) once daily subcutaneously (s.c.) for one month. Mice were examined three times weekly for their ability to locate a submerged platform. Mice were euthanized 30 days after starting cannabis injection when biochemical assays were carried out. Malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide, glucose and brain monoamines were determined. Cannabis resulted in a significant increase in the time taken to locate the platform and enhanced the memory impairment produced by scopolamine. This effect of cannabis decreased by memory enhancing drugs with piracetam resulting in the most-shorter latency compared with the cannabis. Biochemically, cannabis altered the oxidative status of the brain with decreased MDA, increased GSH, but decreased nitric oxide and glucose. In cannabis-treated rats, the level of GSH in brain was increased after vinpocetine and donepezil and was markedly elevated after Ginkgo biloba. Piracetam restored the decrease in glucose and nitric oxide by cannabis. Cannabis caused dose-dependent increases of brain serotonin, noradrenaline and dopamine. After cannabis treatment, noradrenaline is restored to its normal value by donepezil, vinpocetine or Ginkgo biloba, but increased by piracetam. The level of dopamine was significantly reduced by piracetam, vinpocetine or Ginkgo biloba. These data indicate that cannabis administration is associated with impaired memory performance which is likely to involve decreased brain glucose availability as well as alterations in brain monoamine neurotransmitter levels. Piracetam is more effective in ameliorating the cognitive impairments than other nootropics by alleviating the alterations in glucose, nitric oxide and dopamine in brain.

Amelioration of the haloperidol-induced memory impairment and brain oxidative stress by cinnarizine

Haloperidol is a classic antipsychotic drug known for its propensity to cause extrapyramidal symptoms and impaired memory, owing to blockade of striatal dopamine D2 receptors. Cinnarizine is a calcium channel blocker with D2 receptor blocking properties which is widely used in treatment of vertiginous disorders. The present study aimed to see whether cinnarizine would worsen the effect of haloperidol on memory function and on oxidative stress in mice brain. Cinnarizine (5, 10 or 20 mg/kg), haloperidol, or haloperidol combined with cinnarizine was administered daily via the subcutaneous route and mice were examined on weekly basis for their ability to locate a submerged plate in the water maze test. Mice were euthanized 30 days after starting drug injection. Malondialdehyde (MDA), reduced glutathione (GSH) and nitric oxide (nitrite/nitrate) were determined in brain. Haloperidol substantially impaired water maze performance. The mean time taken to find the escape platform (latency) was significantly delayed by haloperidol (2 mg/kg, i.p.) on weeks 1-8 of the test, compared with saline control group. In contrast, those treated with haloperidol and cinnarizine showed significantly shorter latencies, which indicated that learning had occurred immediately. Haloperidol resulted in increased MDA in cortex, striatum, cerebellum and midbrain. GSH decreased in cortex, striatum and cerebellum and nitric oxide increased in cortex. Meanwhile, treatment with cinnarizine (20 mg/kg) and haloperidol resulted in significant decrease in MDA cortex, striatum, cerebellum and midbrain and an increase in GSH in cortex and striatum, compared with haloperidol group. These data suggest that cinnarizine improves the haloperidol induced brain oxidative stress and impairment of learning and memory in the water maze test in mice.

Neuroprotective effect of nitric oxide donor isosorbide-dinitrate against oxidative stress induced by ethidium bromide in rat brain

This study investigated the effect of systemic administration of isosorbide-dinitrate (ISDN) on oxidative stress and brain monoamines in a toxic model of brain demyelination evoked by intracerebral injection (i.c.i) of ethidium bromide (10 µl of 0.1 %). Rats received saline (control) or ISDN at 5 or 10 mg/kg for 10 days prior to injection of ethidium bromide. Rats were euthanized one day later, and then the levels of reduced glutathione (GSH), lipid peroxidation (malondialdehyde; MDA), nitric oxide (nitrite/nitrate), acetylcholinesterase (AChE) activity, paraoxonase activity as well as monoamine levels (serotonin, dopamine and noradrenaline) were assessed in the brain cortex in different treatment groups. The i.c.i of ethidium bromide resulted in increased oxidative stress in the cortex one day after its injection; (i) MDA increased by 36.9 %; (ii) GSH decreased by 20.8 %, while (iii) nitric oxide increased by 60.3 %; (iv) AChE and paraoxonase activities in cortex decreased by 35.9 % and 29.4 %, respectively; (v) serotonin was significantly increased. In ethidium bromide-treated rats, pretreatment with ISDN at 10 mg/kg decreased cortical MDA by 23.9 %. Reduced glutathione was increased by 25.1 % ISDN at 10 mg/kg, while nitric oxide showed a 32.8 and 41.7 % decrease after 5 and 10 mg/kg of ISDN, respectively. Acetylcholinesterase activity increased by 24.3 % by 10 mg/kg of ISDN. Paraoxonase activity showed further decrease by 72.2 and 83.8 % after treatment with 5 and 10 mg/kg of ISDN, respectively. The administration of ISDN decreased the level of serotonin and noradrenaline compared with the ethidium bromide only treated group. Overall, the present findings suggest neuroprotective effect of ISDN against oxidative stress in this model of chemical demyelination.

Effects of Cannabis sativa extract on haloperidol-induced catalepsy and oxidative stress in the mice

Haloperidol is a classic antipsychotic drug known for its propensity to cause extrapyramidal symptoms due to blockade of dopamine D2 receptors in the striatum. Interest in medicinal uses of cannabis is growing. Cannabis sativa has been suggested as a possible adjunctive in treatment of Parkinson's disease. The present study aimed to investigate the effect of repeated administration of an extract of Cannabis sativa on catalepsy and brain oxidative stress induced by haloperidol administration in mice. Cannabis extract was given by subcutaneous route at 5, 10 or 20 mg/kg (expressed as Δ(9)-tetrahydrocannabinol) once daily for 18 days and the effect on haloperidol (1 mg/kg, i.p.)-induced catalepsy was examined at selected time intervals using the bar test. Mice were euthanized 18 days after starting cannabis injection when biochemical assays were carried out. Malondialdehyde (MDA), reduced glutathione (GSH) and nitric oxide (the concentrations of nitrite/nitrate) were determined in brain and liver. In saline-treated mice, no catalepsy was observed at doses of cannabis up to 20 mg/kg. Mice treated with haloperidol at the dose of 1 mg/kg, exhibited significant cataleptic response. Mice treated with cannabis and haloperidol showed significant decrease in catalepsy duration, compared with the haloperidol only treated group. This decrease in catalepsy duration was evident on days 1-12 after starting cannabis injection. Later the effect of cannabis was not apparent. The administration of only cannabis (10 or 20 mg/kg) decreased brain MDA by 17.5 and 21.8 %, respectively. The level of nitric oxide decreased by 18 % after cannabis at 20 mg/kg. Glucose in brain decreased by 20.1 % after 20 mg/kg of cannabis extract. The administration of only haloperidol increased MDA (22.2 %), decreased GSH (25.7 %) and increased brain nitric oxide by 44.1 %. The administration of cannabis (10 or 20 mg/kg) to haloperidol-treated mice resulted in a significant decrease in brain MDA and nitric oxide as well as a significant increase in GSH and glucose compared with the haloperidol-control group. Cannabis had no significant effects on liver MDA, GSH, nitric oxide in saline or haloperidol-treated mice. It is concluded that cannabis improves catalepsy induced by haloperidol though the effect is not maintained on repeated cannabis administration. Cannabis alters the oxidative status of the brain in favor of reducing lipid peroxidation, but reduces brain glucose, which would impair brain energetics.

The effect of different antidepressant drugs on oxidative stress after lipopolysaccharide administration in mice

This study investigated the effect of the serotonin selective reuptake inhibitors (SSRIs) fluoxetine, sertraline, fluvoxamine and the tricyclic antidepressant (TCA) impiramine on oxidative stress in brain and liver induced by lipopolysaccharide administration in mice. Each drug was administered subcutaneously at doses of 10 or 20 mg/kg, for two days prior to intraperitoneal (i.p.) administration of lipopolysaccharide E (LPS: 200 µg/kg). Mice were euthanized 4 h after administration of the lipopolysaccharide. Lipid peroxidation (malondialdehyde; MDA), reduced glutathione (GSH) and nitric oxide (nitrite/nitrate) concentrations were measured in brain and liver. Results: The administration of lipopolysaccharide increased oxidative stress in brain and liver; it increased brain MDA by 36.1 and liver MDA by 159.8 %. GSH decreased by 34.1 % and 64.8 % and nitric oxide increased by 78.7 % and 103.8 % in brain and liver, respectively. In brain, MDA decreased after the administration of sertraline and by the lower dose of fluoxetine or fluvoxamine, but increased after the higher dose of imipramine. Reduced glutathione increased after sertraline, fluvoxamine and the lower dose of fluoxetine or imipramine. Nitric oxide decreased by sertraline, fluoxetine, fluvoxamine and by the lower dose of imipramine. In the liver, all drugs decreased MDA and increased GSH level. Nitric oxide is decreased by sertraline, fluvoxamine and by the lower dose of fluoxetine or imipramine. It is concluded that, during mild systemic inflammatory illness induced by peripheral bacterial endotoxin injection, the SSRIs fluoxetine, sertraline and fluvoxamine reduced, while the TCA impiramine increased oxidative stress induced in the brain. The SSRIs as well as imipramine reduced oxidative stress due to lipopolysaccharide in liver tissue.

The effects of trimetazidine on lipopolysaccharide-induced oxidative stress in mice

The effects of trimetazidine, a novel anti-ischemic agent, on the development of oxidative stress induced in mice with lipopolysaccharide endotoxin were investigated. The drug was administered orally once daily at doses of 1.8, 3.6 or 7.2 mg/kg for two days prior to intraperitoneal (i.p.) injection of lipopolysaccharide E (200 μg/kg) and at time of endotoxin administration. Mice were euthanized 4 h after administration of the lipopolysaccharide. Lipid peroxidation (malondialdehyde; MDA), reduced glutathione (GSH) and nitric oxide (nitrite/nitrate) concentrations were measured in brain and liver. The administration of lipopolysaccharide increased oxidative stress in both the brain and liver tissue. MDA increased by 33.9 and 107.1 %, GSH decreased by 23.9 and 84.3 % and nitric oxide increased 70.3 and 48.4 % in the brain and liver, respectively. Compared with the lipopolysaccharide control group, brain MDA decreased by 26.2 and 36.7 %, while GSH increased by 18.2 and 25.8 % after the administration of trimetazidine at 3.6 and 7.2 mg/kg, respectively. Brain nitric oxide decreased by 45.3, 50.8 and 57.0 % by trimetazidine at 1.8, 3.6 and 7.2 mg/kg, respectively. In the liver, MDA decreased by 18.7, 30.7 and 49.4 % and GSH increased by 150.3, 204.8 and 335.4 % following trimetazidine administration at 1.8, 3.6 and 7.2 mg/kg. Meanwhile, nitric oxide decreased by 17.3 % by 7.2 mg/kg of trimetazidine. These results indicate that administration of trimetazidine in the presence of mild systemic inflammatory response alleviates oxidative stress in the brain and liver.

Effect of spironolactone on pain responses in mice

The effects of spironolactone, a non-selective aldosterone antagonist, were examined on thermally-induced pain using the hot-plate and tail-flick tests, on chemogenic pain induced by intraplantar capsaicin, on electrically-induced pain, on visceral nociception induced by intraperitoneal acetic acid injection and on haloperidol-induced catalepsy in mice. Spironolactone significantly shortened response latency in the mouse tail-flick test but produced modest decreases in response latencies in the mouse hot plate test. The drug reduced the antinociceptive effect of tramadol in the hot plate test. Spironolactone in addition decreased nociceptive thresholds of electrically-induced pain in mice. In contrast, spironolactone elicited significant antinociceptive actions in the mouse acetic-acid-induced writhing assay and at doses of 20-160 mg/kg decreased capsaicin-induced chemogenic pain. Spironolactone at doses of 40 or 80 mg/kg reduced spontaneous activity and produced a significant impairment on the rotarod test in mice. The drug (10-80 mg/kg) increased the duration of catalepsy induced by haloperidol by 56.3-188.5 %. In conclusion, spironolactone increased pain behavior in a dose-dependent manner in models of thermal and electrical pain, but decreased inflammatory visceral pain due to intraperitoneal acetic acid and chemogenic pain due to intraplantar capsaicin. The effect of spironolactone on various types of pain needs further evaluation.

Study of the analgesic, anti-inflammatory, and gastric effects of gabapentin

Gabapentin, a drug used to treat neuropathic pain, was evaluated in models of acute nociceptive pain, in instances of haloperidol-induced catalepsy, carrageenan-induced paw edema, gastric lesions caused by indomethacin or ethanol, and gastric acid secretion in rats. Reaction time in a hot plate assay was delayed by gabapentin. The antinociceptive effect of the drug was produced with a dose of 12.5 mg/kg and a maximal increase in hot plate latency of 68% 1 h after drug administration was produced at 100 mg/kg. Gabapentin (25, 50 or 100 mg/kg) caused a significant rise in current threshold in a tail electrical stimulation test in mice, resulting in values of 20, 30, and 60.5% vs. control values, 1 h post-dosing. With the agent, the duration of paw licking following intraplantar capsaicin injection decreased in a dose-dependent manner. In contrast, gabapentin failed to have antinociceptive action in a mouse acetic-acidinduced writhing assay. The drug (12.5-50 mg/kg) increased the duration of catalepsy induced by haloperidol by 33.5, 47.4, and 53.2%, respectively. It had an anti-inflammatory effect at doses of 25 or 50 mg/kg. Gabapentin (12.5-50 mg/kg) reduced the number and severity of gastric mucosal lesions induced by subcutaneous indomethacin (20 mg/kg) or intragastric 96% ethanol, but at doses of 50 and 100 mg/kg it increased gastric acid secretion. In conclusion, gabapentin decreased thermal, electrical, and chemogenic pain but not visceral pain and had a gastric protective effect.

Modulation of visceral nociception, inflammation and gastric mucosal injury by cinnarizine

The effect of cinnarizine, a drug used for the treatment of vertigo was assessed in animal models of visceral nociception, inflammation and gastric mucosal injury. Cinnarizine (1.25-20 mg/kg, s.c.) caused dose-dependent inhibition of the abdominal constrictions evoked by i.p. injection of acetic acid by 38.7-99.4%. This effect of cinnarizine (2.5 mg/kg) was unaffected by co-administration of the centrally acting dopamine D2 receptor antagonists, sulpiride, haloperidol or metoclopramide, the peripherally acting D2 receptor antagonist domperidone, but increased by the D2 receptor agonist bromocryptine and by the non-selective dopamine receptor antagonist chlorpromazine. The antinociception caused by cinnarizine was naloxone insenstive, but enhanced by propranolol, atropine and by yohimbine. The antinociceptive effect of cinnarizine was prevented by co-treatment with the adenosine receptor blocker theophylline or by the ATP-sensitive potassium channel (K(ATP)) blocker glibenclamide. Cinnarizine at 2.5 mg/kg reversed the baclofen-induced antinociception. Cinnarizine at 2.5 mg/kg reduced immobility time in the Porsolt's forced-swimming test by 24%. Cinnarizine inhibited the paw oedema response to carrageenan and reduced gastric mucosal lesions caused by indomethacin in rats. It is suggested that cinnarizine exerts anti-inflammatory, antinociceptive and gastric protective properties. The mechanism by which cinnarizine modulates pain transmission is likely to involve adenosine receptors and K(ATP) channels.

Gastric mucosal integrity: gastric mucosal blood flow and microcirculation. An overview

The stomach is in a state of continuous exposure to potentially hazardous agents. Hydrochloric acid together with pepsin constitutes a major and serious threat to the gastric mucosa. Reflux of alkaline duodenal contents containing bile and pancreatic enzymes are additional important injurious factors of endogenous origin. Alcohol, cigarette smoking, drugs and particularly aspirin and aspirin-like drugs, and steroids are among exogenous mucosal irritants that can inflict mucosal injury. The ability of the stomach to defend itself against these noxious agents has been ascribed to a number of factors constituting the gastric mucosal defense. These include mucus and bicarbonate secreted by surface epithelial cells, prostaglandins, sulfhydryl compounds and gastric mucosal blood flow. The latter is considered by several researchers to be of paramount importance in maintaining gastric mucosal integrity. The aim of this paper is to review the experimental and clinical data dealing with the role of mucosal blood flow and in particular the microcirculation in both damage and protection of the gastric mucosa.

Helicobacter pylori. One bacterium and a broad spectrum of human disease! An overview

Since the historical rediscovery of gastric spiral Helicobacter pylori in the gastric mucosa of patients with chronic gastritis by Warren and Marshall in 1983, peptic ulcer disease has been largely viewed as being of infectious aetiology. Indeed, there is a strong association between the presence of H. pylori and chronic active gastritis in histology. The bacterium can be isolated in not less than 70% of gastric and in over 90% of duodenal ulcer patients. Eradication of the organism has been associated with histologic improvement of gastritis, lower relapse rate and less risk of bleeding from duodenal ulcer. The bacterium possesses several virulence factors enabling it to survive the strong acid milieu inside the stomach and possibly damaging host tissues. The sequence of events by which the bacterium might cause gastric or duodenal ulcer is still not fully elucidated and Koch's postulates have never been fulfilled. In the majority of individuals, H. pylori infection is largely or entirely asymptomatic and there is no convincing data to suggest an increase in the prevalence of peptic ulcer disease among these subjects. An increasingly growing body of literature suggests an association between colonization by H. pylori in the stomach and a risk for developing gastric mucosa-associated lymphoid tissue (MALT), MALT lymphoma, gastric adenocarcinoma and even pancreatic adenocarcinoma. The bacterium has been implicated also in a number of extra-gastrointestinal disorders such as ischaemic heart disease, ischaemic cerebrovascular disease, atherosclerosis, and skin diseases such as rosacea, but a causal role for the bacterium is missing. Eradication of H. pylori thus seems to be a beneficial impact on human health. Various drug regimens are in use to eradicate H. pylori involving the administration of three or four drugs including bismuth compounds, metronidazole, clarithromycin, tetracyclines, amoxycillin, ranitidine, omeprazole for 1-2 weeks. The financial burden, side effects and emergence of drug resistant strains due to an increase in the use in antibiotics for H. pylori eradication therapy need further reconsideration.

Small doses of capsaicin given intragastrically inhibit gastric basal acid secretion in healthy human subjects

Although the direct inhibitory effect of small dose of capsaicin on gastric secretory responses was proved in animal observations, the role of capsaicin-sensitive afferent nerves (CSAN) and the effect of capsaicin applied in small and high doses on gastric secretion in human has not been clarified yet. In this study we investigated the influence of different small doses (100-800 microg) of capsaicin given intragastrically through an orogastric tube on gastric basal secretory responses in 10 healthy human subjects. Gastric basal secretory responses (volume, H+-concentration, H+-output) were measured from the suctions of gastric juice for a 1-h period. It has been found that: a) capsaicin dose-dependently inhibited the volume and H+-output of gastric juice; b) ID50 was found to be about 400 microg for capsaicin on gastric acid secretion; c) the time interval for capsaicin-induced gastric inhibition existed for about 1 h indifferently from the higher dose (800 microg) of capsaicin given after. It has been concluded that the capsaicin (given in small doses) inhibits the gastric basal acid output via stimulation of the inhibition of capsaicin sensitive afferent nerves.

Capsaicin increases gastric emptying rate in healthy human subjects measured by 13C-labeled octanoic acid breath test

The role of capsaicin-sensitive primary afferent sensory nerves in the regulation of gastrointestinal motility in human is not clarified yet. In this study, we investigated the effect of 400 microg capsaicin given intragastrically on gastric emptying measured by 13C-octanoic acid breath test in ten healthy human subjects. Four parameters of gastric emptying curves were taken into consideration: 1) maximum value of the curve, 2) time belonging to this maximum, 3) slope of the rising part of the curve and 4) time belonging to the 50% of the area under the curve. Administration of 400 microg capsaicin significantly increased the slope of gastric emptying curve (from 0.1 +/- 0.01 to 0.139 +/- 0.014 U x min(-1), P < 0.05) and significantly decreased the time belonging to the maximum value of emptying curve (from 150 +/- 18 to 75 +/- 12 min, P < 0.05) and the time belonging to the 50% of the area under the curve (from 112 +/- 15 to 99 +/- 14 min, P < 0.05). According to our results 400 microg capsaicin enhances gastric emptying rate in healthy human subjects.

Capsaicin inhibits the pentagastrin-stimulated gastric acid secretion in anaesthetized rats with acute gastric fistula

The effect of capsaicin on basal and pentagastrin-stimulated gastric acid secretion was investigated in the urethane anaesthetized acute gastric fistula rat. Gastric acid secretion was measured by flushing of the gastric lumen with saline every 15 min or by continuous gastric perfusion. Capsaicin given into the rat stomach at 120 ng x mL(-1) prior to pentagastrin (25 microg x kg(-1), iv) reduced gastric acid secretory response to pentagastrin by 24%. Intravenous (iv) capsaicin (0.5 microg x kg(-1)) did not reduce the pentagastrin-stimulated gastric acid secretion. After topical capsaicin desensitization (3 mg x mL(-1)), basal gastric acid secretion and that in response to pentagastrin (25 microg x kg(-1), intraperitonaeally) was unaltered compared with the control group. Data indicate that topical capsaicin inhibits gastric acid secretion stimulated with pentagastrin in anaesthetized rats.

Capsaicin-sensitive afferent sensory nerves in modulating gastric mucosal defense against noxious agents

In the rat stomach, evidence has been provided that capsaicin-sensitive sensory nerves (CSSN) are involved in a local defense mechanism against gastric ulcer. In the present study capsaicin or resiniferatoxin (RTX), a more potent capsaicin analogue, was used to elucidate the role of these sensory nerves in gastric mucosal protection, mucosal permeability, gastric acid secretion and gastrointestinal blood flow in the rat. In the rat stomach and jejunum, intravenous RTX or topical capsaicin or RTX effected a pronounced and long-lasting enhancement of the microcirculation at these sites, measured by laser Doppler flowmetry technique. Introduction of capsaicin into the rat stomach in very low concentrations of ng-microg x mL(-1) range protected the gastric mucosa against damage produced by topical acidified aspirin, indomethacin, ethanol or 0.6 N HCl. Resiniferatoxin exhibited acute gastroprotective effect similar to that of capsaicin and exerted marked protective action on the exogenous HCl, or the secretagogue-induced enhancement of the indomethacin injury. The ulcer preventive effect of both agents was not prevented by atropine or cimetidine treatment. Capsaicin given into the stomach in higher desensitizing concentrations of 6.5 mM markedly enhanced the susceptibility of the gastric mucosa and invariably aggravated gastric mucosal damage evoked by later noxious challenge. Such high desensitizing concentrations of capsaicin, however, did not reduce the cytoprotective effect of prostacyclin (PGI2) or beta-carotene. Capsaicin or RTX had an additive protective effect to that of atropine or cimetidine. In rats pretreated with cysteamine to deplete tissue somatostatin, capsaicin protected against the indomethacin-induced mucosal injury. Gastric acid secretion of the pylorus-ligated rats was inhibited with capsaicin or RTX given in low non-desensitizing concentrations, with the inhibition being most marked in the first hour following pylorus-ligation. Low intragastric concentrations of RTX reduced gastric hydrogen ion back-diffusion evoked by topical acidified salicylates. It is concluded that the gastropotective effect of capsaicin-type agents involves primarily an enhancement of the microcirculation effected through local release of mediator peptides from the sensory nerve terminals. A reduction in gastric acidity may contribute to some degree in the gastric protective action of capsaicin-type agents. The vasodilator and gastroprotective effects of capsaicin-type agents do not depend on vagal efferents or sympathetic neurons, involve prostanoids, histaminergic or cholinergic pathways.

Capsaicin and the stomach. A review of experimental and clinical data

Capsaicin, the pungent principle of hot pepper, because of its ability to excite and later defunctionalize a subset of primary afferent neurons, has been extensively used as a probe to elucidate the function of these sensory neurons in a number of physiological processes. In the rat stomach, experimental data provided clear evidence that capsaicin-sensitive (CS) sensory nerves are involved in a local defense mechanism against gastric ulcer. Stimulation of CS sensory nerves with low intragastric concentrations of capsaicin protected the rat gastric mucosa against injury produced by different ulcerogenic agents. High local desensitizing concentrations of capsaicin or systemic neurotoxic doses of the agent markedly enhanced the susceptibility of the rat gastric mucosa to later noxious challenge. Resiniferatoxin, a potent analogue of capsaicin possesses an acute gastroprotective effect similar to that of capsaicin in the stomach. The gastroprotective effect of capsaicin-type agents involves an enhancement of the microcirculation effected through the release of mediator peptides from the sensory nerve terminals with calcitonin gene-related peptide being the most likely candidate implicated. They do not depend on vagal efferent or sympathetic neurons or involve prostanoids. The gastric mucosal protective effect of prostacyclin is retained after systemic or topical capsaicin desensitization. Capsaicin-sensitive fibers are involved in the repair mechanisms of the gastric mucosa. A protective role for CS sensory nerves has also been demonstrated in the colon. In most studies, capsaicin given into the stomach of rats or cats inhibited gastric acid secretion. In humans, although recent studies provide evidence in favor of a beneficial effect of capsaicin on the gastric mucosa, an exact concentration-related assessment of the effect of the agent is still lacking.

Preventive effect of atropine on indomethacin-induced gastrointestinal mucosal and vascular damage in rats

The protective effect of 'chemical vagotomy' (atropine given in three doses: 0.1, 0.5 and 1.0 mg/kg i.p.) was examined on indomethacin (IND, 20 mg/kg s.c.)-induced macroscopic gastrointestinal (GI) mucosal erosions and changes of vascular permeability in the stomach and three equal parts of small intestine and colon in rats. The different doses of atropine were administered at 0, 5, 10, 15 and 20 h after IND administration, then the number and severity of lesions were noted and the vascular damage was measured by Evans blue extravasation into the mucosa and intraluminal juice at 24 h after the IND treatment. Our results indicate that atropine ('chemical vagotomy') dose-dependently and significantly decreases the IND-induced mucosal erosions and vascular permeability in the vagal nerve-innervated parts of GI tract (i.e. the stomach, small intestine and proximal colon). Atropine in 0.5 and 1.0 mg/kg doses has a significantly higher protective effect on the vascular damage than on the macroscopic mucosal lesions in the stomach, small intestine and proximal colon. The vascular permeability is only one of those factors which have a role in the appearance of the GI mucosal erosions after IND treatment. These results suggest that the decrease of vascular permeability is involved in the protective effect of atropine against IND-induced GI mucosal damage.

Effect of resiniferatoxin on stimulated gastric acid secretory responses in the rat

The effect of the capsaicin analogue 'resiniferatoxin' (RTX) was studied on basal and stimulated gastric acid secretory responses following sc bethanechol (1.5 mg/kg), sc pentagastrin (50 micrograms/kg) and sc histamine (0.5 and 2.5 mg/kg) in the 1-h pylorus-ligated plus saline (2 ml ig)-treated rats. Resiniferatoxin applied intragastrically in doses of 0.6 and 1 microgram/kg at time of pylorus-ligation and administration of the above secretagogues reduced acid secretory responses to bethanechol by 18.3 and 26.4%, to 0.5 mg/kg histamine by 39.9 and 44.6%, to 2.5 mg/kg histamine by 21.3 and 40.8% and to pentagastrin by 10.2 and 30.9% respectively. A single sc injection of 0.4 microgram/kg of RTX abolished basal secretion in pylorus ligated rats (which did not receive ig saline). Our results indicate that locally applied RTX is capable of inhibiting basal secretory responses and modifying gastric acid responses stimulated with histamine, bethanechol or pentagastrin in the rat.