Proglumide, a cholecystokinin receptor antagonist, exacerbates beta, beta'-iminodipropionitrile-induced dyskinetic syndrome in rats

Effect of thiamazole on kainic acid-induced seizures in mice

Kainic acid (KA) induced epileptic seizures in mice is a commonly used experimental model of epilepsy. Previous studies have suggested the roles of various neurotransmitters and oxidative stress in KA-induced seizures. An important role of hypothyroidism has also been suggested in epilepsy. Thiamazole (TZ) is an anti-hyperthyroid drug with antioxidant property. This study reports the effect of TZ on KA-induced epileptic seizures in mice, produced by intraperitoneal (IP) injection of KA (18 mg/kg). Prior to KA injection, the animals were treated with TZ (12.5, 25 and 50 mg/kg IP). Our results showed that in KA alone group, about half of the animals developed seizures. Pre-treatment of mice with TZ significantly increased the frequency of seizures in dose-dependent manner. Administration of TZ significantly reduced the latency time and aggravated the severity of seizures. TZ also increased the mortality in KA-treated mice. Striatal dopamine and serotonin levels were markedly increased in KA alone treated mice, which were not significantly affected by TZ treatment. Among the indices of oxidative stress, we observed a significant reduction in cerebral vitamin E whereas the levels of cerebral malondialdehyde and conjugated dienes were significantly increased in animals with high severity of seizures. In conclusion, TZ potentiated the frequency and severity of experimental seizure in mice. There is a possibility of altered metabolism of KA in presence of TZ that might have potentiated the toxicity of KA. These findings suggest a caution while administering anti-hyperthyroid drugs in epileptic seizures.

Time-Course Evaluation of Iminodipropionitrile-Induced Liver and Kidney Toxicities in Rats: A Biochemical, Molecular and Histopathological Study

Iminodipropionitrile (IDPN) is known to produce axonopathy and vestibular hair cell degeneration. Recent histopathological studies have shown IDPN-induced liver and kidney toxicities in rodents; however, the associated mechanisms are not clearly understood. We investigated the role of proinflammatory cytokines in IDPN-induced liver and kidney toxicities in rats. Rats were treated with saline (control) and IDPN (100 mg/kg, intraperitoneally) daily for 1, 5, and 10 days, respectively. Animals were killed 24 hours after the last dose and liver and kidneys were collected for histopathology and interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α messenger RNA expression analysis. Serum aspartate aminotransferase and alanine aminotransferase activities were significantly increased after 10 doses of IDPN. The level of serum creatinine was initially increased after the first dose of IDPN but subsided on days 5 and 10. Blood urea nitrogen levels were significantly increased on days 5 and 10 following IDPN exposure. Histopathology showed dose-dependent hepatotoxicity in IDPN-treated rats. Iminodipropionitrile-induced expression of proinflammatory cytokines peaked after day 1 in liver and after day 5 in kidneys. In conclusion, repeated exposure of IDPN for 10 days produced significant structural and functional damages in rat liver whereas kidneys showed gradual recovery with time. These findings point toward the role of inflammatory mediators in IDPN-induced toxicity in rats.

Protective effects of a natural herbal compound quercetin against snake venom-induced hepatic and renal toxicities in rats

Echis pyramidum is a highly poisonous viper snake. Previous studies have shown acute phase hepatic and renal toxicities of Echis pyramidum venom (EPV) in rats. This study reports the protective effects of a natural herbal compound quercetin (QRC) on EPV-induced hepatic and renal toxicities in rats. A singly injection of EPV (4.76 mg/kg) caused significant increase in serum biomarkers of liver and kidney function. Pre-treatment of QRC (10 mg/kg) significantly reduced the toxic effects of EPV on functional impairment in liver and kidneys of rats. Administration of QRC also reversed EPV-induced increase in lipid peroxidation and decrease in total thiols. The histopathology of liver showed fat accumulation, focal degeneration and cytoplasmic vacuolation of hepatocytes in EPV treated rats. EPV also caused renal tubular dilation and focal atrophy of glomerular tufts in rat kidneys. Administration of QRC prevented EPV-induced structural tissue damage in liver and kidneys of rats. In conclusion, QRC significantly inhibited the acute phase toxic effects of EPV on liver and kidneys of rats by preventing the oxidative stress in these organs. QRC is also known for its anti-inflammatory, anti-edema, anti-hemorrhagic and PLA2-inhibitory properties and therefore may be regarded as a multi-action antidote against snake venom toxicity.

Pattern of neurobehavioral and organ-specific toxicities of β, β'-iminodipropionitrile in mice

INTRODUCTION

β, β'-iminodipropionitrile (IDPN) is a synthetic nitrile that produces a permanent movement disorder in rodents. Although IDPN-induced vestibular pathology is well documented, the mode of IDPN interaction with other organ systems is poorly understood. We examined the behavioral signs and histopathological changes in the vestibular labyrinth, brain, liver and kidneys of mice exposed to IDPN.

MATERIAL AND METHODS

Adult male SWR/J mice were divided into 2 groups of 6 animals each. One group of mice received normal saline (control group) and the other group was treated with IDPN (400 mg/kg, i.p.) daily for 7 days. Dyskinetic movements including vertical and horizontal head weaving, circling and backward walking were quantified on days 7, 8 and 9.

RESULTS

We observed a direct correlation between the severity of IDPN-induced behavioral deficits and the degeneration of vestibular hair cells in the crista ampullaris of mice. The brain cortex of both groups appeared similar, whereas the kidney histopathology revealed mild nephrotoxicity in some of the IDPN-treated mice. Administration of IDPN caused severe hepatotoxicity, but the intensity of hepatic damage was not correlated with the severity of behavioral deficits.

CONCLUSIONS

Degeneration of vestibular sensory hair cells plays an important role in the development of IDPN-induced behavioral deficits in mice. Exposure to IDPN also caused severe hepatotoxicity which was independent of the behavioral symptoms. These findings could be of potential relevance to human health, particularly after the observation that IDPN not only causes a movement disorder but also produces acute liver injury.

Effects of Echis pyramidum snake venom on hepatic and renal antioxidant enzymes and lipid peroxidation in rats

The effects of Echis pyramidum venom (EPV) (0.25, 0.50, and 1.00 mg/kg) on activities of superoxide dismutase (SOD) and catalase (CAT) and levels of thiobarbituric acid reactive substances (TBARS) and total thiols (T-SH) in liver and kidneys of rats were investigated. EPV significantly and dose dependently decreased the activities of SOD and CAT in livers. Although the kidney SOD and CAT activities were not affected by low and medium doses of EPV, the high dose significantly reduced the activities of these enzymes. Liver and kidney TBARS levels were not affected by the low and medium doses of EPV, whereas the high dose significantly increased the TBARS after 6 h postdosing. There was a significant depletion of T-SH in liver and kidneys of rats exposed to a high dose of EPV. The acute phase oxidative stress due to an EPV injection points toward the importance of an early antioxidant therapy for the management of snake bites.

Histological insights in iminodipropionitrile-induced toxicity in rats

Iminodipropionitrile (IDPN) is a prototype nitrile compound that produces excitation, chorea and circling (ECC) syndrome in rodents. Previous studies have implicated vestibular hair cell degeneration in IDPN-induced behavioral abnormalities. Although the pathological changes in vestibular labyrinth of IDPN-treated rats are well documented, the effects of IDPN on other organ systems are not clearly understood. We therefore examined the histopathological alterations in inner ear, brain, liver and kidneys of rats exposed to IDPN. Adult male Wistar rats were divided into two groups of six animals each. Control rats received normal saline whereas the IDPN group was treated with IDPN (100mg/kg, i.p.) daily for 7 days. All the animals were carefully observed for any behavioral abnormality and the dyskinetic movements including the vertical and horizontal head weaving, circling and backward walking were quantified. The animals were sacrificed on day 9 and the samples of cochlea, brain, liver and kidney were collected for histopathology. The results showed a direct correlation between the severity of behavioral deficits and the cellular damage in crista ampullaris in IDPN-treated rats. Histopathology of liver was severely influenced by IDPN treatment, leading to vacuolization of cytoplasm, distorted sinusoids, infiltration of mononuclear cells and necrotic zones. However, the severity of hepatic damage in IDPN-treated rats was independent of the magnitude of vestibular hair cell degeneration as well as the severity of behavioral deficits. Administration of IDPN in the vestibulotoxic doses did not produce any histological changes in the brain cortex and kidneys of rats.

Clinical physiology and mechanism of dizocilpine (MK-801): electron transfer, radicals, redox metabolites and bioactivity

Dizocilpine (MK-801), an extensively investigated drug possessing secondary amine and benzenoid functions, displays a wide array of biological properties, including anticonvulsant and anesthetic. There is scant discussion of biomechanism. A relevant, important finding is formation of oxidative metabolites in the hydroxylamine and phenolic categories. Analogy to cocaine metabolites suggests participation of redox entities, such as, hydroxylamine, nitroxide and nitrosonium, which can lead to electron transfer and radical formation. There is also similarity to metabolism by 3,3′-iminodipropionitrile and phencyclidine. Alternatively, the phenolic metabolites are well-known precursors of ET quinones. The review documents various physiological effects, mainly involving the central nervous system. Also of interest are the pro- and anti-oxidant properties. Considerable attention has been paid to MK-801 as an antagonist of the N-methyl-D-aspartate receptor in the glutamate category. This aspect is often associated with effects on the central nervous system. The review also provides recent literature dealing with MK-801/NMDA receptor in various areas of bioactivity. Studies were made of MK-801 involvement in working memory processing. Deficits in behavior were noted after administration of the drug. Treatment of mice with dizocilpine induced learning impairment. The influence of MK-801 on fear has been investigated. The substance is known to exert an analgesic effect in pain control. A number of reports deal with anesthetic properties.

Neurovestibular toxicities of acrylonitrile and iminodipropionitrile in rats: a comparative evaluation of putative mechanisms and target sites

This investigation was aimed to study the effects of individual and concomitant exposures of the two nitrile compounds, the industrially important acrylonitrile (ACN; 5, 15, 45 mg/kg/day) and the positive control iminodipropionitrile (IDPN; 100 mg/kg/day) in rats. The six treatment groups were 1 (control), 2 (ACN 5), 3 (ACN 15), 4 (ACN 45), 5 (IDPN), and 6 (IDPN + ACN 15). Both the drugs were started on the same day and continued for 9 days (IDPN was given daily 30 min before ACN but stopped a day earlier). The animals were daily observed for neurobehavioral abnormalities including dyskinetic head movements, circling, tail hanging, air righting reflex, and contact inhibition of righting reflex. There was no dyskinetic behavioral abnormality in the animals treated with any of the three doses of ACN whereas all the rats in IDPN alone treated group developed clear symptoms of excitation, circling, and chorea syndrome (ECC syndrome) on day 9. Concomitant treatment of rats with ACN significantly attenuated the severity of IDPN-induced behavioral deficits. Administration of ACN significantly depleted glutathione (GSH) in striatum, hippocampus and cerebral cortex; IDPN significantly reduced the GSH only in striatum. The anterior striatum showed intense tyrosine hydroxylase (TH) expression in IDPN alone treated rat as compared to control and ACN alone treated rat. Cotreatment with ACN reduced the intensity of TH immunostaining in IDPN-treated rats. Administration of IDPN alone caused massive loss of vestibular sensory hair cells in the crista ampullaris whereas the sensory epithelium appeared intact in ACN alone treated groups. The animals receiving the combination of ACN and IDPN showed comparatively less degeneration of sensory hair cells than IDPN alone group. These findings suggest that ACN and IDPN produce different behavioral effects that are exerted through entirely different mechanisms; the nervous and vestibular systems appear to be the major target sites of these toxins, respectively.

Protective effect of hydrocortisone on iminodipropionitrile-induced neurotoxicity in rats

Occupational and environmental exposure of synthetic nitriles is of potential relevance to human health. Iminodipropionitrile (IDPN), a prototype nitrile toxin, has been shown to produce dyskinetic syndrome in rodents. This study reports the effect of concomitant exposure of rats to hydrocortisone and IDPN on behavioural abnormalities namely excitation, circling and chorea (ECC) syndrome. Four groups of female Wistar rats were given hydrocortisone (0, 10, 30 and 60 mg/kg, gavage, for 10 days) 30 min. before IDPN (100 mg/kg, intraperitoneally for 8 days). Two additional groups of rats were treated with either saline (control group) or 60 mg/kg of hydrocortisone (drug alone group). The animals were observed for neurobehavioural abnormalities including dyskinetic head movement, circling, tail hanging, air righting reflex and contact inhibition of righting reflex. After behavioural studies, the animals were killed, and the discrete brain regions and temporal bones were collected for biochemistry and inner ear histopathology, respectively. Hydrocortisone significantly and dose dependently attenuated the incidence and severity of IDPN-induced behavioural syndrome. Administration of hydrocortisone (60 mg/kg) alone significantly increased glutathione (GSH) levels in olfactory bulb and striatum, whereas IDPN alone significantly reduced GSH levels in olfactory bulb, striatum and hippocampus. Hydrocortisone (60 mg/kg) significantly compensated IDPN-induced depletions of GSH in different brain regions. Hydrocortisone also protected the animals against IDPN-induced vestibular hair cell degeneration. The protective effect of hydrocortisone may be attributed to its anti-inflammatory and antioxidant properties.

Role of oxidative metabolites of cocaine in toxicity and addiction: oxidative stress and electron transfer

Cocaine is one of the principal drugs of abuse. Although impressive advances have been made, unanswered questions remain concerning mechanism of toxicity and addiction. Discussion of action mode usually centers on receptor binding and enzyme inhibition, with limited attention to events at the molecular level. This review provides extensive evidence in support of the hypothesis that oxidative metabolites play important roles comprising oxidative stress (OS), reactive oxygen species (ROS), and electron transfer (ET). The metabolites include norcocaine and norcocaine derivatives: nitroxide radical, N-hydroxy, nitrosonium, plus cocaine iminium and formaldehyde. Observed formation of ROS is rationalized by redox cycling involving several possible ET agents. Three potential ones are present in the form of oxidative metabolites, namely, nitroxide, nitrosonium, and iminium. Most attention has been devoted to the nitroxide-hydroxylamine couple which has been designated by various investigators as the principal source of ROS. The proximate ester substituent is deemed important for intramolecular stabilization of reactive intermediates. Reduction potential of nitroxide is in accord with plausibility of ET in the biological milieu. Toxicity by cocaine, with evidence for participation of OS, is demonstrated for many body components, including liver, central nervous system, cardiovascular system, reproductive system, kidney, mitochondria, urine, and immune system. Other adverse effects associated with ROS comprise teratogenesis and apoptosis. Examples of ROS generated are lipid peroxides and hydroxyl radical. Often observed were depletion of antioxidant defenses, and protection by added antioxidants, such as, thiol, salicylate, and deferoxamine. Considerable evidence supports the contention that oxidative ET metabolites of cocaine are responsible for much of the observed OS. Quite significantly, the pro-oxidant, toxic effects, including generation of superoxide and lipid peroxyl radicals, plus depletion of glutathione, elicited by nitroxide or the hydroxylamine derivative, were greater than for the parent drug. The formaldehyde metabolite also appears to play a role. Mechanistic similarity to the action of neurotoxin 3,3'-iminodipropionitrile is pointed out. A number of literature strategies for treatment of addiction are addressed. However, no effective interventions are currently available. An hypothesis for addiction is offered based on ET and ROS at low concentrations. Radicals may aid in cell signaling entailing redox processes which influence ion transport, neuromodulation, and transcription. Ideas are suggested for future work dealing with health promotion. These include use of AOs, both dietary and supplemental, trapping of the norcocaine metabolite by non-toxic complexing agents, and use of nitrones for capturing harmful radical species.

Metoclopramide attenuates iminodipropionitrile-induced oxidative stress and neurobehavioral toxicity in rats

Metoclopramide (MET) has long been used as a neuroleptic and antiemetic drug in clinical practice. Motor impairment and dyskinesia have been reported in some patients following chronic treatment with MET. Occasionally, the adverse symptoms may appear even after acute exposure to MET in more susceptible population (such as elderly individual) or due to concomitant exposure to MET and certain neurotoxins. Iminodipropionitrile (IDPN), a prototype nitrile toxin, has been shown to produce dyskinetic syndrome in rodents. This study reports the effect of concomitant exposure of rats to MET and IDPN on behavioral abnormalities in rats namely excitation, circling and chorea (ECC) syndrome. Four groups of female Wistar rats (aged 3 months) were given MET (0, 10, 40 and 80 mg/kg, i.p., for 11 days) 30 min before IDPN (100 mg/kg, i.p. for 8 days). Two additional groups of rats were treated with either saline (control group) or 80 mg/kg of MET (drug alone group). The animals were observed for neurobehavioral abnormalities including dyskinetic head movement, circling, tail hanging, air righting reflex and contact inhibition of righting reflex. Horizontal and vertical locomotor activities and fore limbs grip strength were also measured. On day 12, the animals were sacrificed and brains were collected for biochemical analysis. MET significantly and dose-dependently protected the animals against IDPN-induced ECC syndrome, motor impairment and deficiency in grip strength. MET also protected the animals against IDPN-induced oxidative stress.

Relationship between insult intensity and mode of hair cell loss in the vestibular system of rats exposed to 3,3'-iminodipropionitrile

A variety of stimuli cause sensory hair cell loss in the mammalian inner ear. This loss occurs by several differing processes, the significance of which remains undetermined. This study examines the relationship between the intensity of the damaging stimulus and the mode of hair cell loss found in the vestibular sensory epithelia of the rat. The ototoxin 3,3'-iminodipropionitrile (IDPN) was administered to rats at three different intoxication rates: acute exposure to high doses, repeated exposure to intermediate doses, and subchronic exposure to low doses. The morphology of the vestibular epithelia was examined by light microscopy and by scanning and transmission electron microscopy (SEM and TEM). In addition, DNA fragmentation in the epithelia was assessed by terminal deoxynucleotidyl transferase (tdt)-dUTP-nick-end-label (TUNEL). One day after acute IDPN, necrosis of hair cells was observed. However, at day 4 with this dose, and 1 and 4 days after repeated exposure, apoptotic figures and positive TUNEL labeling predominated. Subchronic IDPN resulted in a slowly evolving extrusion of basically intact hair cells in the crista and utricle. The data demonstrate that extrusion is a major mechanism of hair cell demise in mammals, that necrosis, apoptosis, and extrusion form a continuum of modes of hair cell loss, and that the intensity of the damaging stimulus determines the prevalence of each mode: Necrosis was most evident when the intensity was at its highest, whereas extrusion predominated when the intensity was at the lowest end of the scale.

Exacerbation of iminodipropionitrile-induced behavioral toxicity, oxidative stress, and vestibular hair cell degeneration by gentamicin in rats

This study describes the effect of gentamicin, an aminoglycoside antibiotic on iminodipropionitrile (IDPN)-induced abnormal neurobehavioral syndrome in female Sprague-Dawley rats. The animals were exposed to IDPN in the dose of 100 mg/kg/day intraperitoneally for 7 days. Gentamicin (GM) was administered intraperitoneally daily 1 h before IDPN in the doses of 10, 40, and 80 mg/kg body weight in three different groups of rats. One more group of animals received gentamicin alone (80 mg/kg) and served as the gentamicin-alone group. The intensity of IDPN induced characteristic excitation with choreiform, and the circling movement (ECC) syndrome was examined using an observational test battery including dyskinetic head movements, circling, tail hanging, air righting reflex, and contact inhibition of the righting reflex on days 6, 8, 10, 12, 19, 26, and 33. The animals for histopathological observation were sacrificed on day 10, whereas the remaining animals that were used for long-term behavioral studies were sacrificed on day 35 for biochemical observations. The blood and brain samples were collected for the analysis of blood urea nitrogen (BUN), serum creatinine, cerebral malondialdehyde (MDA), conjugated dienes, and lipid hydroperoxides, whereas temporal bones were collected for inner ear histopathology. Our results showed that gentamicin significantly and dose dependently exacerbated the incidence and the severity of the IDPN-induced behavioral syndrome. The histopathology of the inner ear demonstrated more severe loss of sensory hair cells in the crista ampullaris of the rats treated with IDPN plus gentamicin compared to the IDPN-alone treated animals. Concomitant treatment with gentamicin also potentiated IDPN-induced increase in free radical indices, suggesting a possible role of oxidative stress in gentamicin-induced aggravation of IDPN toxicity. Further studies are warranted to determine the role of aminoglycosides in nitrile toxicity and drug-induced movement disorders.

Nitric oxide synthase inhibitor aminoguanidine potentiates iminodipropionitrile-induced neurotoxicity in rats

This investigation was undertaken to study the effect of nitric oxide synthase inhibitor, aminoguanidine on iminodipropionitrile (IDPN)-induced neurobehavioral and vestibular toxicity in rats. The dyskinetic syndrome was produced in male Wistar rats by i.p. injections of IDPN (100 mg/kg) for 6 days. Aminoguanidine was administered orally in the doses of 50, 150 and 300 mg/kg, 60 min before IDPN in three different groups. Control rats received vehicle only, whereas another group was treated with 300 mg/kg of aminoguanidine alone (without IDPN). Our results showed that aminoguanidine significantly and dose dependently exacerbated the incidence and intensity of IDPN-induced dyskinetic head movements. Aminoguanidine potentiated IDPN-induced loss of air righting reflex. The histopathological examination of inner ear showed aggravation of IDPN-induced degeneration of sensory hair cells in the crista ampullaris by aminoguanidine. These results suggest the role of nitric oxide in IDPN-induced neurobehavioral and vestibular toxicity.