Effect of selenium and vitamin E on iminodipropionitrile induced dyskinesia in rats

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.

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.

Influence of age on iminodipropionitrile-induced vestibular and neurobehavioral toxicities in rats

A direct association between aging and drug-induced dyskinesia has been reported by several investigators. Iminiodipropionitrile (IDPN), a prototype nitrile compound produces a motor syndrome in rodents, which resembles neuroleptic drug induced dyskinesia. In this investigation attempt has been made to study the effect of age on IDPN induced vestibular hair cell degeneration and resulting dyskinetic syndrome. Male Wistar rats aged 3, 6 and 12 weeks received IDPN in the doses of 0, 200 and 400 mg/kg, intraperitoneally for 3 consecutive days. IDPN-induced dyskinesia was assessed using a behavioral testing battery on days 3, 4, 5, 6, 7, 14, 21 and 28. The rats were sacrificed on day 28; temporal bones were excised for vestibular histopathology and sera were collected for measuring the indices of oxidative stress (glutathione and conjugated dienes). IDPN in the dose of 200 mg/kg produced dyskinesia in 12 weeks old rats, but failed to do so in 3 and 6 weeks old rats. The high dose of IDPN (400 mg/kg) caused dyskinesia in all age groups, however, its onset and severity were age-dependent. Older rats showed an early onset and significantly high incidence of dyskinesia as compared to younger rats. The susceptibility of rats to IDPN-induced behavioral deficits was proportional to oxidative stress and degeneration of sensory hair cells in the crista ampullaris.

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.

Tolerance to beta,beta'-iminodipropionitrile (IDPN)-induced neurobehavioural and vestibular toxicity in diabetic rats

The present investigation was undertaken to study the neurotoxic effects of beta,beta'-iminodipropionitrile (IDPN) in normal, diabetic and insulin-treated diabetic rats. Sprague-Dawley male rats were divided into five groups: control, IDPN, diabetes, diabetes plus IDPN and diabetes plus insulin plus IDPN. The diabetes was induced with a single i.p. injection of streptozotocin (50 mg kg(-1)). One month after the induction of diabetes, the rats were treated with IDPN (100 mg kg(-1), i.p.) daily for 11 days. One of the diabetic groups treated with IDPN also received daily injection of insulin (25 U kg(-1), s.c.), 1 h before IDPN. The rats were observed daily for abnormal head movements and circling. The grip strength of the forelimbs was also measured. In the IDPN group the dyskinetic symptoms appeared on the 8th day, whereas the onset of dyskinesia was on the 12th day in IDPN-treated diabetic rats. The incidence and severity of dyskinesia were significantly higher in IDPN-treated normal (non-diabetic) rats as compared to IDPN-treated diabetic rats. The treatment of diabetic rats with insulin normalized striatal dopamine (DA) turnover but partially reversed diabetes-induced protection against IDPN dyskinesia. There was severe degeneration of sensory hair cells in crista ampullaris of IDPN-treated normal rats, whereas the diabetic rats showed significant protection against IDPN-induced vestibular hair cell degeneration. In conclusion, our study clearly demonstrates that diabetic rats are resistant to IDPN-induced neurobehavioural and vestibular toxicity. The results also show that diabetes-induced protection against IDPN-induced dyskinesia can be partially reversed by insulin. The mechanism behind the decreased vulnerability of diabetic animals to IDPN remains to be resolved. Further studies are warranted to investigate this paradoxical phenomenon.

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

The present investigation was undertaken to study the effect of proglumide, a cholecystokinin (CCK) receptor antagonist, on iminodipropionitrile (IDPN)-induced excitation, chorea, and circling (ECC) syndrome in rats. The animals were exposed to IDPN in the dose of 100 mg/kg/day IP for 9 days. Proglumide (PG) was administered IP daily 1 h before IDPN in the doses of 250, 500, and 750 mg/kg body weight in three different groups of rats. The animals were observed daily for neurobehavioral abnormalities including dyskinetic head movements, circling, tail hanging, air righting reflex, locomotor activity, and contact inhibition of the righting reflex. After behavioral studies, blood and brain samples were collected for the analysis of malondialdehyde (MDA), conjugated dienes, vitamin E, and glutathione peroxidase (GSH-Px). The temporal bones were also collected for inner ear histopathology. Our results showed that proglumide significantly and dose-dependently exacerbated the incidence and the severity of IDPN-induced ECC syndrome during the treatment period as well as up to 3 weeks of postdosing. Administration of IDPN produced a significant increase in MDA and conjugated dienes and a decrease in vitamin E and GSH-Px, suggesting the role of oxygen-derived free radicals (ODFR) in IDPN-induced neurotoxicity. Concomitant treatment with proglumide potentiated IDPN-induced oxidative stress. The histopathology of the inner ear showed significantly high degeneration of sensory hair cells in the crista ampullaris of the rats treated with IDPN plus proglumide compared to IDPN-alone-treated animals. Further studies are warranted to determine the role of CCK in nitrile toxicity and drug-induced dyskinesia.

Effect of vitamin E and selenium on hypothermic restraint stress and chemically-induced ulcers

The present study was undertaken to determine the effect of a combination of selenium and vitamin E on stress and chemical-induced gastric ulcers in rats. The gastric mucosal lesions were produced by hypothermic restraint stress, indomethacin, reserpine, and mucosal damaging agents including 80% ethanol, 0.6 M HCl, 25% NaCl, and 0.2 M NaOH. The gastric secretion studies were undertaken using Shay's pylorus ligation model. The results of this study demonstrated that the treatment of rats with selenium or vitamin E significantly reduced the basal gastric acid secretions when given individually; however, the combination of these agents produced a better inhibition of gastric acid secretions as compared to their individual effect. Both selenium and vitamin E were found to protect gastric mucosa against the lesions produced by hypothermic restraint stress and chemicals, but a highly significant protection was observed when they were used concomitantly. Vitamin E alone and with selenium significantly inhibited ethanol-induced depletion of gastric nonprotein sulfhydryl compounds. Our findings also showed that the combination of selenium and vitamin E provided better protection to gastric mucosa against hypothermic restraint-induced gastric wall mucus depletion. This study clearly suggests the feasibility of using selenium and vitamin E concurrently to achieve better gastroprotective effects.

Cysteamine attenuates iminodipropionitrile (IDPN) induced dyskinesia in rats

The present investigation was undertaken to study the effect of cysteamine on experimental dyskinesia in rats. The movement disorders were produced by intraperitoneal administration of iminodipropionitrile (IDPN) in the dose of 100 mg/kg per day for 11 days. Cysteamine was administered (i.p.), daily 30 minutes before IDPN in the doses of 25 mg/kg, 50 mg/kg and 100 mg/kg bodyweight in three different groups of rats. Twenty four hours after the last dose of IDPN, animals were observed for neurobehavioural changes including vertical and horizontal head weaving, circling, backwalking, grip strength and righting reflex. Immediately after behavioural studies brain specimens were collected for analysis of vitamin E and total glutathione levels. The results of behavioural studies showed that co-treatment with cysteamine protected rats against IDPN-induced dyskinesia. Our biochemical studies showed that IDPN produced a depletion of vitamin E in cerebrum, cerebellum and brain stem. Concomitant treatment with cysteamine in doses of 50 and 100 mg/kg attenuated IDPN-induced decrease in vitamin E in cerebrum and cerebellum. There was a significant decrease in cerebral glutathione in IDPN treated rats, which was attenuated by cysteamine. No significant change was observed in the glutathione levels in cerebellum and brain stem. Further studies are deemed necessary to elucidate the mode of action of cysteamine and to determine therapeutic and/or prophylactic value of this drug in the treatment of movement disorders.