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Effect of verapamil on Primphos-induced seizure in mice.

Introduction

Epilepsy is one of the major neurological diseases in humans and about one percent of the population is involved. It has been shown that epileptic seizure occurs due to occasional discharges in nerve tissue. It is recognized that occasional changes in reversible neuronal function, causing brain electrical activity. In some cases, the seizure occurs due to the entry of calcium ions into nerve cells and reducing intracellular calcium concentration in some epileptic animal models has inhibitory effect on seizures. During seizures increased intracellular calcium ion concentration and but extra cellular calcium concentration decreases [5,14]. Calcium channel antagonists for the treatment of hypertension were produced in the year 1980. Use of these drugs over time to treat other diseases was developed, such as treatment of angina, supraventricular tachycardia attack, hypertrophic cardiomyopathy, pulmonary hypertension and migraine. Recently have shown that calcium channel blockers may have anticonvulsant effects in some animal models. Calcium channel blockers inhibit calcium ion flow through L-type calcium channels sensitive to voltage [8]. It has been shown that calcium channel inhibitors in models of nerve tissue in a large protective effect [12]. Have also reported that calcium channel inhibitors on the anticonvulsant effects of some models have [1,10], but in all animal models of seizures has not demonstrated these effects [3,6]. Also in rats anticonvulsant effects of calcium channel inhibitors shown but seizure agent has not Primphos. Some medications such as anticonvulsants phenytoin and carbamazepine effect by inhibiting sodium channels directly and indirectly by preventing the flow of calcium from the membranes of neurons and reduction of excessive concentration of intracellular calcium. Specific drugs used to treat epilepsy are absence seizure kind of like channels as T-type calcium in thalamic neurons are blocked. This reduced calcium ion concentration of the important goals in development is neuroprotective and antiepileptic drugs [8,14]. Calcium entry into neurons play an important role in creating the seizures and calcium channel inhibitors have different effects on health, including cardiovascular diseases, migraine and headaches caused by vascular changes, nerve regeneration and neuronal regenerative processes [5], So it seems calcium channel inhibitors used to treat seizures can be useful. Results of these studies for the anticonvulsant effects of calcium channel inhibitors suggests, therefore likely to verapamil reduce Primphos-induced seizures. Since no research based on the combined effect of these seizures from Primphos there, in this case study seems necessary. Insecticide use in agriculture and veterinary medicine as strange since World War II and grew during the past 20 years has reached its highest rate constant. While the main consumers of agricultural insecticide industry is also large quantities of other industries use them and their applications in and around homes is considerable. Most of insecticide residues on the remaining products and people exposed to low doses of chemicals through the foods. Numerous incidents of acute insecticide poisoning caused by eating food that mainly followed during storage or transportation had been infected was created [4]. Including the insecticide, which are potential toxicity, are organophosphate. One of the organophosphate is Primphos. The aim of this study was to determine the effect of verapamil (calcium channel antagonist) on Primphos-induced seizures.

Materials and methods

Male mice NMRI, weighing between 25-30 grams, and maintenance of laboratory animals breeding center of Tabriz Islamic Azad University purchased and were kept in room temperature, light and humidity constant. Animals' access to food and water were freely. All tests were performed between 10-16 hours. Primphos and verapamil, both were solved in Twin 80 (5%). Animals were divided randomly and placed in treatment groups (each group n=10). Verapamil and Twin 80 were administered intraperitoneally with constant volume and by weight per animal. To remove the effect of injection volume on seizures, all drugs and Twin 80, at 10 ml/kg was set. First, seizures was assessed in animals receiving Primphos and then evaluated the effect of Twin 80 on Primphos-induced seizures with the above injection, 30 minutes before the seizure was determined. More experimental animals, different doses of verapamil (2.5, 5, 10, 20 and 40 mg/kg) received 30 min before the intraperitoneal injection of Primphos. To create seizures, mice received Primphos (500 mg/kg) intraperitoneally, and then the animals treated for 120 minutes were recorded by video camera. Films from the following four behaviors were recorded: starting time of clonic seizures after injection of Primphos (second), Generation time of death after Primphos injection (second), mortality after injection of Primphos (persentage) and type of seizures induced by injection of Primphos (percentage). After testing data as the mean [+ or -] SEM expression and to analyze data, ANOVA followed by Tukey multiple comparison tests were used. Value of p<0.05 to determine significance between groups was considered.

Results and discussion

Effect of Twin 80 as solvent, on Primphos-induced seizures showed that this substance has no significant effect on seizures. Therefore the results had not presented in graphs and tables have been avoided. Effect of different doses of verapamil (2.5, 5, 10, 20 and 40 mg kg) on Primphos-induced seizures showed that this drug dose-dependently reduced the Primphos-induced seizures (Graph 1 and 2) Most anticonvulsant effect of verapamil on the mortality and severity of seizures with a dose of 40 mg/kg was observed (Graph 3 and Table 1).

Discussion:

In this study, Primphos cause clonic and tonic seizures, and ultimately death. After the mice received intraperitoneal Primphos, some degree of tremor and excessive activity showed that over time the symptoms became more severe and cause death. In this study, verapamil dose dependently reduced clonic and tonic seizures and deaths from Primphos. The results showed that the results of different researchers before treatment with calcium channel antagonists, seizure activity creation of different materials down to is in agreement. If nimodipine in preventing tonic convulsions caused by PTZ [5], Aminophyline [1] and pilocarpine [10] have a protective effect, but unlike the above models in all tests anticonvulsant effect has been observed. For example Kainic acid induced seizures, administration of nimodipine before this material could not reduce seizures [12]. In another study showed that calcium channel blockers with values above 80 mg/kg could inhibit tonic seizures from chemicals including PTZ in mice and rats [3,15], but later showed that high doses of calcium channels blockers cause systemic and cardiac disorders, such as a sharp reduction in coronary blood pressure, decreased movements, imbalance, and headache relief [8,14]. Epilepsy in patients who were resistant to treatment, have reported that nimodipine in an uncontrolled study, seizure frequency is reduced [2], but in another study that two strains were unaware controls, no anticonvulsant effects was observed by nimodipine [9]. Other problems prescription drug, long-term administration of drugs with low prescribed intervals (three to four times a day to several weeks) and side effects include headache and hypotension, pronounced the man was from animal models. However, after 24 and 72 hours of administration of nimodipine, percent of alpha and theta waves was increased and vice versa percent in delta waves electroencephalogram was reduced [8,9]. Other studies have shown that the anticonvulsant effects of calcium channel blockers with other antiepileptic drugs, increases. For example, in mice and rats with concurrent administration of nimodipine with other drugs can be decreased PTZ-induced tonic seizures, seizures resulting from sound and relieve the electroshock [3,6,12]. Calcium channels blockers in experimental seizures by ischemia, bicuculine, electrical cortical shocks, nitrous oxide and alcohol withdrawal syndrome is caused due, have anticonvulsant effects [7]. In another study, calcium channel blockers such as verapamil, nifedipine and Flunarizine to prevent of penicillin-induced seizures and electroencephalogram range have changed [7]. Calcium channel inhibitors on seizures induced by N-methyl-D, L-aspartate (NMDLA) and dihydropyridine calcium channel agonist BAY K 8644 have been effective [13,14]. In another study on rats have shown that nimodipine in animal models of seizures, nerve discharge from BAY K 8644 and reduced the decrease in spike-wave EEG [14]. Also have shown that this drug is ischemic brain damage has protective effects [7]. These studies suggest that protective effects of calcium channel antagonists probably due to blocking L-type calcium channels during seizures. These drugs inhibit voltage-dependent calcium channels in seizures, the increase in intracellular calcium to prevent. Well marked that increased [Ca.sup.2+] into the cell in the incidence of certain types of seizures plays a role [5], also marked the loss of calcium outside the cell with reduced flow of calcium from the membranes of neurons for several seconds the discharge of neurons that causes seizures be prevented and the threshold increases [11]. Some of the other antiepileptic drugs such as phenytoin and carbamazepine with a direct effect on neuronal sodium channels act directly or indirectly the flow of calcium ions from the membranes of neurons are inhibited [8,14]. So it is likely that calcium channel antagonists to act with similar mechanisms. Also have shown that calcium channel blockers may inhibit calcium, sodium, chloride, potassium and calcium-dependent glutamate channels [14].

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Conclusion:

In summary, this study showed that verapamil (voltage-dependent calcium channel antagonist type L) decreased clonic and tonic seizures from Primphos in mice is probably the main mechanism anticonvulsant related to block calcium channels and reduce calcium flow within neurons. Of course, that this could be generalized to humans rather than question and anticonvulsant effects of calcium channel antagonists in humans, further investigation is needed.

Reference

[1.] Chakrabarti, A., H. Kaur Saini, S.K. Garg, 1998. Dose-finding study with nimodipine: a selective central nervous system calcium channel blockers on aminophylline induced seizure model in rats. Brian Res Bull., 45: 495-499.

[2.] De Falco, F.A., U. Bartiromo, L. Majello, Di G. Geronimo, P. Mundo, 1992. Calcium antagonist nimodipine in intractable epilepsy. Epilepsia, 33: 343-345.

[3.] Gasior, M., R. Kaminski, T. Burdniak, Z. Kleinrok, S.J. Czuczwar, 1996. Influence of nicardipine, nimodipine and flunarizine on the anticonvulsant efficacy of antiepileptics against pentylenetetrazol in mice. J Neural Transm Gen Sect., 103: 819-831.

[4.] Goodman, L.S., L.E. Limbird, J.G. Hardman, A.G. Gilman, 2001. Insecticides. In: Goodman & Gilman's the pharmacological basis of therapeutics. 10th Edition, Mc Graw-Hill, New York, USA.

[5.] Khanna, N., S. Bhalla, V. Verma, K.K. Sharma, 2000. Modulatory effects of nifedipine and nimodipine in experimental convulsions. Indian Journal of pharmacology, 32: 347-352.

[6.] Khosla, P., P. Pandhi, 2000. Anticonvulsant effect of nimodipine alone and in combination with diazepam and phenytion in a mouse model of status epilepticus. Methods Find Exp Clin Pharmacol, 22: 731-736.

[7.] Kriz, J., G. Zupan, A. Simonic, 2003. Differential effects of dihydropyridine calcium channel blockers in kainic acid-induced experimental seizures in rats. Epilepsy Research, 52: 215-225.

[8.] Kulak, W., W. Sobaniec, K. Wojtal, S.J. Czuczwar, 2004. Calcium modulation in epilepsy. Pol J Pharmacol, 56: 29-41.

[9.] Larkin, J.G., P.J. McKee, J. Blacklaw, G.G. Thompson, I.C. Morgan, M.J. Brodie, 1991 Nimodipine in refractory epilepsy: a placebo-controlled, add-on study. Epilepsy Res., 9: 71-77.

[10.] Marinho, M.M., de V.M. Bruin, de F.C. Sousa, L.M. Aguiar, de R.S. Pinho, G.S. Viana, 1997. Inhibitory action of a calcium channel blocker (nimodipine) on seizure and brain damage induced by pilocarpine and lithium-pilocarpine in rats. Neurosci Lett., 235: 13-16.

[11.] Mc Namara, J.O., 1992. The neurobiological basis of epilepsy. Trends Neurosci, 15: 357-359.

[12.] Mikati, M.A., G.L. Holmes, S. Werner, N. Bakker, L. Carmant, Z. Liu, C.E. Stafstrom, 2004. Effects of nimodipine on the behavioral sequalae of experimental status epilepticus in prepubescent rats. Epilepsy & Behavior, 5: 168-174.

[13.] Palmer, G.C., M.L. Stagnitto, R.K. Ray, M.A. Knowels, R. Harvey, G.E. Garske, 1993. Anticonvulsant properties of calcium channel blockers in mice: NMDLA and BAYK 8644-induced convulsions are potently blocked by the dihydropyridines. Epilepsia, 34: 372-380.

[14.] Van Luijtelaar, E.L.J.M., N. Ales, A.M.L. Coenen, 1995. Role of L-type calcium channel modulation in nonconvulsive epilepsy in rats. Epilepsia, 36(1): 86-92.

[15.] Wurpel, J.N., S. Iyer, 1994. Calcium channel blockers verapamil and nimodipine inhibit kindling in adult and immature rats. Epilepsia, 35: 443-449.

(1) Khayatnouri Mirhadi, (2) Iagmaie Pedram, (2) Hatefi Farzam

(1) Department of Pharmacology, Tabriz Branch, Islamic Azad University, Tabriz, Iran.

(2) Veterinary Student, Tabriz Branch, Islamic Azad University, Tabriz, Iran.

Corresponding Author

Khayatnouri Mirhadi, Department of Pharmacology, Tabriz Branch, Islamic Azad University, Tabriz, Iran.

E-mail: khayat.nouri@gmail.com mh.khayatnouri@iaut.ac.ir; Tel: 0098 914 300 5855
Table 1: Effect of different doses of verapamil on the type of
seizures induced by Primphos injection (percentage).

Type of seizures (percentage) Group    Low   Moderate   Severe

Primphos                               0     0          100
Verapamil 2.5 + Primphos               0     0          100
Verapamil 5 + Primphos                 0     30         70
Verapamil 10 + Primphos                10    30         60
Verapamil 20 + Primphos                30    40         30
Verapamil 40 + Primphos                50    40         10
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Title Annotation:Original Article
Author:Mirhadi, Khayatnouri; Pedram, Iagmaie; Farzam, Hatefi
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:7IRAN
Date:Jun 1, 2011
Words:2135
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