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ISSN: 0975-8585 Anxiolytic Effect of Ondansetron, a 5-HT 3 Antagonist on male albino mice in the Elevated Plus Maze April-June 2013 RJPBCS Volume 4 Issue 2 Page No

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ISSN: 0975-8585 Anxiolytic Effect of Ondansetron, a 5-HT 3 Antagonist on male albino mice in the Elevated Plus Maze April-June 2013 RJPBCS Volume 4 Issue 2 Page No
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    ISSN: 0975-8585    April-June 2013 RJPBCS Volume 4 Issue 2 Page No. 1665   Research Journal of Pharmaceutical, Biological and Chemical Sciences  Anxiolytic Effect of Ondansetron, a 5-HT 3  Antagonist on male albino mice  in the Elevated Plus Maze Lourdu Jafrin A *1 , Shanthi M 2 , and Meher Ali R 1   1 Department of Pharmacology, Sri Manakula Vinayagar Medical College, Puducherry, India. 2 Institute of Pharmacology, Madurai Medical College, Tamil Nadu, India. ABSTRACT Anxiety affects one-eighth of the total population world-wide and has become an important area of psychopharmacological research during this decade. Ondansetron a selective 5HT-3 antagonist commonly used as an antiemetic has been claimed to have psychotropic effects. The   aim of this study is to evaluate the anxiolytic and sedative properties of ondansetron. Male albino mice were treated with ondasetron (0.04, 0.08, 0.16 mg/kg ), distilled water and diazepam intraperitoneally and the anxiolytic effect was evaluated using elevated plus maze. The spontaneous locomotor activity of mice after administering ondansetron (0.08, 0.16 mg/kg) was also tested using the actophotometer. Ondansetron showed significant anxiolysis at doses of 0.08mg/kg and 0.16mg/kg with increase in time spent in open arm(p<0.001)and increase in open arm entries (p<0.01). Ondansetron showed no significant(p > 0.05) decrease in counts in the actophotometer when analysed (p > .05). Hence ondansetron showed anxiolytic effects and had no sedative properties.  Keywords: anxiety disorders, serotonin antagonist, elevated plus maze , ondansetron *Corresponding author       ISSN: 0975-8585    April-June 2013 RJPBCS Volume 4 Issue 2 Page No. 1666   INTRODUCTION Anxiety disorders are among the most prevalent psychiatric disorders in the general population. These disorders are associated with significant morbidity and affect their routine day to day activities. Generalized anxiety disorders occur in 4-6 % of the population and are more common in women [1]. Anxiety disorders are also more common in children and adolescents occurring in 13% of young people [2]   . Anxiety is a feeling of apprehension, uncertainty and fear without apparent stimulus, associated with physiological changes like tachycardia, sweating and tremor. There is no identifiable triggering stimulus in anxiety. Anxiety is a normal reaction to stress. When anxiety becomes excessive, it falls under the classification of anxiety disorder. Three major neurotransmitters are associated with anxiety namely, norepinephrine, serotonin and gamma aminobutyric acid (GABA). Most of the available drugs to date reduce anxiety by modulating one of the above neuro transmitter mechanisms. There are also minor neurotransmitters which are under research to help patients with anxiety[3].   Some of the available drugs are selective serotonin reuptake inhibitors, selective norepinephrine reuptake inhibitors, benzodiazepines, beta adrenergic antagonists and barbiturates. Newer drugs like melatonin and hydroxyzine are also used. As these drugs have to be used on a prolonged basis chances of adverse effects like impotence, weight gain and psychomotor impairment are inevitable. Some of the herbal preparations which are used to reduce the ill effects of stress are Ocimum sanctum (Tulsi) , Withania somnifera ( Ashwagandha) , Altingia excelsa , Diospyros peregrina , Seleginella bryopteris( Sanjeevani) , Panax ginseng [4-6].   Given the above difficulties in administering anxiolytics, untiring efforts have been put into the discovery of newer anxiolytics with fewer adverse effects and without psychomotor impairment. This study is an effort in the above direction in the interest of the society at large. Ondansetron a well known 5HT 3  antagonist, widely used as an antiemetic has been claimed with a number of other uses in the realm of psychopharmacology. Evidence has been mounting over the fact that 5-HT (serotonin) acting through 5HT 3  receptor can influence behavior relevant to anxiety, schizophrenia and cognitive disorders. Ondansetron has also been found to be beneficial in the management of postcardiotomy delirium, morphine discontinuation phenomena, vertigo and intentional tremor.    ISSN: 0975-8585    April-June 2013 RJPBCS Volume 4 Issue 2 Page No. 1667   Serotonin plays a key role in the pathophysiology of anxiety and ondansetron being a serotonin antagonist was selected to study its anxiolytic and sedative properties in comparison with diazepam, a well known anxiolytic. MATERIALS AND METHODS The study was conducted for a period of eight months after obtaining ethical clearance from the institutional animal ethical committee, Madurai Medical College, Madurai. CPSCEA guidelines were adhered to throughout the study. Animals Inbred male albino mice from central animal house 14-20 weeks old and weighing 24(+2) g were included in the study. Animals were fed with standard pellet diet and water ad libitum . Twelve hour light-dark cycle was maintained and experiments carried out in the light phase. The mice were housed in polypropylene cages with six animals in each cage. Drugs Diazepam (Ranbaxy) was diluted to obtain a solution of concentration 0.01mg/ml and was administered intraperitoneally at the dose of 1mg/kg. Ondansetron was administered intraperitoneally at the graded doses of 0.04 mg / kg ,0.08 mg / kg and 0.16 mg / kg . Distilled water was used as vehicle control. Elevated Plus Maze The elevated plus maze apparatus consisted of two open (30 cm× 5 cm× 1 cm) and two closed (30 cm× 5 cm× 15 cm) arms, extending from a central platform (5 cm × 5cm) and elevated to a height of 50 cm above the floor. The entire wooden maze was painted black and surrounded by similar looking walls. Lighting was kept constant and to a minimum by a 15 watt bulb hung 1.5 m from above. Actophotometer The Digital actophotometer is designed to study the spontaneous locomotor activity in small animals like mice or rats. This apparatus uses optical sensors and emitters to record the horizontal movement of the animals on a four digit electronic counter display. METHODOLOGY Elevated Plus Maze for anti anxiety effect 30 male albino mice were divided into 5 groups of 6 animals in each group namely control, standard, test 1, test 2 and test 3 groups.    ISSN: 0975-8585    April-June 2013 RJPBCS Volume 4 Issue 2 Page No. 1668   Animals were assigned randomly to the control or treatment groups and only naive mice were used. All animals used were weighing between 24 and 26 g. Animals with a greater weight were excluded since fat distribution might change the distribution of compounds with a high volume of distribution (e.g. diazepam) and therefore influence the pharmacological response. Animals with 0% time spent on open arms or presenting with clear symptoms of abnormal behavior (e.g. no movement at all in home cage) were excluded from the experiment prior to statistical evaluation and replaced by a new, randomly chosen animal. The animals were allowed to adapt to the environment at least for one hour prior to the experiment. Lighting was kept constant.The control group animals were given distilled water i.p, the standard group of animals received inj.Diazepam 1 mg/kg i.p. The test 1, test 2 and test 3 group of animals received inj.Ondansetron in the doses of 0.04 mg / kg i.p, 0.08 mg / kg i.p and 0.16 mg / kg i.p respectively. After 30 minutes of drug administration mice were individually placed on the center of the elevated plus maze facing a closed arm, and the number of entries and the time spent in closed and open arms were recorded during a 5 min observation period. Arm entries were considered as entry only if all four paws enter into an arm. The observations wer e tabulated and analysed statistically using unpaired‘t’ test.   Spontaneous locomotor activity by Actophotometer The same animals used previously for anxiolytic effect were used after a wash out period of 15 days. These 30 male albino mice were grouped into five groups with six animals in each. The total number of counts made by each animal in the actophotometer for a period of 10 min was calculated. The control group of animals were administered inj.Distilled water i.p, the standard group of animals were given inj.Diazepam 1 mg /kg i.p, the test groups 1, 2 and 3 were given inj.Ondansetron in the dose of 0.04 mg / kg i.p , 0.08 mg / kg i.p and 0.16 mg / kg i.p respectively. After 30 min of drug administration, spontaneous locomotor activity for each animal for a period of 10 min was calculated and the observations were tabulated and analyzed statistically by using unpaired “t” test. RESULTS In the present study, 30 male albino mice were selected and were evaluated for anti anxiety and sedative effects. Anti anxiety effect was evaluated by elevated plus maze method and sedative effect was evaluated by spontaneous locomotor activity in actophotometer.    ISSN: 0975-8585    April-June 2013 RJPBCS Volume 4 Issue 2 Page No. 1669   Anti anxiety effect Anti anxiety effect was evaluated using elevated plus maze. The time spent in the open arm and also the number of entries into the open arm was noted in the control, standard and test groups. Time spent in open arm The time spent in open arm for control group of mice was 11+ 3.17 seconds. The time spent in open arm for standard group was 98 + 7.97 seconds. The time spent in open arm for test groups (1, 2, 3) was 18.83 + 3.24, 53.83 + 1.42 and 54.83 + 2.74 seconds respectively (table & chart 1). The results were tabulated and analysed using unpaired student’s “t” test. The anti anxiety effect was not statistically significant for the test group 1 (P = 0.115) in comparison with control group but was statistically significant for the test group 2 and group 3(P < 0.001) in comparison with control group. The anti anxiety effect was statistically significant for the standard group ( P < 0.001 ) in comparison with control group. Number of entries into open arm The number of entries into open arm for control group was 2.16 +0.60, for standard group was 14.5 + 2.05, for test groups (1, 2, 3 ) were 3.83 + 0.60, 6.67 + 1.05 and 7.67 + 1.23 (table & chart 2) respectively (fig 2). The results were tabulated and analysed using unpaired student’s “t” test . The anti anxiety effect was not statistically significant for the test group 1 ( P >0.05) in comparison with control group. The anti anxiety effect was statistically significant for the test group 2 (P < 0.01) and test group 3 ( P < 0.01) in comparison with control group. The anti anxiety effect was statistically significant for the standard group (P < 0.001) in comparison with control group. Spontaneous locomotor activity Sedative activity was evaluated by using Actophotometer. The spontaneous locomotor activity made by a mouse was noted in control, standard and test group before and 30 min after the administration of control, standard and test drugs. The average number of counts before and after 30 min for control group of mice was 623.17 + 23.75 and 626.17 + 34.70. The average number of counts before and after 30 min for standard group of mice was 630.83 + 18.43 and 346 + 13.93. The average number of counts before and after 30 min for test groups ( 1, 2, 3 ) was 603.33 + 11.83 and 609.67 + 19.78, 606.67 + 24.91 and 612.33+ 31.22, 615.17 + 16.48 and 623+ 24.18 (table & chart 3) respectively . The results were tabulated and analysed using unpaired student’s “t” test . The sedative effect was not statistically significant for the test groups (1, 2, 3) after 30 min of drug administration in
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