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Indian Journal of Pharmacology, Vol. 38, No. 4, July-August, 2006, pp. 283-284 Research Letter Effect of single dose thalidomide on stress induced rise of plasma corticosterone in rats Patil CR, Bhise SB, Bhatia MS R. C. Patel College of Pharmacy, Karvand Naka, Shirpur-425 405, Government College of Pharmacy, Vidyanagar, Karad-416 124 and Bharati Vidyapeeth's College of Pharmacy, Kolhapur, Maharashtra Code Number: ph06074 The concept of bi-directional communication between the immune system, endocrine system, ANS and CNS is now well accepted[1].Many neurotransmitters are known to alter the immune status through receptor mechanisms on the immune system cells. In return, many cytokines secreted by immune system cells have the ability to affect the activity of CNS. Interaction between the hypothalamus, pituitary and adrenals, (HPA axis) can be considered as an important example of such a bi-directional interaction between these systems.[1] Different classes of CNS active drugs like sedatives, anxiolytics, antidepressants and antipsychotics are also known to modulate the immune system activity. Some of these agents, which possess immunomodulatory activity, are known to affect the HPA axis activity.[2],[3] Thalidomide, the worst known teratogen, is a sedative as well as an immunomodulator and acts through multiple mechanisms. The most accepted mechanism of action for thalidomide is the inhibition of the synthesis of a proinflammatory cytokine (TNF-a), by reducing the half-life of related m-RNA.[4],[5] However, many clinical as well as in vitro studies have shown that the inhibitory effect of thalidomide on TNF-a is not consistent.[6] This effect may depend upon the patient's immune status or the stimulants as well as target cells used for TNF-a release in the in vitro assays.[6] None of the other reported effects of thalidomide, such as antiangiogenesis or teratogenesis, explains the mechanism of its immunomodulatory potency. There are certain studies which indicate the possible involvement of serotonin in the sedative and anxiolytic action of this drug.[7] Thalidomide is also known to affect certain endocrine secretions like follicle stimulating hormones, thyroid stimulating hormone, prolactin, corticotropin and thyroid secretions . However, whether thalidomide affects the activity of HPA axis remains to be studied. In the present investigation, the effect of thalidomide on plasma corticosterone levels in normal and stressed rats was studied. The plasma corticosterone level is an indicator of the activity of HPA axis in rats.[8] A major physiological response to psychological or physical stress is the activation of the HPA axis, which leads to an increase in levels of corticosteroids in circulation. Such an increase in the plasma corticosterone levels can be induced in experimental animals such as rats and rabbits through brief restraint stress. Short-term restraint stress procedures are believed to be largely psychological in nature and are known to affect various endocrine parameters.[8] In the present study, the effect of single dose thalidomide on plasma corticosterone levels was evaluated in restraint stressed and normal Wistar rats. After procurement, adult male Wistar rats, weighing 275-300 g, were maintained for seven days under controlled conditions of light (lights on from 8.00 am to 20.00 pm) and temperature (22°C). Food and water were available ad libitum . The procedures followed the guidelines recommended by CPCSEA for the care and use of laboratory animals. The Institutional Animal Ethical Committee approved the study. On the day of experiment, the animals were divided into four groups, each consisting of 7 rats; as control group, stress group, 100 mg/kg thalidomide treated group, 100 mg/kg thalidomide treated and stressed group. The dose of 100 mg/kg of thalidomide was selected, based on our prior study (results not shown), which was found to significantly reduce the spontaneous activity in mice and rats. The control group received 1% carboxymethyl cellulose (CMC) solution, while the thalidomide group was given 100 mg/kg thalidomide suspended in 1% CMC by oral gavage one hour prior to the collection of blood samples. Exactly after an hour, the rats were lightly anesthetised with ether and 2 ml blood samples were collected by cardiac puncture in a syringe containing 0.2 ml of heparin (5000 IU/ml) and processed for determination of plasma corticosterone. The rats in the 'stress group' were given 1% CMC solution and those in the 'thalidomide treated and stressed group' were administered 100 mg/kg thalidomide suspended in 1% CMC by oral gavage, immediately before induction of stress. The rats were stressed by restraint in plastic tubes of variable length, having a diameter of 6.5 cm. Care was taken not to compress the body of animals during restraint. The rats were restrained for one hour between 10.00 am and 12.00 noon. Immediately after restraint, they were anesthetised with ether and 2 ml blood samples were collected as mentioned earlier. The complete procedure of anesthesia and blood sampling was done strictly within 90 seconds after restraint and the plasma was separated in a temperature-controlled centrifuge at 4°C and stored at -20°C till analysis. The plasma corticosterone levels were determined by the HPLC method as described by Ling et al,[9] with certain modifications. A Jasco binary gradient Liquid Chromatography system comprising PU-2080 Plus pumps, MX-2080-31 solvent mixing module, UV2075 Plus UV/Visible detector, Rheodyne-7725i injector port with a 20 ml loop and Thermoquest 5 m Hypersil ODS (250 x 4.6 mm) column was used for corticosterone estimation. The solvent system used was acetonitrile: methanol: phosphoric acid (0.2M) (25:25:50), using betamethasone as an internal standard. The means of the plasma corticosterone levels in different groups were compared using one-way ANOVA. P < .05 was considered statistically significant. The difference in the mean plasma corticosterone levels in the study groups was statistically significant as determined by ANOVA ( P < .001, n=7 in each group). The level of plasma corticosterone after one hour restraint stress (120±15 ng/ml) was found to be significantly ( P < .001) higher than that of control group (33±2.3 ng/ml). Thalidomide 100 mg/kg b.w., by oral route, did not significantly alter the plasma corticosterone levels (37±2.9 ng/ml). However, thalidomide (100 mg/kg) was found to significantly reduce the stress induced rise in the plasma corticosterone (46±9.9 ng/ml) compared to the stress alone group. The results of our study show that thalidomide reduced stress-induced increase in plasma corticosterone levels. The CNS active drugs such as anxiolytics, sedatives, hypnotics, antidepressants and antipsychotics are supposed to alter normal and stress-induced plasma corticosterone levels by affecting serotonin, dopamine, adrenaline, acetylcholine or GABA neurotransmitter turnover or by directly binding to their receptors in CNS and peripheral organs.[1] However, thalidomide is not known to bind to the receptors of any of these neurotransmitter. The corticosterone reducing effects of this drug may involve the serotonergic mechanism, which is probably involved in its sedative and anxiolytics action.[7] It has been found that thalidomide and its analogue supidimide inhibit serotonin release.[7] Also, corticosteroids are involved in stress-induced alterations in immune status.[3] However, in the present investigation simultaneous estimations of serotonin levels have not been done. It is proposed that an alteration in stress induced increase in plasma corticosterone levels, caused by thalidomide, may have a role in its pharmacodynamics. It will be interesting to investigate the effects of chronic treatment with thalidomide on serotonin concentrations in circulation and in CNS along with its effects on stress-induced alterations in the immunity and modulation of these effects by other drugs known to affect serotonin. Acknowledgments The authors are thankful to Dr. F.V. Manavi (Principal), Prof. A.D. Taranalli (Vice-Principal), KLE College of Pharmacy, Belgaum and Dr. H.N. More (Principal), B.V. College of Pharmacy, Kolhapur for their valuable support. The sample of thalidomide was generously supplied by Dr. P.D. Khullar (Manager, R & D, Dabur Research Foundation, Ghaziabad, UP, India) and Digambar Nigade, R & D, Dabur Research Foundation, Ghaziabad, UP, India).References
Copyright 2006 - Indian Journal of Pharmacology |
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