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Tramadol, a centrally acting opioid: anticonvulsant effect against maximal electroshock seizure in mice
A Manocha1, K K Sharma, P K Mediratta
1Department of Pharmacology, University College of Medical Sciences and GTB Hospital, Delhi.
Abstract:
The present study was designed to investigate the pro- or anticonvulsant effect of tramadol using maximal electroshock (MES) test. An attempt was also made to determine the possible opioid receptor mechanism involved. MES seizures were induced through transauricular electrodes (60 mA, 0.2s) and the seizure severity was assessed by the duration of tonic hindlimb extensor phase. Intraperitoneal (i.p.) administration of tramadol resulted in a dose-dependent anticonvulsant action; the ED50 for the effect was 33 mg/kg. The anti-MES effect of tramadol was antagonized by the low doses (0.05 and 0.1 mg/kg, s.c.) of MR 2266, a selective kappa receptor antagonist and also by the high doses (1.0 and 5.0 mg/kg, i.p.) but not the low doses (0.1 and 0.25 mg/kg) of naloxone. The results suggest that the anti-MES effect of tramadol is mediated by kappa receptors, since MR 2266 and naloxone (in high doses) are known to block these receptors.
Insights
Tramadol exhibits a dose-dependent anticonvulsant effect in the maximal electroshock (MES) test. This anti-seizure action is primarily mediated through kappa opioid receptors.
Area of Science:
- Neuroscience
- Pharmacology
- Epilepsy Research
Background:
- Tramadol is an analgesic with known central nervous system effects.
- The precise mechanism underlying tramadol's potential anticonvulsant properties requires further elucidation.
- Opioid receptors are implicated in modulating seizure activity.
Purpose of the Study:
- To investigate the anticonvulsant effects of tramadol using the maximal electroshock (MES) test.
- To explore the involvement of opioid receptors in tramadol's anti-seizure activity.
Main Methods:
- Maximal electroshock (MES) seizures were induced in a preclinical model.
- Tramadol was administered intraperitoneally (i.p.) at various doses.
- The effects of tramadol were assessed in the presence of opioid receptor antagonists (naloxone and MR 2266).
Main Results:
- Tramadol demonstrated a dose-dependent anticonvulsant effect, with an ED50 of 33 mg/kg.
- The anticonvulsant activity of tramadol was significantly reduced by MR 2266, a kappa receptor antagonist.
- High doses of naloxone, which also interact with kappa receptors, partially antagonized tramadol's effect.
Conclusions:
- Tramadol possesses significant anticonvulsant properties.
- The anti-MES effect of tramadol is predominantly mediated via kappa opioid receptors.
- These findings suggest a novel therapeutic potential for tramadol in managing certain seizure disorders.