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Effects of delta opioid antagonists on enkephalin-induced seizures
Abstract:
We examined the effect of opioid receptor antagonists on the seizure phenomena induced by specific delta opioid receptor agonist [D-Ser2,Leu5] enkephalyl-Thr (DSLET). The experiments have been performed in the anesthetized rats, and the DSLET-induced seizure phenomena were registered by electrocorticogram and electromyogram. It was demonstrated that two selective delta opioid receptor antagonists, ICI 152,129 and ICI 174,864 inhibited DSLET-induced epileptiform ECoG pattern and myoclonic contractions in a dose-related manner. An equimolar concentration of naloxone failed to antagonize the epileptiform effects of DSLET. It is concluded that delta opioid receptor agonist-induced seizure is mediated by delta receptors, since it can be blocked by delta opioid receptor antagonists. Evidently, delta opioid antagonists can be used as a good tool, in order to demonstrate a delta component in the seizure phenomena induced by other endogenous opioid peptides or their derivatives.
Insights
Selective delta opioid receptor antagonists effectively blocked seizures induced by the agonist DSLET in rats. This confirms delta opioid receptors mediate these seizure phenomena, suggesting antagonists can identify delta components in other opioid-induced effects.
Area of Science:
- Neuroscience
- Pharmacology
- Opiate Receptor Research
Background:
- Opioid receptor agonists can induce seizure phenomena.
- The specific role of delta opioid receptors in these seizures requires further elucidation.
Purpose of the Study:
- To investigate the effect of selective delta opioid receptor antagonists on seizures induced by the delta opioid receptor agonist [D-Ser2,Leu5] enkephalyl-Thr (DSLET).
- To determine if delta opioid receptors mediate DSLET-induced seizure phenomena.
Main Methods:
- Experiments were conducted on anesthetized rats.
- DSLET-induced seizure phenomena were monitored using electrocorticogram (ECoG) and electromyogram (EMG).
- The effects of selective delta opioid receptor antagonists (ICI 152,129 and ICI 174,864) and naloxone were assessed.
Main Results:
- Selective delta opioid receptor antagonists ICI 152,129 and ICI 174,864 dose-dependently inhibited DSLET-induced epileptiform ECoG patterns and myoclonic contractions.
- An equimolar concentration of naloxone did not antagonize the DSLET-induced epileptiform effects.
Conclusions:
- Seizures induced by the delta opioid receptor agonist DSLET are mediated by delta opioid receptors.
- Selective delta opioid receptor antagonists are effective tools for identifying the involvement of delta opioid receptors in seizure phenomena induced by other opioid peptides or derivatives.