Effects of selective mu- and delta-opioid peptides on kindled amygdaloid seizures in rats

Opioid systems seem to be implicated in the regulation of brain excitability, though in an apparently controversial way. In order to assess the involvement of mu- and delta-opioid receptors in the anti-epileptogenic properties of opioids, i.v. administrations of morphine, and of DAGO (Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol) and DTLET (Tyr-D-Thr-Gly-Phe-Leu-Thr), two peptides presenting selective agonist properties towards respectively the mu and the delta receptors, were performed on fully kindled rats. It is concluded that the mu- rather than the delta-receptors are implicated in the limitation of amygdaloid kindled seizures.