Delta opioid receptors mediate seizures produced by intrahippocampal injection of ala-deltorphin in rats.
The effects of the selective delta opioid receptor agonist, ala-deltorphin, microinfused into the dorsal hippocampus or into the locus coeruleus, on the electrocorticographic (ECoG) activity continuously quantified in its spectrum were studied in rats. The microinjection into the dorsal hippocampus of ala-deltorphin (0.03, 0.3 and 1.0 nmol) produced dose-dependent motor and ECoG epileptogenic disorders. The microinfusion of similar doses of ala-deltorphin into the locus coeruleus did not evoke motor and ECoG changes. Intrahippocampal injection of naltrindole (10 and 20 pmol) antagonized the epileptogenic effects induced by ala-deltorphin; also naloxone (20 and 50 pmol) was able to prevent the effects induced by ala-deltorphin, although with a minor potency. In conclusion, the present experiments show that ala-deltorphin is a useful tool to characterize central opioid effects mediated by delta receptors in the brain and suggest that the stimulation of this subtype of receptors in the hippocampus is responsible for epileptogenic effects of opiates.
De Sarro
G B
GB
Department of Experimental Medicine, Faculty of Medicine, Catanzaro, Italy.
Marra
R
R
Spagnolo
C
C
Nisticò
G
G
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects; D005071:Evoked Potentials / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects* / Q000503:physiopathology; D007211:Indoles / Q000494:pharmacology; D007267:Injections; D008125:Locus Coeruleus / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D009019:Morphinans / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives*; D009292:Narcotic Antagonists / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects* / Q000502:physiology; D017465:Receptors, Opioid, delta; D012640:Seizures / Q000139:chemically induced* / Q000503:physiopathology
D007211:Indoles; D009019:Morphinans; D009292:Narcotic Antagonists; D009842:Oligopeptides; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; C059567:deltorphin; D009270:Naloxone; D009271:Naltrexone; C055382:naltrindole