Hippocampal theta activity after systemic administration of a non-peptide delta-opioid agonist in freely-moving rats: relationship to D1 dopamine receptors.
Hippocampal theta activity was acquired and processed off-line from digitized EEG recordings after subcutaneous (s.c.) administration of the non-opioid delta agonist BW 373U86 (0.5-2.5 mg/kg) in freely-moving rats. Relative theta power spectral analysis, implemented by a signal processing software, showed that BW 373U86 induced a dose-dependent increase in the slow component of theta band (Type 2 theta), while movement-related fast theta band (Type 1 theta) failed to show significant changes. Moreover, the increase in relative Type 2 theta power showed a maximal change at 1 mg/kg of BW 373U86, while higher doses, although effective in increasing relative Type 2 theta, induced locomotion and irregularly increased Type 1 hippocampal theta activity. The administration of 10.0 mg/kg of the delta antagonist Naltrindole (NLI) 30 min before BW 373U86, abolished hippocampal Type 2 theta increase. The rise of relative Type 2 theta power induced by BW 373U86 (1-2.5 mg/kg) was greatly attenuated by 0.1 mg/kg of the selective dopamine (DA) D1 antagonist SCH 23390. Administration of 0.1 mg/kg of SCH 23390 alone did not modify hippocampal Type 2 theta. These results indicate that delta receptors modulate the expression of hippocampal Type 2 theta and dopamine, through D1 receptors, exerts a permissive role on this influence.
Marrosu
F
F
Institute of Neurology, Faculty of Medicine and Surgery, University of Cagliari, Italy.
Cozzolino
A
A
Puligheddu
M
M
Giagheddu
M
M
Di Chiara
G
G
D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D001552:Benzazepines / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D008124:Locomotion; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000502:physiology*; D017465:Receptors, Opioid, delta / Q000819:agonists* / Q000037:antagonists & inhibitors; D013826:Theta Rhythm / Q000187:drug effects*
D001549:Benzamides; D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D009292:Narcotic Antagonists; D010879:Piperazines; D017447:Receptors, Dopamine D1; D017465:Receptors, Opioid, delta; C083877:BW 373U86; D009271:Naltrexone; C071262:SK&F 82958; C055382:naltrindole