Modulation of non-adrenergic non-cholinergic inhibitory transmission in rat duodenum: role of opiates and 5-hydroxytryptamine.
In rat duodenal segments in vitro, electrical field stimulation induced a TTX-sensitive relaxation in the presence of atropine and guanethidine. A correlation between the amplitude of the evoked response and stimulus frequency was observed. Opioid peptides DAGO, DPDPE and DYN caused a dose-dependent increase in the amplitude of the response to EFS. Naloxone shifted to the right the dose-response curves for each opioid peptide significantly enhancing the ED50 values. The amplitude of the response to EFS was enhanced, dose-dependently, also in the presence of 5-HT. Such an effect induced by 5-HT was prevented by 5-HT receptor desensitization, but persisted unchanged after naloxone pretreatment. Opioids failed to affect the response to EFS after 5-HT receptor desensitization. Results suggest that in rat duodenum opioids modulate NANC inhibitory neurotransmission, indirectly the release of 5-HT.
Postorino
A
A
Dipartimento di Biologia Cellulare e dello Sviluppo, Corso Tukory, Palermo, Italia.
Serio
R
R
Mulè
F
F
Adamo
E B
EB
Di Giovanni
G
G
Marini
R
R
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001341:Autonomic Nervous System / Q000187:drug effects*; D004386:Duodenum / Q000187:drug effects / Q000294:innervation*; D004399:Dynorphins / Q000494:pharmacology; D004558:Electric Stimulation; D004723:Endorphins / Q000502:physiology*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D005769:Gastrointestinal Motility / Q000187:drug effects; D006145:Guanethidine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology
D000700:Analgesics; D004723:Endorphins; D004745:Enkephalins; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D012701:Serotonin; D009270:Naloxone; D013779:Tetrodotoxin; D004399:Dynorphins; D001285:Atropine; D020881:Enkephalin, D-Penicillamine (2,5)-; D006145:Guanethidine