Different mechanisms are involved in the respiratory depression and analgesia induced by neurotensin in rats.
The tridecapeptide neurotensin (NT), injected intracerebroventricularly in rats, induced a naloxone-insensitive and dose-dependent analgesia (tail-flick test), the ED50 being 3.22 nmol/animal. Higher doses induced a dose-dependent respiratory depression, mostly accounted for by a reduction of frequency; the ED50 for this action was 144.6 nmol/animal. In contrast to analgesia, the respiratory depression was antagonized by naloxone, suggesting the possibility that NT and opioid systems might interact at the level of respiration-related nuclei.
D000698:Analgesia; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D007276:Injections, Intraventricular; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009496:Neurotensin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012119:Respiration / Q000187:drug effects*; D013997:Time Factors
D009270:Naloxone; D009496:Neurotensin