5-Hydroxytryptamine modulates central respiratory activity in the newborn rat: an in vitro study.
Respiratory activity was recorded in cervical ventral roots during in vitro experiments performed on superfused brainstem-cervical cord preparations from newborn rats aged 0-3 days. The effects of 5-HT agents added to the bathing medium on respiratory frequency were analysed. Adding 5-hydroxytryptamine (5-HT, 30 microM) or 5-HT precursors (either L-tryptophane, L-Trp, 50 microM, or 5-hydroxytryptophane, 5-HTP, 50 microM) elicited increases in respiratory frequency. Precursor effects were blocked by a 5-HT antagonist (methysergide, 70 microM) and significantly reduced by pretreatment with a 5-HT synthesis inhibitor (p-chlorophenylalanine, PCPA, i.p. 300 mg/kg at birth). Adding drugs known to block (methysergide, 40 microM) or to potentiate (fluoxetine, 100 microM) any endogenous 5-HT effects decreased or increased respiratory frequency, respectively. These results suggest that the 5-HT biosynthesis mechanisms remain functional in vitro and that a continuous release of endogenous 5-HT exerts excitatory modulation on the respiratory rhythm generator.
Morin
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D
Equipe Biologie des Rythmes et du Développement, URA CNRS 0205, Faculté des Sciences et Techniques St Jérôme, Marseille, France.
Monteau
R
R
Hilaire
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G
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D010134:Fenclonine / Q000494:pharmacology; D005473:Fluoxetine / Q000494:pharmacology; D066298:In Vitro Techniques; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology; D008784:Methysergide / Q000494:pharmacology; D051381:Rats; D012119:Respiration / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology; D014364:Tryptophan / Q000494:pharmacology
D012702:Serotonin Antagonists; D005473:Fluoxetine; D012701:Serotonin; D014364:Tryptophan; D010134:Fenclonine; D008784:Methysergide