Serotonin and cervical respiratory motoneurones: intracellular study in the newborn rat brainstem-spinal cord preparation.
Previous experiments performed in the in vitro newborn rat brainstem-spinal cord preparation reported that the addition of serotonin (5-HT, 30-50 microM) to the bathing medium induced increases in the respiratory frequency and a large tonic discharge on all the cervical ventral roots. The aim of the present work was to define whether the 5-HT-induced tonic discharge involved respiratory or non-respiratory motoneurones. Intracellular recordings demonstrated that cervical (C2) motoneurones (n = 27) were depolarized by 5-HT but that the 5-HT-induced tonic discharge was mainly due to recruitment of silent motoneurones (n = 18) which fired permanently (15/18; 17 +/- 3 Hz) under 5-HT. The respiratory motoneurones (n = 9) retained a phasic inspiratory discharge (5/9), even if some (4/9) occasionally exhibited a few spikes during expiration. Therefore, it is concluded that the 5-HT-induced tonic discharge is unlikely to have functional significance in respiration.
Morin
D
D
Equipe Biologie des Rythmes et du Développement, URA-CNRS 0205, Faculté des Sciences et Techniques St Jérôme, Marseille, France.
Monteau
R
R
Hilaire
G
G
D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D012119:Respiration; D012701:Serotonin / Q000494:pharmacology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
D012701:Serotonin