Serotonergic control of phrenic motoneuronal activity at the level of the spinal cord of the rabbit.
The role of serotonin (5-hydroxytryptamine, 5-HT)-mediated modulation of phrenic motoneuronal activity was evaluated by microapplication of 5-HT and methysergide into the phrenic nuclei of the rabbit. 5-HT facilitated phrenic nerve activity (PNA) considerably resulting in a long-lasting augmentation of the peak amplitude of integrated PNA. In contrast, the blockade of intrinsically active 5-HT by methysergide decreased PNA and led to a strong reduction of the peak amplitude of integrated PNA. MDL 72222 was ineffective. Blockade of 5-HT receptors by preceding administration of methysergide effectively abolished the effects of microinjected 5-HT. Respiratory timing was unaffected by both the agonist and the antagonist. These results suggest that a considerable portion of the facilitatory influence of caudal raphe nuclei on central respiratory activity takes place at the phrenic nuclei level.
Schmid
K
K
Department of Physiology and Pathophysiology, University of Mainz, Mainz, F.R.G.
Böhmer
G
G
Merkelbach
S
S
D000818:Animals; D008784:Methysergide / Q000494:pharmacology; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology; D012016:Reference Values; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014326:Tropanes / Q000494:pharmacology; D014628:Vagotomy
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D014326:Tropanes; D012701:Serotonin; C042253:bemesetron; D008784:Methysergide