5-Hydroxytryptamine involvement in the intrinsic control of oesophageal EMG activity.
The effects and the sites of action of 5-Hydroxytryptamine (5HT) were examined in transverse muscular strips of pigeon oesophagus. 5-Hydroxytryptamine (0.001 to 30 microM) induced a concentration-dependent excitatory effect on the EMG activity. This response was mainly characterized by an increase in burst frequency. The maximum 5-HT-induced excitatory effect was not altered by methysergide (10 microM), but was abolished by tetrodotoxin (3 microM). Excitatory response to 5-HT was partly opposed by atropine (1 microM), potentiated by 5-methoxy-N, N-dimethyltryptamine (1 microM) and was not altered by guanethidine (10 microM). These results indicate that 5-HT activates the pigeon oesophagus indirectly via neural elements and has no direct action on the smooth muscle cells. 5-HT is thought to stimulate three different intramural neuron types: excitatory cholinergic neurons, excitatory non-cholinergic neurons and inhibitory non-cholinergic non-adrenergic neurons. The action on these different neurons seems to be mediated via different receptors.
D000200:Action Potentials; D000818:Animals; D010856:Columbidae / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004576:Electromyography; D004947:Esophagus / Q000502:physiology*; D008784:Methysergide / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000502:physiology; D011985:Receptors, Serotonin / Q000502:physiology; D012701:Serotonin / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D018377:Neurotransmitter Agents; D011985:Receptors, Serotonin; D012701:Serotonin; D013779:Tetrodotoxin; D008784:Methysergide