Actions of 5-hydroxytryptamine on myenteric neurons in guinea pig gastric antrum.
Intracellular recording methods were used to study the actions of 5-hydroxytryptamine (5-HT) on 257 myenteric neurons in the guinea pig gastric antrum. Application of 5-HT caused three types of postsynaptic responses. A fast-activating depolarizing response was accompanied by a decreased input resistance and desensitized quickly to repeated applications. It was mediated by a 5-HT3 receptor. A slowly activating depolarization, accompanied by an increase in the input resistance and enhancement of the excitability, was mainly observed in after hyperpolarizing/type 2 neurons. It was suppressed by the prokinetic benzamide compound renzapride, while classical 5-HT1-4 receptor antagonists had no effect, suggesting the involvement of a 5-HT1p receptor as described in small intestinal neurons. A long-lasting hyperpolarizing response, accompanied by a decreased input resistance, was observed in a small subset of neurons. This response seemed to be mediated by a 5-HT1a receptor. Superfusion of 5-HT caused a dose-dependent inhibition of the stimulus-evoked nicotinic cholinergic fast excitatory postsynaptic potential (EPSP), which was mediated by a presynaptic 5-HT1a receptor. 5-HT also presynaptically inhibited the slow EPSP.
Tack
J F
JF
Department of Physiology, College of Medicine, Ohio State University, Columbus 43210.
Janssens
J
J
Vantrappen
G
G
Wood
J D
JD
D000818:Animals; D004594:Electrophysiology; D006168:Guinea Pigs; D008297:Male; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects*; D009433:Neural Inhibition; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D011706:Pyloric Antrum / Q000187:drug effects* / Q000502:physiology; D011930:Reaction Time; D012701:Serotonin / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology
D012701:Serotonin