Interactions between serotonin and cisapride on myenteric neurons.

Area of Science:

• Neurogastroenterology
• Pharmacology
• Cellular Electrophysiology

Background:

• Serotonin (5-HT) plays a crucial role in regulating gastrointestinal motility.
• Myenteric neurons in the guinea-pig small intestine are key targets for neurotransmitters like 5-HT.
• Understanding drug interactions with neurotransmitter systems is vital for developing effective treatments.

Purpose of the Study:

• To investigate the effects of cisapride on serotonin-induced responses in guinea-pig myenteric neurons.
• To elucidate the mechanism by which cisapride modulates neuronal activity and neurotransmitter release.

Main Methods:

• Intracellular recordings were performed on myenteric neurons.
• Serotonin (5-HT) was applied to assess its effects on neuronal excitability and synaptic transmission.
• Cisapride was administered to evaluate its modulatory actions on 5-HT responses.

Main Results:

• Serotonin elicited prolonged and transient depolarizations, along with presynaptic inhibition of acetylcholine release.
• Cisapride dose-dependently reduced or abolished both prolonged and transient 5-HT responses.
• Cisapride suppressed stimulus-evoked slow excitatory postsynaptic potentials (EPSPs) and reduced fast cholinergic EPSPs, suggesting presynaptic agonism at 5-HT receptors.

Conclusions:

• Cisapride significantly alters the electrophysiological effects of serotonin on myenteric neurons.
• The findings suggest cisapride acts as an agonist at presynaptic serotonergic receptors, modulating neuronal excitability and neurotransmitter release.
• This study provides insights into the complex interactions between cisapride and the serotonergic system in the enteric nervous system.