Mechanisms of excitatory synaptic transmission in the enteric nervous system.

The enteric nervous system can control gastrointestinal function independent of direct connections with the central nervous system. Enteric nerves can perform this task as there are multiple mechanisms of excitatory neurotransmission in enteric ganglia. There are two broad types of excitatory synaptic transmission, fast and slow excitatory synaptic responses. Fast excitatory postsynaptic potentials (fEPSPs) are recorded from "S" type neurons and some AH type neurons. S neurons are interneurons and motorneurons while AH neurons are intrinsic sensory neurons. Slow excitatory postsynaptic potentials (sEPSPs) can be recorded from some S neurons and also from AH type neurons. The fEPSPs recorded from S neurons and mediated largely by acetylcholine acting at nicotinic cholinergic receptors (nAChRs). However, ATP acting at P2X purine receptors contributes to the fEPSP in many S neurons. The fEPSPs recorded from AH neurons are also mediated largely by nAChRs but glutamate acting at AMPA receptors contributes to fEPSPs in some AH neurons. The sEPSPs in AH neurons are mediated by one or more neuropeptides and 5-hydroxytryptamine. The sEPSPs in AH neurons are due to inhibition of two types of resting potassium channels and activation of a chloride channel or a nonspecific cation channel. The multiple mechanisms of excitatory synaptic transmission in the enteric nervous system contribute to its capacity to regulate complex gastrointestinal functions.