Multiple mechanisms of fast excitatory synaptic transmission in the enteric nervous system

The enteric nervous system (ENS) can control gastrointestinal function inde pendent of direct connections with the central nervous system. Enteric nerv es perform this important function using multiple mechanisms of excitatory neurotransmission in enteric ganglia. Fast excitatory synaptic transmission in the autonomic nervous system (ANS) is largely mediated by acetylcholine (ACh) acting at nicotinic cholinergic receptors but in the ENS there are n oncholinergic fast excitatory neurotransmitters. There are two broad types of neurons in the ENS: S neurons and AH neurons. S neurons are interneurons and motoneurons while AH neurons are sensory neurons. Three subsets of S n eurons in the myenteric plexus can be distinguished on the basis of the neu rotransmitters producing fast excitatory postsynaptic potentials (fEPSPs) i n each subset. In one subset, fEPSPs are mediated solely by ACh acting at n icotinic cholinergic receptors. In a second subset of S neurons, ATP acting at P2X purine receptors and ACh contribute to the fEPSP while in a third s ubset, fEPSPs are mediated by 5-hydroxytryptamine (5-HT) acting at 5-HT3 re ceptors and ACh. Some AH neurons also receive fast excitatory synaptic inpu t. The fEPSPs recorded from AH neurons are mediated ACh and also by glutama te acting at alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) re ceptors. Multiple mechanisms of fast excitatory synaptic transmission in th e ENS are likely to contribute to its capacity to regulate complex gastroin testinal functions. (C) 2000 Elsevier Science B.V. All rights reserved.