ABSTRACT
This chapter provides a brief overview of neurotransmission, with emphasis laid on signaling mechanisms at synapses. The key proteins of signal processing in chemical synapses are the neurotransmitter receptors. Their functional organization is decisively determined by interacting cell adhesion molecules. One distinguishes between ionotropic and metabotropic receptors. The classical example of a neurotransmitter interacting with both types of receptor is acetylcholine: its muscarinic receptors are of the metabotropic type, while its nicotinic receptors are of the ionotropic type. Ethyl alcohol stimulates inhibitory GABAA and blocks excitatory NMDA receptors, sharing these molecular targets with barbiturates. One distinguishes between ionotropic GABAA and metabotropic GABAB receptors. A structure resembling that of the nicotinic acetylcholine receptor is exhibited by the ionotropic receptors of the neurotransmitters serotonin, GABA, and glycine as well as by a still somewhat enigmatic receptor Zinc-Activated Channel. The major signal inducing neuromuscular synapse formation is transmitted by agrin.
