Neurotransmission in the auditory system.

Neurotransmitters and neuromodulators thought to be active on neurons in the cochlea, CN, and SOC have been reviewed. The variety of neurotransmitters and neuromodulators present and likely colocalized in these neurons are the chemical substrates that link morphologically and physiologically diverse neurons to process sound information. The impact of the limited number of neurotransmitters and neuromodulators in the auditory system is magnified by their interaction with structurally diverse receptors; thus great functional diversity is possible. Moreover, the effects of neurotransmitters and neuromodulators are not limited to synaptic transmission but serve as trophic agents for the establishment of neuronal circuitry during development and the rearrangement of synapses as a result of sensory experience or injury. An understanding of the neurochemical aspects of sensory processing at these diverse synapses then is of fundamental importance in understanding the organization of the auditory system.