Lateral Olivocochlear Efferent Function
The role of a specific set of nerve fibers in the auditory system
Our studies are based on the model of lateral olivocochlear efferent function shown in the figure below, where different transmitters act to change the “set-point” of the auditory nerve. This action provides increased sensitivity and increased dynamic range for the auditory nerve. Our experiments use lesions with neurotoxins such as MPTP to study the mechanisms of function and to model disorders caused by dysfunction.
Model of iaterai efferent sef-point adjustment of auditory nerve activity. The excitatory and inhibitory NTs are depicted on separate AN terminais for the purpose of illustration. Excitatory NTs = acetylcholine (Ach), dynorphin (Dyn), caicitonin gene-reiated peptide (CGRP) and inhibitory NTs = dopamine enkephalin (Enk), GABA. A=afferent terminal; E=efferent terminal; Glu = glutamate; GiuR = glutamate receptor, GABAR = GABA receptor; AChR = ACh receptor, NPR neuropeptide receptor.
(from Le Prell et al 2003)
Diagram illustrating a model of lateral olivocochlear (LOC) efferent set-point adjustment of auditory nerve (AN) activity at the inner hair cell (IHC) synapse.
• Top of the image: Inner Hair Cell releasing glutamate (Glu) at synapses with auditory afferent terminals.
• Bottom left: Afferent terminal (A) receives excitatory efferent input (E), which releases neurotransmitters:
• Ach (acetylcholine)
• Dyn (dynorphin)
• CGRP (calcitonin gene-related peptide)
• These bind to AChR and NPR on the afferent, reducing its excitability.
• Bottom right: A different afferent terminal receives inhibitory efferent input, which releases:
• Dop (dopamine)
• Enk (enkephalin)
• GABA
• These bind to GABAR and NPR, increasing afferent excitability in this example.
• GluR indicates glutamate receptors on the afferent terminal that mediate excitatory input from the IHC.
Caption summary:
The model shows how lateral efferent neurons release various neurotransmitters (excitatory or inhibitory) that modulate afferent neuron sensitivity to IHC glutamate signaling. This helps fine-tune auditory nerve activity. Terms include:
• A = afferent terminal
• E = efferent terminal
• GluR = glutamate receptor
• GABAR = GABA receptor
• AChR = acetylcholine receptor
• NPR = neuropeptide receptor
(Source: Le Prell et al., 2003)
