title: Modeling the resonant release of synaptic transmitter by hair cells as an example of biological oscillators with cooperative steps.
abstract: The initial synapses of the auditory system, which connect hair cells to afferent nerve fibers, display two unusual features. First, synaptic transmission occurs in a multiquantal fashion: the contents of multiple synaptic vesicles are discharged simultaneously. Second, synaptic transmission may be tuned to specific frequencies of stimulation. We developed a minimal theoretical model to explore the possibility that hair-cell synapses achieve both multiquantal release and frequency selectivity through a cooperative mechanism for the exocytotic release of neurotransmitter. We first characterized vesicle release as a four-step cycle at each release site, then generalized the result to an arbitrary number of steps. The cyclic process itself induces some degree of resonance, and may display a stable, underdamped fixed point of the release dynamics associated with a pair of complex eigenvalues. Cooperativity greatly enhances the frequency selectivity by moving the eigenvalues toward the imaginary axis; spontaneously oscillatory release can arise beyond a Hopf bifurcation. These phenomena occur both in the macroscopic limit, when the number of release sites involved is very large, and in the more realistic stochastic regime, when only a limited number of release sites participate at each synapse. It is thus possible to connect multiquantal release with frequency selectivity through the mechanism of cooperativity.
authors.affiliation: Laboratory of Sensory Neuroscience, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY, 100656399, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Andor-Ardó
authors.forename: A J
authors.initials: AJ
authors.lastname: Hudspeth
authors.forename: Marcelo O
authors.initials: MO
authors.lastname: Magnasco
authors.forename: Oreste
authors.initials: O
authors.lastname: Piro
mesh_terms: D001683:Biological Clocks; D055592:Biophysical Phenomena; D006198:Hair Cells, Auditory / Q000502:physiology*; D008390:Markov Chains; D008959:Models, Neurological; D018377:Neurotransmitter Agents / Q000378:metabolism; D017711:Nonlinear Dynamics; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000502:physiology
chemical_list: D018377:Neurotransmitter Agents