The Journal of Neuroscience, September 15, 2000, 20(18):6760-6772
Temporal Pattern Dependence of Neuronal Peptide Transmitter
Release: Models and Experiments
Vladimir
Brezina,
Paul J.
Church, and
Klaudiusz R.
Weiss
Department of Physiology and Biophysics and Fishberg Research
Center for Neurobiology, Mount Sinai School of Medicine, New York, New
York 10029
In this paper we construct, on the basis of existing experimental
data, a mathematical model of firing-elicited release of peptide
transmitters from motor neuron B15 in the accessory radula closer neuromuscular system of Aplysia. The model
consists of a slow "mobilizing" reaction and the fast release
reaction itself. Experimentally, however, it was possible to measure
only the mean, heavily averaged release, lacking fast kinetic
information. Considered in the conventional way, the data were
insufficient to completely specify the details of the model, in
particular the relative properties of the slow and the unobservable
fast reaction. We illustrate here, with our model and with additional
experiments, how to approach such a problem by considering another
dimension of release, namely its pattern dependence. The mean release
is sensitive to the temporal pattern of firing, even to pattern on time
scales much faster than the time scale on which the release is
averaged. The mean release varies with the time scale and
magnitude of the pattern, relative to the time scale and nonlinearity
of the release reactions with which the pattern interacts. The type and
magnitude of pattern dependence, especially when correlated
systematically over a range of patterns, can therefore yield
information about the properties of the release reactions. Thus,
temporal pattern can be used as a probe of the release process, even of
its fast, directly unobservable components. More generally, the
analysis provides insights into the possible ways in which such pattern
dependence, widespread especially in neuropeptide- and
hormone-releasing systems, might arise from the properties of the
underlying cellular reactions.
Key words:
synaptic transmission; neurotransmitter; neuropeptide; transmitter release; firing pattern; temporal pattern dependence; mathematical modeling; Aplysia
Copyright © 2000 Society for Neuroscience 0270-6474/00/20186760-13$05.00/0
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