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Estimating use-dependent synaptic gain in autonomic ganglia by computational simulation and dynamic-clamp analysis
Diek W Wheeler1, Paul H M Kullmann, John P Horn
1Department of Neurobiology, University of Pittsburgh School of Medicine, E1440 Biomedical Science Tower, Pittsburgh, PA 15261, USA. wheeler@mpih-frankfurt.mpg.de
Journal of Neurophysiology
|June 24, 2004
Summary
Synaptic gain in the sympathetic nervous system amplifies neural signals, enhancing homeostatic control of blood pressure and temperature. This amplification arises from synaptic convergence and plasticity in autonomic ganglia.
Area of Science:
- Neuroscience
- Computational Biology
- Physiology
Background:
- Biological gain mechanisms are crucial for signaling pathway regulation.
- In the sympathetic nervous system, sensory-motor feedback loops are vital for homeostasis.
- Synaptic gain in autonomic ganglia influences blood pressure and temperature regulation.
Purpose of the Study:
- To investigate how synaptic convergence and plasticity generate synaptic gain in autonomic ganglia.
- To understand the mechanisms enhancing homeostatic control through neural signaling.
- To model and measure synaptic gain in sympathetic neurons.
Main Methods:
- Utilized a conductance-based computational model of sympathetic neurons.
- Simulated postsynaptic responses to presynaptic activity patterns.
- Employed dynamic clamp to stimulate dissociated bullfrog sympathetic neurons with virtual synapses.
Main Results:
- Simulations showed up to threefold amplification in postsynaptic spike output.
- Synaptic gain depended on nicotinic synapse number/strength, firing rate, facilitation, and muscarinic/peptidergic excitation.
- Experimental results aligned with simulations, showing gain increased with nicotinic convergence.
- Postsynaptic effects, including gain decline, were observed and partially blocked by Cd2+.
Conclusions:
- Synaptic convergence and plasticity generate significant synaptic gain in autonomic ganglia.
- This gain mechanism enhances homeostatic regulation within the sympathetic nervous system.
- Neural circuit variations allow sympathetic ganglia to function as relays, amplifiers, or switches.