Variability of Excitatory Currents due to Single-Channel Noise, Receptor Number and Morphological Heterogeneity
✍ Scribed by J. TROMMERSHÄUSER; S. TITZ; B.U. KELLER; A. ZIPPELIUS
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 402 KB
- Volume
- 208
- Category
- Article
- ISSN
- 0022-5193
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✦ Synopsis
Patch clamp recordings of excitatory postsynaptic currents (EPSCs) in central neurons reveal large #uctuations in amplitudes and decay times of AMPA-receptor-mediated EPSCs. By using Monte Carlo simulations of synaptic transmission in brainstem interneurons, we tested several hypothesis that could account for the observed variability. The coe$cient of variation (CV) of 0.5 for miniature amplitudes cannot be explained by #uctuations in vesicle content or receptor distribution, but is traced to variations in receptor number, which is estimated as 77$39 receptors per bouton. As the variability of rise times re#ects #uctuations in size of the post-synaptic density and heterogeneity of the receptor distribution, the relatively small CV"0.37 of experimentally determined values points to a homogeneous arrangement of receptors. Within our model the large variability of decay times (CV"0.49) can only be explained by #uctuations in the transmitter time course (mean residence times of 0.4$0.13 ms), presumably resulting from heterogeneities in synaptic morphology. Hence, our simulations indicate that di!erent noise sources control the variability of amplitudes, rise and decay times. In particular, the distribution of decay times yields information about the synaptic transmission process, which cannot be obtained from other observables.