Abstract
Excitatory postsynaptic currents (EPSCs) were recorded with loose
patch electrodes placed over visualized boutons on the surface of
rat pelvic ganglion cells. At 34 degrees C the time to peak of the
EPSC was about 0.7 ms, and a single exponential described the declining
phase with a time constant of about 4.0 ms; these times were not
correlated with changes in the amplitude of the EPSC. The amplitude-frequency
histogram of the EPSC at individual boutons was well described by
a single Gaussian-distribution that possessed a variance similar
to that of the electrical noise. Nonstationary fluctuation analysis
of the EPSCs at a bouton indicated that about 120 ACh receptor channels
were available beneath boutons for interaction with a quantum of
ACh. The characteristics of these EPSCs were compared with the results
of Monte Carlo simulations of the quantal release of 9000 acetylcholine
(ACh) molecules onto receptor patches of density 1400 microns-2 and
0.41 micron diameter, using a kinetic scheme of interaction between
ACh and the receptors similar to that observed at the neuromuscular
junction. The simulated EPSC generated in this way had temporal characteristics
similar to those of the experimental EPSC when either the diffusion
of the ACh is slowed or allowance is made for a finite period of
transmitter release from the bouton. The amplitude of the simulated
EPSC then exhibited stochastic fluctuations similar to those of the
experimental EPSC.
- 9083664
- acetylcholine,
- animals,
- carlo
- cholinergic,
- ganglia,
- gov't,
- inbred
- kinetics,
- method,
- microelectrodes,
- monte
- non-u.s.
- patch-clamp
- presynaptic
- processes,
- rats,
- receptors,
- research
- stochastic
- strains,
- support,
- sympathetic,
- synaptic
- techniques,
- terminals,
- transmission,
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