Distributions of EPSP Latency at Different Group Ia-Fiber-Alpha-Motoneuron Connections

1. Distributions of synaptic latency of single spike-triggered excitatory postsynaptic potentials (EPSPs) have been compared at different group Ia-fiber-alpha-motoneuron connections in the cat.

2. These distributions differ in standard deviation. When the latencies at different connections are measured from the terminal potential, which may signal the arrival of the Ia-fiber impulse in the terminals, the mean is also found to vary from connection to connection.

3. The mean and standard deviation exhibit a significant positive linear correlation. It can be shown that the minimum latency for all these distributions is about the same.

4. The amplitude of averaged EPSPs at these connections was found to be closely related to parameters of the latency distribution.

5. Latency of the averaged EPSP was found to be intermediate between the minimum and mean latency observed in single trials.

6. These variations in distribution of latencies may result from the action of different numbers of release sites (e.g., boutons) at different connections. However, differences in characteristics of transmitter release at different connections have not been ruled out.