Morphophysiological characteristics of connexions between single ventrolateral tract fibres and individual motoneurones in the frog spinal cord.

In experiments on the isolated frog spinal cord, simultaneous intracellular recordings were performed from synaptically connected individual ventrolateral tract fibres and lumbar motoneurones. Statistical parameters of amplitude fluctuations of unitary excitatory postsynaptic potentials evoked by direct activation of presynaptic axons were compared with the number of synaptic contacts at the same connexions revealed by staining both pre- and postsynaptic elements with horseradish peroxidase. Close correspondence between the number of contacting boutons and that of release elements (n) determined from binomial relations was observed.