Combined morphological and electrophysiological description of connections between single primary afferent fibres and individual motoneurons in the frog spinal cord.

In experiments on the isolated frog spinal cord the relationship between the statistical properties of the unitary EPSP and the number of synaptic contacts was determined when the primary afferent fibre used in evoking the EPSP and the motoneuron in which it was recorded were both stained with HRP. The size of the chemical component of the EPSP corresponds to the number of presynaptic boutons. Less obvious numerical correlation exists between the number of contact zones and the number of binomial units.