Coupling between fibres involved in sensory nerve neuromata in cats.

Electrophysiological evidence has been obtained for coupling between pairs of fibres involved in 2 types of neuroma of a cutaneous sensory nerve in cats. A pair of fibres was taken to be coupled when an antidromic impulse in 1 fibre evoked an orthodromic impulse in the other. The fibres involved tended to be small diameter myelinated fibres and unmyelinated fibres. The coupling between a pair of fibres was stable over periods of several hours. Some of the coupled fibres had regenerated back to the skin and formed a functional sensory ending. These coupled responses can be explained by there being ephaptic interaction between fibres within the neuroma or they may be due to activity in retrograde sprouts of regenerating nerve fibres. Ephaptic interactions between fibres in a neuroma may be part of the explanation for abnormal sensibility, particularly pain sensibility, after peripheral nerve injury.