Journal of Neurophysiology, Vol 41, Issue 4 885-895, Copyright © 1978 by APS
Specificity of afferent and efferent regeneration in the cockroach: establishment of a reflex pathway between contralaterally homologous target cells
C. R. Fourtner, C. D. Drewes and T. W. Holzmann
1. In 132 cockroaches the main leg nerve on one side (right), of the
metathoracic segment was crossed to the opposite (left) side and allowed to
regenerate. In 3-8 wk, 59% of the animals displayed reflex activity in the
left leg (behaviorally demonstrated by leg withdrawal following tarsal
stimulation). 2. EMGs from the femoral extensor revealed potentials
characteristic of normal activity in the extensor, which is innervated by
an identified motor neuron, Ds. 3. Intracellular recordings from processes
within the right hemiganglion of the metathoracic ganglion (CNS)
demonstrated 1:1 activity between a unit in the CNS recording and the EMG
of the left extensor. Subsequent intracellular staining revealed that the
unit was on the right side of the CNS and was identified as motor neuron Ds
by the location of its soma and dendrites. This finding indicated that
specific, contralateral, efferent reinnervation occurs in the cockroach. 4.
In normal cockroaches a monosynaptic reflex exists between hair plate
afferents and Ds. A temporal analysis (stimulus-interval histogram)
indicated that the reflex is also established in the crossed-regenerated
animals. These data suggested that specific contralateral afferent
reinnervation also occurs in the cockroach and that the monosynaptic nature
of the normal reflex was reestablished. 5. Therefore, cell-to-cell
specificity in neuron-to-neuron or neuron-to-muscle interactions not only
occurs in normally developing or regenerating animals but also occurs
between contralaterally homologous target cells, given the proper
experimental conditions. It is also suggested that this experimental
procedure of redesigning pathways may be a useful tool for further studies
of behavior.
