Regeneration of cercal filiform hair sensory neurons in the first-instar cockroach restores escape behavior.
Neural regeneration in the escape circuit of the first-instar cockroach is described using behavioral analysis, electrophysiology, intracellular staining, and electron microscopy. Each of the two filiform hairs on each of the animal's cerci is innervated by a single sensory neuron, which specifically synapses with a set of giant interneurons (GIs) in the terminal ganglion. These trigger a directed escape run. Severing the sensory axons causes them to degenerate and perturbs escape behavior, which is restored to near normal after 4-6 days. Within this time, afferents regenerate and reestablish arborizations in the terminal ganglion. In most cases, regenerating afferents enter the cercal glomerulus and re-form most of the specific monosynaptic connections they acquired during embryogenesis, although their morphology deviates markedly from normal; these animals reestablish near normal escape behavior. In a few cases, regenerating afferents remain within the cercus or bypass the cercal glomerulus, and thereby fail to re-form synapses with GIs; these animals continue to exhibit perturbed escape behavior. We conclude that in most cases, specific synapses are reestablished and appropriate escape behavior is restored. This regeneration system therefore provides a tractable model for the establishment of synaptic specificity in a simple neuronal circuit.
Stern
M
M
Sussex Centre for Neuroscience, School of Biological Sciences, University of Sussex, Falmer, Brighton, U.K.
Ediger
V L
VL
Gibbon
C R
CR
Blagburn
J M
JM
Bacon
J P
JP
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004924:Escape Reaction / Q000502:physiology*; D017952:Ganglia, Invertebrate / Q000502:physiology*; D007814:Larva; D008465:Mechanoreceptors / Q000502:physiology*; D008854:Microscopy, Electron; D009416:Nerve Regeneration / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D010526:Periplaneta; D013569:Synapses / Q000502:physiology; D013623:Tail