Regeneration in the auditory system of nymphal and adult bush crickets Tettigonia viridissima

Abstract

Regeneration and reestablishment of synaptic connections is an important topic in neurobiological research. In the present study, the regeneration of auditory afferents and the accompanying effects in the central nervous system are investigated in nymphs and adults of the bush cricket Tettigonia viridissima L. (Orthoptera: Tettigoniidae). In all animals in which the tympanal nerve is crushed, neuronal tracing shows a regrowth of the afferents into the prothoracic ganglion. This regeneration is seen in both adult and nymphal stages and starts 10–15 days after nerve crushing. Physiological recordings from the leg nerve indicate a recovery of tympanal fibres and a formation of functional connections to interneurones in the same time range. Electrophysiological recordings from the neck connective suggest additional contralateral sprouting of interneurones and the formation of aberrant connections. The regeneration processes of the tympanal nerve in nymphal stages and adults appear to be similar.

Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket Gryllus bimaculatus

“…In situations where the deafferented interneurons do not have pre-existing contact with contralateral afferents, injury compensation requires more dramatic morphological change. Contralateral sensory sprouting across the midline following auditory deafferentation has been described in several cricket species as well as the locust, Locusta migratoria (Pallas and Hoy, 1986; Lakes et al, 1990; Krüger et al, 2011a,b). Limited quantitative measurements of L. migratoria contralateral afferent sprouting indicate that the N5 sprouting that we measured in G. bimaculatus , although perhaps somewhat more extensive than that seen in the locust, does not appear to be atypical for axonal growth in the insect system (Lakes et al, 1990).…”

“…Limited quantitative measurements of L. migratoria contralateral afferent sprouting indicate that the N5 sprouting that we measured in G. bimaculatus , although perhaps somewhat more extensive than that seen in the locust, does not appear to be atypical for axonal growth in the insect system (Lakes et al, 1990). After unilateral sensory ablation, input from sensory afferents on the intact side is necessary for dendritic sprouting and compensation in a number of insect systems and is required after deafferentation in the cricket (Murphey and Levine, 1980; Pallas and Hoy, 1986; Volman, 1989; Krüger et al, 2011b). However, it is not clear how deafferented dendrites and contralateral axons are stimulated to grow after deafferentation or whether axons and dendrites signal one another during the growth process.…”

“…However, additional studies have failed to detect large-scale reorganization of cortical dendrites after visual deprivation (Hofer et al, 2008) or even after direct retinal damage (Keck et al, 2008) in the adult. Physical injury to neurons via axotomy can lead to varying amounts of dendritic and axonal growth as well as shifts in dendritic arbor organization, as is seen in mouse superior cervical ganglion cells (Yawo, 1987), lamprey central neurons (Hall and Cohen, 1983), feline neck motor neuron (Rose et al, 2001), cricket terminal ganglion interneurons (Chiba et al, 1988; Chiba and Murphey, 1991), and in the cricket and locust auditory systems (Pallas and Hoy, 1986; Lakes and Kalmring, 1991; Krüger et al, 2011b). Deafferentation-induced elevator motor neuron sprouting in the metathoracic ganglion of locusts helps these animals recover proper wing patterns after unilateral tegula removal (Büschges et al, 1992; Wolf and Büschges, 1997).…”

“…However, only a handful of examples of such plasticity in the CNS in either adult vertebrates or invertebrates have been described, mainly in a few different species or in particular injury scenarios (Murphey et al, 1975; Bulloch and Ridgway, 1989; Büschges et al, 1992; Wolf and Büschges, 1997; Krüger et al, 2011b; Tavosanis, 2012). One of the more striking, positive, compensatory responses to injury has been described in the auditory systems of several species of field crickets (Hoy et al, 1985; Schildberger et al, 1986; Brodfuehrer and Hoy, 1988).…”

“…Deafferentation-induced elevator motor neuron sprouting in the metathoracic ganglion of locusts helps these animals recover proper wing patterns after unilateral tegula removal (Büschges et al, 1992; Wolf and Büschges, 1997). Within the cricket, deafferentation-induced compensatory dendritic responses have been demonstrated in both the terminal ganglion and the prothoracic ganglion (Murphey et al, 1975; Murphey and Levine, 1980; Hoy et al, 1985; Pallas and Hoy, 1986; Schildberger et al, 1986; Brodfuehrer and Hoy, 1988; Schmitz, 1989; Kanou et al, 2004; Horch et al, 2011; Krüger et al, 2011a,b). The deafferentation-induced compensation in the terminal ganglion consists mainly of changes in the strength of existing synapses (Murphey and Levine, 1980), though some dendritic sprouting has been noted (Murphey et al, 1975).…”