Metabolic changes in deafferented central neurons of an insect, Acheta domesticus. II. Effects on cholinergic binding sites and acetylcholinesterase

Abstract

Following the finding that cereal deafferentation of developing giant interneurons in the terminal abdominal ganglion (TG) of the cricket Ache& dome&us reduces TG protein metabolism within target interneuron dendrites and somata (Meyer and Edwards, 1982), it is now shown that deafferentation alters the turnover of three macromolecules associated with cholinergic transmission in the cereal sensory-giant interneuron pathway.The labeled specific ligands 3H-quinuclidinyl benzilate and 1251-cY-bungarotoxin were used to assay populations of putative TG muscarinic and nicotinic cholinergic receptors, respectively, in control and deafferented groups of ganglia. The AChE activity of TG was also determined by assay and histochemical methods.Long-term deafferentation sustained throughout postembryonic development markedly reduces the densities of both muscarinic and nicotinic binding sites in the TG, short-term deafferentation of adult TG also leads to characteristic alterations in the properties of all three choline@ markers within several days. Rapid changes seen in adults thus correlate with ultrastructural data demonstrating loss of afferent terminals within hours of sensory appendage removal.We propose that peripheral innervation-dependent regulatory mechanisms operate in both the developing and adult insect nervous system. Such mechanisms may influence transsynaptitally the synthesis and turnover of specilic macromolecules, some of which may reside on the cell surface of insect central neurons that are part of the cereal sensory-giant intemeuron system.

Immunological probes reveal spatial and developmental diversity in insect neuroglia

“…3, B, C) is not diminished after a located at the inner cortical rind margin, from which delicate majority of sensory axons and terminals have degenerated folcytoplasmic processes project into neuropil and ramify. Two lowing cereal deafferentation (Meyer et al, 1986). These results MAbs (3G6 and 8Bll) label neuropil in a pattern that suggests indicate that MAb 3G6 labels a glial, rather than a neuronal, Figure 4.…”

“…Slight displacement or loss of volume is apparent in deafferented neuropil, a consequence of the absence of substantial number of sensory axon terminals. Morphological evidence of degeneration of cereal sensory axon terminals in target neuropil has been shown to be present within less than 12 hr (Meyer et al, 1986); within 1 week, the vast majority of terminals will have degenerated. Comparison of 3G6 immunoreactivity in 15 d deafferented (B) and paired control (C) cereal sensory nerve demonstrates that 3G6 antigenicity remains in the denervated nerve stump, despite loss of majority of nerve fibers by this time.…”

“…A second set of MAbs was generated directly by immunization of BALB/c mice with an immunogen enriched for adult glial cell membranes derived from pooled deafferented cereal sensory nerve stumps. Denervated stumps were harvested from animals whose cereal appendages had been removed 15 d prior to preparation, a period judged sufficient to allow the vast majority of nerve fibers in the cereal nerve to degenerate (Meyer et al, 1986). The immunization regimen consisted of 1 primary injection of 100 pg glial enriched membranes in complete adjuvant, followed by 2 successive rounds of booster immunizations (with incomplete adjuvant) at 2 week intervals.…”