Use this URL to cite or link to this record in EThOS:
Title: Structure, function and plasticity of convergent synapses in reinnervated muscle
Author: Costanzo, Ellen M.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
The experiments described in this thesis were directed towards clarifying the role of activity in sculpting patterns of innervation at adult reinnervated rat NMJs. Two hypotheses were tested: first, that activity is sufficient for synapse elimination, and second, that activity is necessary for synapse elimination. To test the first hypothesis, 4DL muscles were subjected to partial denervation and allowed to recover for at least 2 weeks from a period of paralysis. Polyneuronally innervated 4DL NMJs were examined to ask whether terminals contributing relatively small fractional occupancies of the endplate (<49% of total endplate area) were disproportionately weak and, in fact, in the process of being eliminated from endplates. Polyneuronally innervated endplates were identified with the vital dyes FM1-43 and RH414. Simultaneous intracellular recording and synaptic imaging were used to correlate input strength with size. To test the second hypothesis, 4DL muscles were subjected to partial denervation and paralysis, but were not allowed to recover from the activity block. Vital staining and immunocytochemistry revealed that competitive synapse elimination had taken place at some endplates, even when evoked and spontaneous activity was abolished throughout the muscles. These results show that activity, though influential, is neither sufficient nor necessary for the competitive elimination of synapses in reinnervated muscle. Thus, polyneuronal innervation may now be viewed as one of a number of stable states of innervation of skeletal muscle fibres. Further, the data suggest that the timing of transmitter-receptor activation is not the only mechanism by which inputs are removed during neuromuscular synapse elimination. Alternative mechanisms that may be operating during the competitive reinnervation of skeletal muscle will be discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available