Development of Drosophila larval neuromuscular junctions: Maintaining synaptic strength

H. Li, X. Peng, R. L. Cooper

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


In spite of the available information about the development of Drosophila neuromuscular junctions, the correlation between nerve terminal morphology and maintenance of synaptic strength has still not been systematically addressed throughout larval development. We characterized the growth of the abdominal longitudinal muscle 6 (m6) and the motor terminals Ib and Is that innervate it within segment 4. In addition, we measured the evoked excitatory junction potential (EJP) amplitudes while the Ib and Is axons were selectively recruited. Regression analysis with natural log transformation of response variables indicated that the developmental curves for m6 and the motor axons Ib and Is were best fitted as second order polynomial regressions during larval development. Initially Is terminals are longer and possess more synaptic varicosities at the first instar stage. The Is terminals also grow faster in subsequent developmental stages. The growth of nerve terminals and their target m6 are not proportional although tightly correlated. This results in a larger average muscle area innervated by a single varicosity as the animal develops. The amplitudes of the EJPs of Ib and Is neurons show no developmental difference in their amplitudes from the first to the late third larval instar. The Is axon consistently produced larger EJPs than the Ib axon at each developmental stage. The time constants for both rising and decay phases of EJPs increase exponentially throughout larval development. The results presented not only help in quantifying the normal development of Drosophila neuromuscular junctions, but also provide a framework for future investigations to properly interpret developmental abnormalities that may occur in various mutants.

Original languageEnglish
Pages (from-to)505-513
Number of pages9
Issue number2
StatePublished - Dec 20 2002

Bibliographical note

Funding Information:
We thank Mr. Garrett Sparks (University of Kentucky) for editorial comments and Dr. Doug Harrison (University of Kentucky) for helping to maintain the fly stocks and training the authors on fly care and maintenance. Funding was provided in part by NSF Grants IBN-9808631 (R.L.C.) and NSF-ILI-DUE 9850907 for equipment (R.L.C.). This work fulfilled a part of the PhD requirements for H.L.


  • Neuromuscular junction
  • Neurotransmission
  • Synapse

ASJC Scopus subject areas

  • Neuroscience (all)


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