Cell and Tissue Research

, Volume 221, Issue 2, pp 303–310 | Cite as

Comparison of fast and slow synaptic terminals in lobster muscle

  • R. H. Hill
  • C. K. Govind


Synaptic terminals of fast (FCE) and slow (SCE) excitatory neurons were physiologically identified on separate fibres of one muscle, the closer muscle in lobster claws. The innervation by these identified fibers was demonstrated over long distances (7–21 μm) by examining serial thin sections at periodic intervals. The ultrastructure of each type of innervation was consistent both qualitatively and quantitatively in two separate samples. The FCE innervation is relatively simple in having consistently small-diameter terminals each forming a single long synapse, with few synaptic vesicles, and little if any postsynaptic apparatus. The SCE innervation is more complex in having larger-diameter but more variable terminals forming several short synapses, with many synaptic vesicles and an extensive postsynaptic apparatus. These differences in the size of the synapses and the number of synaptic vesicles parallel differences in transmitter release and fatigue sensitivity characteristic of the two types of innervation. The degree of elaboration of the postsynaptic apparatus may reflect differences in the amount of transmitter taken up after release. Our data reveal for the first time in a single muscle differences between FCE and SCE innervation previously reported in different muscles and in different species.

Key words

Neuromuscular terminal Fast synapse Slow synapse Lobster Ultrastructure 


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  1. Atwood HL (1976) Organization and neuromuscular physiology of crustacean neuromuscular systems. Prog Neurobiol 7:291–391Google Scholar
  2. Atwood HL, Jahromi SS (1978) Fast axon synapses of a crab leg muscle. J Neurobiol. 9:1–15Google Scholar
  3. Atwood HL, Johnston HS (1968) Neuromuscular synapses of a crab motor axon. J Exp Zool 167:457–470Google Scholar
  4. Atwood HL, Lang F, Morin WA (1972) Synaptic vesicles: Selective depletion in crayfish excitatory and inhibitory axons. Science 176:1353–1355Google Scholar
  5. Atwood HL, Govind CK, Jahromi SS (1977) Excitatory synapses of blue crab gastric mill muscles. Cell Tissue Res 177:145–158Google Scholar
  6. Costello WJ, Hill RH, Lang F (1981) Innervation patterns of fast and slow motoneurons during development of a lobster neuromuscular system. J Exp Biol 91:271–284Google Scholar
  7. Govind CK (1979) Distribution of multiterminal innervation in a muscle fiber of the lobster, Homarus americanus. Cell Tissue Res 199:171–175Google Scholar
  8. Govind CK, Chiang RG (1979) Correlation between presynaptic dense bars and transmitter output at lobster neuromuscular terminals by serial section electron microscopy. Brain Res 160:377–388Google Scholar
  9. Govind CK, Lang F (1974) Neuromuscular analysis of closing in the dimorphic claws of the lobster Homarus americanus. J Exp Zool 190:281–288Google Scholar
  10. Govind CK, Meiss DE (1979) Quantitative comparison of low- and high-output neuromuscular synapses from a motoneuron of the lobster (Homarus americanus). Cell Tissue Res 198:455–463Google Scholar
  11. Hill RH (1981) Innervation, neuromuscular function and ultrastructure of the closer muscle in the claws of the lobster, Homarus americanus. Ph. D. Thesis. Boston UniversityGoogle Scholar
  12. Jahromi SS, Atwood HL (1967) Ultrastructural features of crayfish phasic and tonic muscle fibers. Can J Zool 45:601–606Google Scholar
  13. Jahromi SS, Atwood HL (1974) Three-dimensional ultrastructure of the crayfish neuromuscular apparatus. J Cell Biol 63:599–613Google Scholar
  14. Lang F (1975) A simple culture system for juvenile lobsters. Aquaculture 6:389–393Google Scholar
  15. Mendelson T, Hoy RR, Salpeter MM (1980) Ultrastructure of neuromuscular junctions on a tonic and phasic crayfish muscle. Neuroscience Abstracts 6:179Google Scholar
  16. Thomas RC, Wilson VJ (1966) Marking single neurons by staining with intracellular recording microelectrodes. Science 141:1538–1539Google Scholar
  17. Tisdale D, Nakajima Y (1976) Fine structure of synaptic vesicles in two types of nerve terminals in crayfish stretch receptor organs: Influences of fixation methods. J Comp Neurol 165:369–386Google Scholar
  18. Wiersma CAG (1961) The neuromuscular system. In: Waterman TH (ed) The Physiology of Crustacea. Academic Press, New York, Vol II, pp 191–240Google Scholar

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • R. H. Hill
    • 1
    • 2
  • C. K. Govind
    • 1
    • 2
  1. 1.Boston University Marine Program, Marine Biological LaboratoryWoods HoleUSA
  2. 2.Scarborough College, University of TorontoWest HillCanada

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