Ultrastructure of synapses with different transmitter-releasing characteristics on motor axon terminals of a crab, Hyas areneas

  title={Ultrastructure of synapses with different transmitter-releasing characteristics on motor axon terminals of a crab, Hyas areneas},
  author={H. L. Atwood and Leo Marin},
  journal={Cell and Tissue Research},
SummarySynaptic terminals on branches of an excitatory motor axon in a spider crab (Hyas areneas) were examined by electron microscopy to determine whether differences in size, structure, and number of synapses could be correlated with differences in transmitter release. Terminals releasing relatively large amounts of transmitter during low frequencies of nerve impulses (“high-output” terminals) had larger synapses, more prominent presynaptic dense bodies (active zones), and fewer synapses per… 
Novel synaptic structures in the central nervous system of the locust Schlstocerca gregaria
An electron-microscopical study of locust thoracic ganglia reveals that synapses in the neuropily are morphologically heterogeneous, and there is a second type with a complex arrangement of presynaptic dense material and a non-dyadic postsynaptic configuration.
Morphological transformation of synaptic terminals of a phasic motoneuron by long-term tonic stimulation
It is concluded that the ongoing level of impulse activity can affect the ultrastructural differentiation of synaptic terminals and synapses of the phasic motoneuron.
Stimulation-induced changes at crayfish (Procambarus clarkii) neuromuscular terminals
Morphometric analysis of stimulated terminals revealed an increase in the number of dense bars and synaptic vesicles compared to their non-stimulated, contralateral counterparts, which indicates changes in their number provide a morphological basis for synaptic plasticity.
The Crustacean Synapse Scene at the End of the Millennium
The mechanism of the nerve impulse was first worked out in detail in the giant nerve axons of the squid and voltage-activated calcium channels first came to light in studies of crustacean muscle fibers.
Release probability of hippocampal glutamatergic terminals scales with the size of the active zone
It is demonstrated that the numbers of several active-zone proteins, including presynaptic calcium channels, as well as the number of docked vesicles and the release probability, scale linearly with the active- Zone area.
Ultrastructural analysis of low-threshold mechanoreceptive vibrissa afferent boutons in the cat trigeminal caudal nucleus
It is suggested that low-threshold mechanoreception conveyed through vibrissa afferents is processed in a bouton size-dependent manner in the Vc, which may contribute to the sensory-motor function of laminae III/IV in Vc.
Quantitative comparison of the structural features of slow and fast neuromuscular junctions in Manduca
  • M. B. Rheuben
  • Biology
    The Journal of neuroscience : the official journal of the Society for Neuroscience
  • 1985
The multiterminal slow and fast neuromuscular junctions of the moth Manduca sexta were compared using scanning, thin-section, and freeze- fracture techniques to see what structural features might
Analysis of evoked and spontaneous quantal release at high pressure in crustacean excitatory synapses
High pressure depressed evoked synaptic transmission by modulating the presynaptic quantal release parameters, but concomitantly enhanced spontaneousquantal release by an unknown mechanism.
Quantal Analysis Reveals a Functional Correlation between Presynaptic and Postsynaptic Efficacy in Excitatory Connections from Rat Neocortex
Recording from synaptically coupled pairs of pyramidal neurons in rat visual cortex suggested that during development of cortical connections presynaptic and postsynaptic strengths are dependently scaled.
Correlation of the Synaptic and Mechanical Properties of Two Slow Fibre Phenotypes in a Crustacean Muscle
It is shown that functional interpretations of muscle fibre properties require mechanical measurements on single muscle fibres to be related to their myofibrillar composition and that relatively few studies have established these relationships at the level of single, phenotypically identified Muscle fibres of crustaceans.


A hypothesis to account for the development of the neuromuscular apparatus is presented, in which it is suggested that production of new synapses is more important than enlargement of old ones as a mechanism for allowing the axon to adjust transmitter output to the functional needs of the muscle.
Correlated Electrophysiological and Ultrastructural Studies of a Crustacean Motor Unit
It is proposed that both nerve and muscle fiber properties may be determined by the developmental pattern of nerve growth as well as the development and physiological performance of the crustacean motor unit.
Nonhomogeneous excitatory synapses of a crab stomach muscle.
Evidence was obtained that not all synapses on a muscle fiber are equivalent, particularly evident at the morphological level in serially sectioned nerve terminals, and it is postulated that about half the morphologically identified synapses are relatively inactive.
Presynaptic dense bars at neuromuscular synapses of the lobster, Homarus americanus
The threedimensional ultrastructure of presynaptic dense bars was examined by serial section electron microscopy in the excitatory neuromuscular synapses of the accessory flexor muscle in the limbs of larval, juvenile, and adult lobsters, suggesting that the extrasynaptic bars denote early events in synapse formation.
Physiological regulation of synaptic effectiveness at frog neuromuscular junctions.
Nerve terminals in two different muscles of the frog, the sartorius and cutaneous pectoris, have been found to differ sharply in safety factor, and the greater release at c.p. junctions is likely to be due to a ‘physiological’ difference between the two populations of terminals.
Differentiation of identifiable lobster neuromuscular synapses during development
The ultrastructure of physiologically identified low and high release synapses arising from a single axon on fibres of the distal accessory flexor muscle (DAFM) in a mature lobster was examined by serial section electron microscopy to determine the point at which differentiation occurs during development.
Quantitative comparison of low- and high-output neuromuscular synapses from a motoneuron of the lobster (Homarus americanus)
A difference in dense body area parallels the difference in quantal content of synaptic transmission between the lowand high-output terminals and supports the hypothesis that presynaptic densities represent the ultrastructural correlates of transmitter mobilization and/or release.
Calcium and Facilitation at Two Classes of Crustacean Neuromuscular Synapses
The results suggest that the mechanism of synaptic facilitation is similar for both classes of synapses and occurs after the stage in transmitter release involving Ca++.
Comparative analysis of an excitatory motor unit in crustaceans
Selection of nerve terminals to muscle fibers appears to be a general rule of organization in the stretcher excitatory motor unit in decapod crustaceans, indicating that all muscle fibers in the motor unit are activated to approximately the same extent at the higher levels of activity.