Sprouting and nerve retraction in frog neuromuscular junction during ontogenesis and environmental changes

Jans, H.; Salzmann, R; Wernig, A.

doi:10.1016/0306-4522(86)90069-2

Cited by 40 publications

(16 citation statements)

References 35 publications

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“…Large frogs tended to have longer nerve terminals and larger muscle fibres than small frogs (Table 2), and the lengths of the fourteen nerve terminals measured in situ were correlated with the diameters of the muscle fibres they innervated; the equation of the regression line was: Ls = 6-1 + 5*4 D and its correlation coefficient, c.c., was 0-68. Similar results have been obtained by others (Kuno, Turkanis & Weakly, 1971;Jans et al 1986;Propst & Ko, 1987). The terminals on isolated muscle fibres were not included in this correlation since the diameters of those fibres may have been overestimated because the fibres were flattened (see Methods).…”

supporting

confidence: 72%

“…Frogs, R. pipiens, of either sex and ranging in weight from 13 to 68 g, were used in order to obtain a wide range of nerve terminal lengths (Jans, Salzmann & Wernig, 1986). The animals were anaesthetized by immersing them for 10-15 min in tap water with 1-2% ethyl-3-aminobenzoate (MS-222) (Aldrich Chem.…”

Section: Methodsmentioning

confidence: 99%

“…The results obtained from three additional junctions were rejected: two (from groups A and E) because they did not secrete rapidly when 4 mM-Mg2+ was applied, and one from group F because its cholinesterase reaction was spotty (Jans et al 1986). …”

Section: Methodsmentioning

confidence: 99%

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Correlation between quantal secretion and vesicle loss at the frog neuromuscular junction.

Hurlbut¹,

Iezzi²,

Fesce³

et al. 1990

The Journal of Physiology

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SUMMARY1. We measured the rate of occurrence of miniature endplate potentials (MEPPs) at identified endplates in frog cutaneus pectoris muscles treated with crude black widow spider venom (BWSV) or purified ac-latrotoxin (a-LTX) in calcium-free solutions, and we examined the relationship between the length of the nerve terminal and the total number of quanta secreted, and the relationship between the number of quanta secreted and the number of vesicles remaining at different times.2. The venom, or toxin, was applied in a modified Ringer solution with tetrodotoxin, 1 mM-EGTA and no divalent cations, and quantal secretion was started by applying Ca2+-free solutions with Mg2+. This was done to synchronize the quantal discharge at the various junctions in a muscle. Ringer solution was applied after the MEPP rate had declined to low levels, and then the muscle fibre was injected with Lucifer Yellow, the endplate stained for acetylcholinesterase and the length of the nerve terminal and the length of a sarcomere were measured on the fluorescent fibre.3. The total number of quanta secreted by a terminal was measured under a wide variety of experimental conditions: the weights of the frogs ranged from 13 to 68 g, the temperature from 9 to 28 0C, and the concentration of Mg2+ from 2 to 10 mM. In one series of experiments the Mg2+ was withdrawn after 3-4 min and reapplied 35-40 min later in order to divide the total output of quanta into two approximately equal bouts of secretion that were well separated in time.4. The total number of MEPPs recorded at a junction was loosely correlated with the length of its nerve terminal, but it was not affected by the temperature, the concentration of Mg2+ or the division of secretion into well-separated bouts of quantal release. The average total secretion per unit length was about 3700 quanta/sarcomere or about 1200 quanta/,#m.5. The average time course of quantal secretion per micrometre of terminal was determined at single junctions in muscles held at 22-23 0C or at 9-10 TC. Other muscles were fixed at various times during the course of secretion at each temperature and the number of synaptic vesicles remaining in cross-sections of the terminals were counted on electron micrographs. The number of vesicles remaining MS 7979 W. P. HURLBUT AND OTHERS per micrometre of terminal was determined from the number per cross-section and the section thickness.6. The average number of vesicles remaining per micrometre of terminal was negatively correlated with the average number of quanta secreted per micrometre; the slope of the regression line was -14 to -12 vesicles/quantum and its correlation coefficient was -0-91. It is concluded that a quantum of transmitter is derived from a single vesicle.

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confidence: 72%

Section: Methodsmentioning

confidence: 99%

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Correlation between quantal secretion and vesicle loss at the frog neuromuscular junction.

Hurlbut¹,

Iezzi²,

Fesce³

et al. 1990

The Journal of Physiology

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“…Endogenous adenosine, whether derived from secreted ATP or from some other source such as muscle, exerts an autoinhibitory effect by decreasing m. The alkylxanthines that block adenosine receptors, such as theophylline and 8-phenyltheophylline, enhance m (Ribeiro & Sebastiao, 1987). At amphibian neuromuscular synapses m is modulated by seasonal changes, decreasing in winter and increasing again in summer (Otsuka, Endo & Nonomura, 1962;Jans, Salzmann & Wernig, 1986). Seasonal adjustments in the amount of endogenous adenosine or its receptors found at these synapses may account for the seasonal change in m-, and this is examined in the present work.…”

Section: Introductionmentioning

confidence: 99%

Probabilistic secretion of quanta from nerve terminals in toad (Bufo marinus) muscle modulated by adenosine.

Bennett

Karunanithi

Lavidis

1991

The Journal of Physiology

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SUMMARY1. A study has been made of the effect of blocking endogenous adenosine on the statistics of quantal secretion at nerve terminals in toad (Bufo marinus) muscle, during summer and winter.2. Exogenous adenosine (10-50,M) reduces the mean quantal content of the endplate potential (EPP) recorded with an intracellular microelectrode (m) by 36 + 6 % (mean + S.E.M.), independent of the control value of m in both summer and winter. The variance of the EPP (S2) was reduced by adenosine in proportion to in-, so that the probability of quantal secretion (p) remained relatively constant.3. Exogenous adenosine reduces the mean quantal content of secretion recorded with an extracellular electrode (m-e) to a similar extent (47 + 6 %) at different relatively high secreting sites along nerve terminal branches in both summer and winter. 5. The variance of the EPP (S2) was always increased by theophylline to a greater extent than m-in summer, so that p decreased and Poisson rather than binomial statistics could be used to describe the distribution of EPP amplitudes. In winter, theophylline generally increased m and S2 to about the same extent, so that p did not change much.6. An autocorrelation analysis of the amplitude of successive EPPs in a long train at 0 5 Hz in high [Ca2+]o showed that these are likely to be independently distributed. Adenosine secreted by one impulse is then unlikely to affect secretion by a subsequent impulse in the train. 7. These observations are discussed in terms of the hypothesis that endogenously secreted adenosine at a release site inhibits secretion by nearby release sites in summer; this has the effect of reducing m-and to a greater extent S2 so that binomial rather than Poisson statistics can describe the frequency distribution of EPP amplitudes. MS 8527 M. R. BENNETT AND OTHERS

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“…Following elimination of some fibres, the remaining ones frequently increase their number of SYMPS~S. Many studies have revealed a size correlation between endplates and muscle fibres at all developmental stages (Anzenberger and Zenker, 1963;Raberger, 1971; Kordylewski, 1979;Jans et al, 1986). This phenomenon is interpreted as a functional tuning between the neuron and its target.…”

Section: Introductionmentioning

confidence: 99%

The Presynaptic Cell Determines the Number of Synapses in the Drosophila Optic Ganglia

Canal

Fariñas

Gho

et al. 1994

Eur J of Neuroscience

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The role of the pre- and postsynaptic cells in determining the number of synapses has been investigated in retina mosaics of the gigas (gig) mutant of Drosophila. Mutant photoreceptors are two to three times larger than those of the wild type, while adjacent cells in the mosaic retina and the lamina are normal in size. Serial electron microscope reconstructions of mosaic lamina cartridges show that gig photoreceptors establish more synapses upon lamina neurons than the normal photoreceptors do. By contrast, the number of feedback synapses that lamina neurons make onto gig photoreceptors does not increase. The increment in the number of synapses correlates positively with the increment of presynaptic cell membrane, resulting in constancy of synapse density. The phototactic response of flies bearing a gig eye is abnormal, indicating that the extra synapses are functional.

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Sprouting and nerve retraction in frog neuromuscular junction during ontogenesis and environmental changes

Cited by 40 publications

References 35 publications

Correlation between quantal secretion and vesicle loss at the frog neuromuscular junction.

Correlation between quantal secretion and vesicle loss at the frog neuromuscular junction.

Probabilistic secretion of quanta from nerve terminals in toad (Bufo marinus) muscle modulated by adenosine.

The Presynaptic Cell Determines the Number of Synapses in the Drosophila Optic Ganglia

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