Ultrastructure of the ‘active zone’ in the frog neuromuscular junction

Dreyer, Florian; Peper, K.; Akert, K.; Sandri, C.; Moor, H.

doi:10.1016/0006-8993(73)90699-9

Cited by 213 publications

(87 citation statements)

References 8 publications

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“…Therefore, a subceilular organization appears to exist in which Ca 2+ channels are very close to the synaptic vesicles at the active zone (see Zucker and Stockbridge, 1983;Simon and Llinas, 1985;Zucker and Fogelson, 1986;Smith and Augustine, 1989). This is supported by ultrastructural observations (see Dreyer, 1973;Heuser et al, 1979;Pumplin et al, 1981) and fluorescent monitoring of Ca 2+ (see Smith and Augustine, 1988;Swandulla et al, 1991;Llinas et al, 1992). Furthermore, the highest density of presynaptic Ca 2+ channels is located directly opposite to the highest density of postsynaptic receptors (Robitaille et al, 1990).…”

Section: The Relationship Between Ca 2 + -Entry Intraterminal Ca 2 +mentioning

confidence: 77%

Presynaptic plasticity: The regulation of Ca2+-dependent transmitter release

Verhage

Ghijsen

Silva

1994

Progress in Neurobiology

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Section: The Relationship Between Ca 2 + -Entry Intraterminal Ca 2 +mentioning

confidence: 77%

Presynaptic plasticity: The regulation of Ca2+-dependent transmitter release

Verhage

Ghijsen

Silva

1994

Progress in Neurobiology

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“…2). The junctional folds are arranged as shallow grooves, 0'3-04 /im deep, perpendicular to the long axis of the muscle; the openings of the folds are quite widely spaced (0.5-0.8 ,um apart) and are opposite the putative release sites (Couteaux & Pecot-Dechavassine, 1974;Dreyer, Peper, Akert, Sandri & Moor, 1973). As in mammalian end-plates, the post-junctional membrane at the crest of the folds (i.e.…”

Section: Resultsmentioning

confidence: 99%

Distribution of acetylcholine receptors at frog neuromuscular junctions with a discussion of some physiological implications.

Matthews-Bellinger¹,

Salpeter²

1978

The Journal of Physiology

215

124

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SUMMARY1. The distribution of acetylcholine receptors (AChR) at frog cutaneous pectoris neuromuscular junctions was studied quantitatively using [125I]a-bungarotoxin (a-BTX) labelling and EM autoradiography.2. We found that, as in mouse end-plates, the AChR is localized uniformly along the thickened post-junctional membrane. In the frog muscle this specialized membrane constitutes approximately the top 50 % of the junctional folds.3. The receptor site density is 26,000 + 6000 sites/,um2 on the thickened postjunctional membrane and falls sharply to 50 sites/fum2 within 15 Itm from the axon terminal.4. a-BTX site density on the presynaptic axonal membrane was directly determined to be at most 5 % of the value on the thickened post-junctional membrane.5. The high post junctional AChR site density leads us to conclude that: (a) each quantum of ACh needs to spread only over a very small post-junctional area (to be called the 'critical area') before it encounters as many AChR (plus AChE) sites as there are ACh molecules in the quantum (for a packet of 104 ACh molecules this critical area is-03 #um2), (b) the average concentration of ACh prevailing in

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“…Photographs of each fractured endplate were taken and the active zones traced and measured with a bit pad (Sigma Scan, Jandel Scientific). An active zone was defined by the presence of two apposed rows of intramembranous particles (Dreyer et al, 1973;see Fig. 4B,D); three measurements were taken of each active zone and the mean used to define length.…”

Section: Active Zone Morphologymentioning

confidence: 99%

A sex difference in synaptic efficacy at the laryngeal neuromuscular junction of Xenopus laevis

1995

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Under physiological conditions, the response of Xenopus laevis laryngeal muscle fibers to nerve stimulation is sexually differentiated; subthreshold potentials are common in males and rare in females. This sex difference in muscle fiber response is correlated with sex differences in vocal behavior. Quantal analyses at male and female laryngeal synapses were performed to determine if there is a sex difference in synaptic strength. Quantal content at laryngeal synapses is significantly higher in females than in males. Values for quantal content in males can be increased by raising extracellular calcium concentration. There is no sex difference in miniature endplate potential amplitude suggesting that ACh receptor number or properties are not different in the sexes. Sex difference in synaptic strength thus appear presynaptic in origin; transmitter release is less in males. Ultrastructural analyses of the laryngeal motor terminal indicate that there is no sex difference in the length of active zones or in the number of channels per length of active zone. Thus, ultrastructural characteristics of the laryngeal motor terminal do not account for the pronounced sex difference in quantal content.

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Ultrastructure of the ‘active zone’ in the frog neuromuscular junction

Cited by 213 publications

References 8 publications

Presynaptic plasticity: The regulation of Ca2+-dependent transmitter release

Presynaptic plasticity: The regulation of Ca2+-dependent transmitter release

Distribution of acetylcholine receptors at frog neuromuscular junctions with a discussion of some physiological implications.

A sex difference in synaptic efficacy at the laryngeal neuromuscular junction of Xenopus laevis

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