Localization of acetylcholine receptors and synaptic ultrastructure at nerve-muscle contacts in culture: dependence on nerve type

Cohen, Maxime C.; Weldon, P.R.

doi:10.1083/jcb.86.2.388

Cited by 87 publications

(39 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, muscle cells contacted by incompetent neurons, unlike those contacted by competent neurons, exhibited AChR patches elsewhere on their surface similar to those that normally occur on noncontacted muscle cells. It is therefore apparent that incompetent neurons derived from embryonic spinal cord, like those from other sources (Cohen and Weldon, 1980) have little influence on the distribution of AChRs. The fact that incompetent neurons develop SVAPs is also in agreement with previous electron microscopic observations of clusters of synaptic vesicles along the neurites of incompetent neurons (Cohen and Weldon, 1980).…”

Section: Discussionmentioning

confidence: 99%

“…It is therefore apparent that incompetent neurons derived from embryonic spinal cord, like those from other sources (Cohen and Weldon, 1980) have little influence on the distribution of AChRs. The fact that incompetent neurons develop SVAPs is also in agreement with previous electron microscopic observations of clusters of synaptic vesicles along the neurites of incompetent neurons (Cohen and Weldon, 1980). Clearly, the presence of synaptic vesicles per se does not provide an index of the competency of a neuron to influence AChR distribution in muscle.…”

Section: Discussionmentioning

confidence: 99%

“…As a result, AChRs become localized preferentially at sites of innervation, thereby permitting efficient synaptic transmission. Incompetent neurons, such as those of dorsal root ganglia and other noncholinergic neurons, are ineffective in this regard, thereby emphasizing the neural specificity of the triggering interaction (Cohen and Weldon, 1980;Role et al, 1985). The neural agent(s) that initiates these remarkable changes in AChR distribution has not yet been identified, but it is known that it can act in the absence of activation of AChRs, as well as in the absence of muscle and neuronal action potentials Rubin et al, 1980;Davey and Cohen, 1986).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Distribution of synaptic specializations along isolated motor units formed in Xenopus nerve-muscle cultures

Cohen¹,

Rodriguez-Marin²,

Wilson³

1987

J. Neurosci.

Self Cite

View full text Add to dashboard Cite

The capacity of individual muscle cells and neurons to establish synaptic specializations along the entire extent of their neurite- muscle contacts was assessed in culture. Spinal cord neurons derived from embryos of Xenopus laevis were plated at low density in cultures of Xenopus myotomal muscle cells in order to obtain isolated motor units whose neuron and muscle cells were not contacted by any other neuron. These isolated motor units were examined for localization of acetylcholine receptors (AChRs) after staining with fluorescent alpha- bungarotoxin and, in some cases, for localization of a synaptic vesicle antigen by immunofluorescence. The neurite-muscle contacts formed by competent neurons exhibited discontinuous sites of AChR localization occupying about 25% of the contact length as compared with 2% for incompetent neurons. Competent neurons, unlike incompetent ones, established these neurite-associated receptor patches (NARPs) on virtually all the muscle cells they contacted and functionally innervated them. These and other observations on the distribution of NARPs throughout the isolated motor units indicate that the capacity of competent neurons to establish NARPs extends to the limits of growth of most if not all of their neurites, that this capacity is least in the most proximal portions of initial neuritic segments, and that the overall capacity of muscle cells to generate NARPs can be saturated by long lengths of neurite-muscle contact. The results also suggest that even in the absence of competitive interactions between neurons there are spatial discontinuities in neuritic action and/or muscle response during the establishment of NARPs. Synaptic vesicle antigen patches (SVAPs) occurred along the neuritic arbor of all neurons, but their distribution in competent neurons (those which established NARPs) and in incompetent ones differed. For competent neurons the percentage of neurite length occupied by SVAPs was 4.8-fold greater on muscle cells than off, whereas the corresponding value for incompetent neurons was only 1.5-fold. This large preferential localization of SVAPs along neurite-muscle contacts of competent neurons was further associated with a colocalization of SVAPs and NARPs that was greater than predicted by chance. These results suggest that muscle cells are much more effective in influencing the distribution of synaptic vesicles along the neuritic arbor of competent neurons than along the arbor of incompetent neurons and that this influence is greatest at sites of postsynaptic differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Distribution of synaptic specializations along isolated motor units formed in Xenopus nerve-muscle cultures

Cohen¹,

Rodriguez-Marin²,

Wilson³

1987

J. Neurosci.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Within hours of contact, they resemble mature cholinergic synapses in many respects. They exhibit spontaneous release, high quantal content-evoked release, membrane thickenings, clouds of vesicles, and postsynaptic aggregation of ACh receptors (Anderson et al, 1977;Weldon and Cohen, 1979;Cohen and Weldon, 1980;Kidokoro et al, 1980;Kidokoro and Yeh, 1982;Brehm et al, 1984;Takahashi et al, 1987;Buchanan et al, 1989;Evers et al, 1989).…”

Section: Methodsmentioning

confidence: 99%

Direct Measurements of Presynaptic Calcium and Calcium-Activated Potassium Currents Regulating Neurotransmitter Release at CulturedXenopusNerve–Muscle Synapses

et al. 1997

View full text Add to dashboard Cite

The understanding of neurotransmitter release at vertebrate synapses has been hampered by the paucity of preparations in which presynaptic ionic currents and postsynaptic responses can be monitored directly. We used cultured embryonic Xenopus neuromuscular junctions and simultaneous pre-and postsynaptic patch-clamp current-recording procedures to identify the major presynaptic conductances underlying the initiation of neurotransmitter release.Step depolarizations and action potential waveforms elicited Na and K currents along with Ca and Ca-activated K (K Ca ) currents. The onset of K Ca current preceded the peak of the action potential. The predominantly -CgTX GVIA-sensitive Ca current occurred primarily during the falling phase, but there was also significant Ca 2ϩ entry during the rising phase of the action potential. The postsynaptic current began a mean of 0.7 msec after the time of maximum rate of rise of the Ca current. -CgTX also blocked K Ca currents and transmitter release during an action potential, suggesting that Ca and K Ca channels are colocalized at presynaptic active zones. In double-ramp voltage-clamp experiments, K Ca channel activation is enhanced during the second ramp. The 1 msec time constant of decay of enhancement with increasing interpulse interval may reflect the time course of either the deactivation of K Ca channels or the diffusion/removal of Ca 2ϩ from sites of neurotransmitter release after an action potential. Key word: neuromuscular junction; nerve terminal; calcium channel; charybdotoxin; conotoxin; synaptic delayNeurotransmitter release from nerve terminals is triggered by the entry of Ca 2ϩ through voltage-gated Ca channels (Katz, 1969;Augustine et al., 1987). Our understanding of the relationship between the presynaptic ionic currents and release is based largely on studies of the squid giant synapse (Katz and Miledi, 1967;Llinás et al., 1981;Charlton et al., 1982; Augustine et al., 1985a,b). Several critical questions remain, however, that one would like to address with equivalent biophysical rigor at a vertebrate synapse in which the presynaptic ionic currents and postsynaptic currents can be measured simultaneously and release can be resolved at the single quantum level. In this report we take advantage of a neuromuscular synapse preparation in which this can be done.Among the important pending questions are the timing and delay between Ca 2ϩ entry during an action potential and release, the roles of different Ca and Ca-activated K (K Ca ) channels in the release process, and the quantitative relationship between Ca 2ϩ influx and release. In squid, it has been shown that Ca 2ϩ enters principally during the repolarization phase of the action potential (Llinás et al., 1982). Physiological studies of various excitable secretory cells have shown that different types of Ca channels play a dominant role in triggering release in different terminals, and often multiple Ca channel types are present in any given terminal (Kerr and Yoshikami, 1984;Pfrieger et al., 1992, Luebke et al...

show abstract

“…Several lines of evidence suggest that NARPs mark sites of synapse formation in chick and Xenopus cultures. They are present on innervated muscle cells Fischbach and Cohen, 1973;Frank and Fischbach, 1979), and they are apparently uniquely associated with neurites of cholinergic neurons (Cohen and Weldon, 1980;Role et al, 1985). In Xenopus cultures, the amplitude and frequency of mepps are correlated with the extent of receptor accumulation (Anderson et al, 1979).…”

mentioning

confidence: 99%

The distribution of acetylcholine receptor clusters and sites of transmitter release along chick ciliary ganglion neurite-myotube contacts in culture.

Role¹,

Roufa²,

Fischbach³

1987

The Journal of Cell Biology

View full text Add to dashboard Cite

Abstract. Acetylcholine receptors accumulate along the length of cholinergic neuron-skeletal muscle contacts in vitro. The main purpose of this study was to describe, in a quantitative way, the distribution of acetylcholine receptor clusters induced by ciliary ganglion neurons over a period of time extending from hours to weeks after contacts are established. Neurites were filled with Lucifer Yellow and receptor clusters were identified with rhodamine-bungarotoxin. A cluster located within 5 gm of a nerve process or I0 l~m of the base of a growth cone was considered to be a neuriteassociated receptor patch (NARP). The first synaptic potentials were evoked 20 min after growth cone-myotube contact, and, after 24 h of co-culture, >60% of the nerve-muscle pairs tested were functionally connected. NARPs appear rapidly; the first clusters were detected "o6 h after the neurons were plated. They were composed of several small subclusters or speckles of rhodamine-bungarotoxin fluorescence. The initial accumulation of receptors may occur at the advancing tips of nerve processes because NARPs were found at >80 % of the growth cone-muscle contacts examined between 12 and 24 h of co-culture. Over the 3-wk period examined, the mean incidence of NARPs ranged between 1.0 and 2.6 per 100 gm of neurite-myotube contact, with the peak observed on the second day of co-culture. During the first 3 d in culture, when the neurons were multipolar, nearly all of the primary processes induced one or more clusters. With time, as the neurons become unipolar (Role and Fischbach, 1987) NARPs persisted along the remaining dominant process. Measurements made during the third day of co-culture suggest that NARPs disappear along shorter neurites before they retract. Synaptic currents were detected by focal extracellular recording at 55 % of the NARPs. The fact that spontaneous or evoked responses were not recorded at 45 % suggests that contacts with clusters exhibit two functional states. Two types of presynaptic specialization at identified NARPs observed by scanning electron microscopy appear to be correlated with the functional state.MBRYONIC motoneurons promote the accumulation of acetylcholine (ACh) I receptors (AChRs) at newly formed nerve-muscle junctions in vivo and in vitro Cohen, 1980;Steinbach and Bloch, 1986;Schuetze and Role, 1987). In chick cultures, it is clear that receptors accumulate soon after nerve-muscle contact is established, and that each neuron is capable of inducing more than one receptor cluster (Frank and Fischbach, 1979;Role et al., 1985). However, little information is available 1. Abbreviations used in this paper: ACh, acetylcholine; AChR, acetylcholine receptor; NARP(s), neurite-associated receptor patch(es); R-BTX, rhodamine-conjugated alpha-bungarotoxin.Portions of this work have appeared in abstract form (1982. Soc. Neurosci.

show abstract

Localization of acetylcholine receptors and synaptic ultrastructure at nerve-muscle contacts in culture: dependence on nerve type

Cited by 87 publications

References 59 publications

Distribution of synaptic specializations along isolated motor units formed in Xenopus nerve-muscle cultures

Distribution of synaptic specializations along isolated motor units formed in Xenopus nerve-muscle cultures

Direct Measurements of Presynaptic Calcium and Calcium-Activated Potassium Currents Regulating Neurotransmitter Release at CulturedXenopusNerve–Muscle Synapses

The distribution of acetylcholine receptor clusters and sites of transmitter release along chick ciliary ganglion neurite-myotube contacts in culture.

Contact Info

Product

Resources

About