Details

Autor(en) / Beteiligte

• Role, Lorna W.
• Roufa, Dikla G.
• Fischbach, Gerald D.

Titel

The Distribution of Acetylcholine Receptor Clusters and Sites of Transmitter Release along Chick Ciliary Ganglion Neurite-Myotube Contacts in Culture

Ist Teil von

• The Journal of cell biology, 1987-02, Vol.104 (2), p.371-379

Ort / Verlag

New York, NY: Rockefeller University Press

Erscheinungsjahr

1987

Quelle

MEDLINE

Beschreibungen/Notizen

• 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 μm of a nerve process or 10 μm of the base of a growth cone was considered to be a neurite-associated 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 ∼6 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 μm 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.