I explored the relationship between neurite outgrowth and the onset of synaptic activity in the central neuropil of the leech embryo. In order to follow changes in early morphology and the onset of synaptic activity in the same identified neuron, whole cell patch clamp recordings and fluorescent dye fills were obtained from dorsal pressure-sensitive (P) cells, the first neurons that could be reliably identified in the early embryo. I followed the development of the P cell from the first extension of neurites to the elaboration of an adult-like arbour. Following the growth of primary neurites, we observed a profuse outgrowth of transient neurites within the neuropil that retracted to form spurs. Following a dormant period, stable secondary branches grew from the spurs and became tipped with terminals. At this time, neurites of the Retzius (R) cell, a known presynaptic partner in the adult, were observed to contact the terminals. Although voltage-dependent currents were seen in the P cell at the earliest stage, spontaneous synaptic activity was only observed when terminals had formed. Spontaneous release was observed before evoked release could be detected from the R cell. The results suggest that transient neurites are formed during an exploratory phase of development, whereas the more precisely timed outgrowth of stable neurites from the spurs signals functional differentiation during synaptogenesis. As spurs have also been observed in neurons of the mammalian brain, they may constitute a primordial synaptic organizer.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.20848 |
| Date | January 1998 |
| Creators | Reese, David R. |
| Contributors | Drapeau, Pierre (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001641648, proquestno: MQ44256, Theses scanned by UMI/ProQuest. |
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