Target-dependent induction of functional neurotransmitter release in Helisoma neuromuscular cultures /
Identified buccal motoneuron 19 (B 19) of Helisoma acquired
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736580141&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Identified buccal motoneuron 19 (B 19) of Helisoma acquired secretary competence and synaptic potency following contact with its muscle targets in cell culture. Excitation-coupled neurosecretion was localized to neuritic sites of B 19 contact with appropriate muscle target following 48 hours of coculture. Muscle-contact also triggered a global elevation of spontaneous transmitter release in B 19. Contact between B 19 and inappropriate muscle targets failed to induce changes in secretary pro perties. Image analyses of neuronal architecture revealed that appropriate, but not novel, muscle targets elicited increased neuritic arborization at muscle- contact sites. The role of activity-dependent mechanisms in the induction of secretary properties in B 19 was investigated. Immediately prior to muscle contact, the sodium channel blocker, tetrodotoxin, or the acetylcholine receptor antagonist, d-tubocurarine chloride, was added to the medium. A 48 hour inhibition of TTX-sensitive presynaptic activity or curaresensitive postsynaptic activation blocked the induction of excitation-secretion coupling normally induced by appropriate target contact. In contrast to selective neuron B 19, secretary properties of buccal neuron 5 (B5), a neuron capable of forming novel chemical synapses with many inappropriate targets, did not require an activity-dependent induction of secretary properties prior to synapse formation. Induction of excitation-secretion coupling was dependent on postsynaptic membrane-bound signaling molecules. Vesicle recycling and neurotransmitter release assays demonstrated that postsynaptic phosphoinositol (PI)-linked proteins were required for induction of action potential-evoked secretion in B 19. The regulation of spontaneous release, however, was independent of PI-linked molecular determinants. Taken together, these findings suggest that neuron B 19 forms synaptic connections with its specific set of muscle targets through mechanisms involving target recognition and presynaptic induction. These mechanisms reside both in the muscle's ability to signal the neuron through surface proteins and the neuron's ability to recognize and transduce those retrograde signals into changes in presynaptic function. The process of synaptic induction continues with an activity-dependent signaling cascade that culminates in the acquisition of a secretary phenotype at synaptic sites of neuron B 19. |
|---|---|
| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | x, 120 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 105-116. |