The compound 2-(4-phenylpiperidino)cyclohexanol (AH5183), a potent inhibitor of vesicular acetylcholine (ACh) uptake, blocks the nerve impulse stimulated release of ACh from the superior cervical ganglion of the cat in a use dependent manner, but not until 14% of the initial ganglial ACh content has been released. The first objective of this work was to determine if blockade of ACh release was associated with a depletion of vesicular ACh. By using black widow spider venom (BWSV), a secretagogue which induces vesicular exocytosis, it was shown that depletion of vesicular stores did not likely occur as a result of AH5183 blockade. Furthermore, labeling the ACh synthesized in the presence of the drug, revealed that labeled ACh and pre-existing ACh were equally well released by the venom suggesting that some vesicles were insensitive to AD5183. / Thus, the second objective of these studies was to test whether an AH5183-insensitive vesicular compartment existed and to investigate which subcellular compartments played a role in the release of ACh by the various stimuli. Rat hippocampal slices were stimulated with K$ sp+$, in the presence or absence of AH5183, and then with the purified active toxin of BWSV, $ alpha$-LTX. The toxin's main effect was to decrease the ACh content of the cytoplasm. Labeling the ACh synthesized in the presence of AH5183 demonstrated that stimulation increased with specific activity of the ACh stored by the denser vesicular compartment, normally associated with a high turnover of transmitter, but not that of the lighter vesicles associated with a storage function. / To investigate how the occluded compartments recovered form AH 5183, hippocampal slices were drug-exposed, stimulated, and allowed to recover in the drug's absence. ACh synthesized during the recovery was labeled. Transmitter release and the ACh content of the occluded compartments recovered slowly from the effects of AH5183 and no quantitative relationship was found between the two events. The denser vesicular compartment recovered 1.5 times as quickly as the lighter one. The denser compartment accumulated labeled ACh while the lighter did not, suggesting that different sources of ACh exist within the cytoplasm.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.74609 |
| Date | January 1991 |
| Creators | Cabeza, Rafael de Jesus |
| 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 | Doctor of Philosophy (Department of Pharmacology and Therapeutics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001215086, proquestno: AAINN67624, Theses scanned by UMI/ProQuest. |
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