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Dissertation
Characterization of phosphoinositide-linked dopamine receptor
Doctor of Philosophy (Ph.D.), Allegheny University of the Health Sciences
May 1998
DOI:
https://doi.org/10.17918/00008427
Abstract
Evidence has accumulated suggesting that stimulation with dopamine or dopamine D1 agonists can activate phosphoinositide metabolism. Mechanisms underlying this phenomenon remain to be solved. Does the dopamine D1A receptor mediate the activation? Does dopamine interact with other receptors, which are known to link to phosphoinositide hydrolysis? Is phosphoinositide hydrolysis secondary to receptor-stimulated Ca²⁺ influx? What kind of G-protein subunits and phospholipase C isozymes are involved in the cascade? Clarification of these issues will help better our understanding of this novel dopamine system. With the aid of the dopamine D1A knockout animal model, the present study clearly excluded the involvement of this receptor in dopamine-induced phosphoinositide metabolism. It was found that when dopamine-mediated activation of adenylyl cyclase is blocked, dopamine or dopamine D1 agonist, SKF38393, stimulated inositol phosphates formation remains unchanged in this transgenic model. Difficulties have been only recently overcome with regard to using cell-free membrane preparations in studies of phosphoinositide metabolism. With this technique, it was demonstrated that aforementioned agonists possess the ability to stimulate the hydrolysis of exogenously provided phosphoinositide substrates. It was also shown that phosphoinositide formation in response to dopamine or SKF38393 was not mediated by the release of other neurotransmitters or by changes in intracellular Ca²⁺ level. Many efforts have been made to clone this novel dopamine receptor. One of factors that prevent this ambition becoming reality is the low abundance of this receptor in the brain. After screening of several cell lines, HN33.11 cell (a hybrid neuroblastoma x hippocampal neuron cell line) was found to duplicate most pharmacological features of dopamine-stimulated phosphoinositide hydrolysis in the brain. In this homogeneous cell population, dopamine or SKF38393 elicited inositol phosphate accumulation in a dose-dependent manner. This activation of phosphoinositide hydrolysis was specifically blocked by the dopamine D1 antagonist, SCH23390, but not by other receptor antagonists such as prazosin ([alpha]1-adrenoceptor), mesulergine (5-HT2/1C receptor), or atropine (muscarinic acetylcholine receptor). Extracellular calcium appeared to play little if any role in dopaminergic regulation of phosphoinositide metabolism. It was further demonstrated that Gq[alpha] subunit and phospholipase C [beta]3/[beta]4 relay the signals produced by stimulation of phosphoinositide-linked dopamine receptor in this cell line.
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Details
- Title
- Characterization of phosphoinositide-linked dopamine receptor
- Creators
- Li-Qing Jin
- Contributors
- Eitan Friedman (Advisor) - Drexel University, Allegheny University of the Health Sciences (1996-1998)
- Awarding Institution
- Allegheny University of the Health Sciences
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Allegheny University of the Health Sciences; Philadelphia, Pennsylvania
- Number of pages
- xiii, 150 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Pharmacology [Historical]; Allegheny University of the Health Sciences (1996-1998); School of Medicine (1996-1998)
- Other Identifier
- 991021888833404721