Gardner, B.R. and Hall, D.A. and Strange, P.G. (1997) Agonist action at D-2(short) dopamine receptors determined in ligand binding and functional assays. Journal of Neurochemistry, 69 (6). pp. 2589-2598. ISSN 0022-3042.
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Mechanisms of agonist action at the G protein-coupled D-2(short) dopamine receptor expressed in Chinese hamster ovary cells have been investigated. Agonist binding was assayed in the presence and absence of GTP (100 mu M). Data in the absence of GTP were fitted best by a two-site model (apomorphine, dopamine, 10,11-dihydroxy-N-n-propylnorapomorphine hydrochloride, and quinpirole) or a one-site model [bromocriptine, dihydroergocristine, and (-)-3-(3-hydroxyphenyl)-N-propylpiper idine hydrochloride], whereas in the presence of GTP a one-site model was the best fit for all compounds. Agonist binding parameters were used to provide a measure of the ability of the agonist to stabilise the ternary complex of agonist/receptor/G protein. Agonist stimulation of [S-35]guanosine 5'-O-(3-thiotriphosphate) ([S-35]GTP gamma S) binding for a range of agonist concentrations was measured and the EC50 and maximal effects determined. The initial rates of [S-35]GTP gamma S binding induced by maximally stimulating agonist concentrations were also recorded. Simultaneous inhibition of agonist-stimulated [S-35]GTP gamma S binding and receptor occupancy by spiperone was determined. Agonist inhibition of forskolin-stimulated cyclic AMP accumulation was determined for a range of agonist concentrations and the EC50 and maximal inhibition recorded. The data on the maximal agonist responses showed that it was possible to detect a spectrum of agonist efficacy (partial and full agonism) in both functional assays. The data on the apparent potencies of agonists to elicit the functional responses showed that different extents of amplification of response were seen for different agonists in both assays, The maximal activity data have been compared with the stabilisation of the agonist/receptor/G protein ternary complex as measured in binding assays.
|Uncontrolled keywords:||dopamine D-2 receptor; agonist action; ligand binding; [S-35]guanosine 5'-O-(3-thiotriphosphate) binding; cyclic AMP accumulation; G protein; ternary complex|
Q Science > QP Physiology (Living systems) > QP517 Biochemistry
|Divisions:||Faculties > Science Technology and Medical Studies > School of Biosciences|
|Depositing User:||M.A. Ziai|
|Date Deposited:||06 Mar 1914 14:56|
|Last Modified:||06 Mar 1914 14:56|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/18065 (The current URI for this page, for reference purposes)|
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