These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: The "calcium antagonist" TMB-8 [3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester] is a potent, non-competitive, functional antagonist at diverse nicotinic acetylcholine receptor subtypes.
    Author: Bencherif M, Eisenhour CM, Prince RJ, Lippiello PM, Lukas RJ.
    Journal: J Pharmacol Exp Ther; 1995 Dec; 275(3):1418-26. PubMed ID: 8531111.
    Abstract:
    [3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester] (TMB-8) has seen wide use as an "intracellular Ca2+ antagonist." However, this study shows that TMB-8 acts as a noncompetitive, functional antagonist at diverse nicotinic acetylcholine receptor (nAChR) subtypes with potencies that exceed those for other reported effects of TMB-8, including inhibition of intracellular Ca2+ mobilization. TMB-8 is a potent inhibitor (IC50 approximately 400 nM) of agonist-stimulated ion flux mediated by functional human muscle nAChR or ganglionic alpha 3 beta 4-nAChR subtypes expressed by TE671/RD or SH-SY5Y cells. TMB-8 is also a potent inhibitor (IC50 approximately 500 nM) of a functional, central nervous system nAChR subtype that mediates nicotinic agonist-stimulated [3H]dopamine release from rat brain synaptosomes. TMB-8 is much less potent (IC50 approximately 30-200 microM) as an inhibitor of high-affinity 3H-labeled acetylcholine or 125I-labeled alpha-bungarotoxin binding to human muscle nAChR, ganglionic alpha 3 beta 4-nAChR, or ganglionic alpha 7-nAChR subtypes. Moreover, functional inhibition by TMB-8 of muscle-type nAChR is due to a reduction in agonist efficacy, but not potency, and is proportionately stronger with increasing agonist concentration, thereby suggesting that TMB-8 acts as a noncompetitive inhibitor. Similar effects are observed for local anesthetics such as tetracaine and procaine (functional IC50 values of approximately 5 and approximately 50 microM, respectively), although TMB-8 is the most potent of these agents. Studies with TMB-8 or BAPTA [1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid] analogues indicate that the amino group of TMB-8 is essential and that Ca2+ chelation is not required for inhibition of nAChR function.(ABSTRACT TRUNCATED AT 250 WORDS)
    [Abstract] [Full Text] [Related] [New Search]