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      Homoanatoxin: A potent analogue of anatoxin-a

      , , , , ,
      Biochemical Pharmacology
      Elsevier BV

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          Abstract

          The natural toxin anatoxin-a (AnTx) is a potent nicotinic agonist that is valuable for the study of nicotinic receptors. We have synthesized 2-(propan-1-oxo-1-yl)-9-azabicyclo[4.2.1]non-2-ene, the homologue of AnTx in which the side-chain is extended by one methylene unit from a methyl to an ethyl ketone. This chemistry would allow the generation of a tritiated product and the homologue, designated homoanatoxin (HomoAnTx), has been characterized here with that aim in mind. In competition binding assays at neuronal nicotinic ligand binding sites characterized by [3H]nicotine and [125I]-alpha bungarotoxin, HomoAnTx retained the same potency as the parent molecule, with Ki values of 7.5 nM and 1.1 microM, respectively. In contrast, it showed little inhibition of muscarinic binding defined by [3H]-quinuclidinyl benzilate. HomoAnTx is a potent nicotinic agonist in frog muscle contracture assays, having four times the potency of carbamylcholine and one tenth of the activity of AnTx itself. The N-methylated version of HomoAnTx was more than two orders of magnitude weaker in both functional and binding assays. The successful synthesis of HomoAnTx with retention of high nicotinic potency offers a route for the generation of novel, potent radiolabelled nicotinic ligands.

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          Author and article information

          Journal
          Biochemical Pharmacology
          Biochemical Pharmacology
          Elsevier BV
          00062952
          February 1992
          February 1992
          : 43
          : 3
          : 419-423
          Article
          10.1016/0006-2952(92)90558-Z
          1540199
          01ac20af-a227-4962-8103-68b3d161a361
          © 1992

          https://www.elsevier.com/tdm/userlicense/1.0/

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