Rat brain and heart muscarinic receptors: Modification with tetranitromethane

David Gurwitz*, Mordechai Sokolovsky

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Tetranitromethane at a concentration of 50 μM modifies the muscarinic receptors in membrane preparations from rat striatum, hippocampus and heart atrium, but not from the rat brain stem. While the binding of antagonists is only slightly altered, the modified receptor possesses an increased affinity of up to 8-fold for [3H]-acetylcholine binding to the high affinity state. This effect is absent if the nitration is carried out in the presence of an antagonist, but not in the presence of an agonist. The affinity for carbamylcholine is increased for both the high and the low affinity state of the receptor, as is evident from its ability to compete with a labeled antagonist. In addition, the proportion of binding sites (α) exhibiting the high affinity state for [3H]-acetylcholine or for carbamylcholine is increased upon nitration. This increase cannot be protected against by an antagonist, and is enhanced when nitration takes place in the presence of an agonist. With the agonists oxotremorine and [3H]-oxotremorine-M only the latter effect (i.e., increase in (α) is observed following nitration, while their dissociation constants for the receptor are unchanged. Data are discussed with respect to the proposed existence of subtypes of muscarinic receptors, as well as the importance of the agonist chosen for studies of ligand-receptor interactions.

Original languageEnglish
Pages (from-to)1124-1131
Number of pages8
JournalBiochemical and Biophysical Research Communications
Issue number3
StatePublished - 30 Sep 1985


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