L-Cysteinesulfinic acid is an excitatory amino acid and agonist of metabotropic glutamate receptors (mGluRs).
1,2 It increases intracellular inositol phosphate levels in CHO cells expressing mGluR1, mGluR5, or mGluR8 (EC
50s = 120, 30, and 110 μM, respectively) and inhibits forskolin-induced cAMP production in CHO cells expressing mGluR2 or mGluR6 and hamster kidney cells expressing mGluR4 (EC
50s = 100, 100, and 2,000 μM, respectively).
2 It selectively binds to mGluR1α (K
i = 3,510 nM) over adrenergic, dopamine, histamine, muscarinic, nicotinic, or serotonin receptors (K
is = >10,000 nM for all). L-Cysteinesulfinic acid (1 mM) decreases mean arterial blood pressure and heart rate in rats when microinjected into the nucleus tractus solitarius (NTS).
1 L-Cysteinesulfinic acid can be formed
via oxidation of L-cysteine by reactive oxygen species (ROS), and conversion of cysteine to L-cysteinesulfinic acid in cysteine-containing peptide probes has been used to measure oxidative stress.
3 
