L-Cysteinesulfinic acid is an endogenous neurotransmitter with agonistic effects on a variety of metabotropic glutamate receptors (mGluRs), including mGluR1, mGluR5, mGluR2, mGluR4, mGluR6, and mGluR8, with a pEC50 = 2.7 to 4.0. L- Cysteinesulfinic acid is a pld-coupled agonist of metabotropic excitatory amino acid (EAA) receptors.

mGluR4:2.7 (pEC50), mGluR1:3.92 (pEC50), mGluR6:4.0 (pEC50), mGluR2:3.9 (pEC50), mGluR5:4.6 (pEC50), mGluR8:3.94 (pEC50)

CHO cells expressing mGluR1, mGluR5, and mGluR8 were treated with L-Cysteinesulfinic acid (L-CSA) for 45 minutes at 37°C, and receptor activation was assessed by measuring [³H]-inositol phosphate accumulation. The results showed that L-CSA activated mGluR1 and mGluR5, inducing IP formation with lower potency than L-glutamate but with significant activity. In cells expressing mGluR2, mGluR4, and mGluR6, L-CSA inhibited forskolin-induced cAMP production, indicating activation of these Gi/o-coupled receptors via inhibition of adenylyl cyclase [1].