L-Cysteinesulfinic acid (CSA) involvement in modulating periaqueductal gray (PAG) pressor neurons has been evaluated in the rat. Intra-PAG CSA induced an increase in mean blood pressure partially antagonized by (2S)-α-ethylglutamic acid (EGA), a group II metabotropic glutamate receptors (mGluRs) antagonist. Conversely, the NMDA antagonist, DL-AP5, or the mGluRs antagonists, (+)-MCPG, UPF523. or (RS)-α-methylserine-O-phosphate (MSOP), were devoid of any activity on the CSA effect. These data show that the excitatory amino acid CSA, probably by stimulating an mGluR, contributes with glutamate in modulating cardiovascular function at the PAG matter.