PURPOSE:To investigate the subcutaneous injection of carbon dioxide (CO 2 ) on neuropeptides Calcitonin Gene-Related Peptide (CGRP) and Substance P (SP) secretion in rat skin. METHODS:Fifty-six Wistar-EPM rats were distributed in two groups: one for CGRP analysis, the other for SP analysis. Each group was subdivided into four subgroups: control (Cont), control with needle (ContNd), CO 2 injection (CO 2 Inj) and atmospheric air injection (AirInj) -with seven animals each. Sample analyses of partial skin were conducted by Western Blotting (WB). RESULTS:In SP group, there was a decrease in the amount of neuropeptides in subgroups CO 2 Inj and AirInj. Similarly, in CGRP group, there was a decrease in the amount of pro-CGRP neuropeptides (15 kDa) in subgroups CO 2 Inj and AirInj; Nevertheless, there was no decrease in the amount of CGRP (5 kDa) in any subgroups.CONCLUSION: Subcutaneous injection of CO 2 and atmospheric air decreased the amount of Substance P and pro-Calcitonin GeneRelated Peptide (15 kDa) neuropeptides in rat skin.