Despite the wealth of data concerning the roles of α-CGRP in nociceptive behaviors, α-CGRP-null mice showed no obvious phenotypic differences in nociceptive behaviors from wild type. The present studies specifically demonstrate that α-CGRP null mice showed no CGRP immunoreactivity from the spinal cord, implying that CGRPs in the mice spinal cord are mainly a-isoforms. However, the nociceptive behaviors of the null mice are not significantly different from the wild type mice in thermal nociceptive behaviors on hotplate, chemical nociception tests to intraplantar capsaicin or formalin injection, and visceral pain behaviors to intraperitoneal acetic acid or magnesium sulfate injections. These data suggest that α-CGRP is dispensable for nociceptive behaviors or that compensatory mechanisms may exist to overcome the absence of this peptide.