Myotropic peptides. Orcokinin-3 is expressed throughout the central nervous system (at protein level). Orcokinin-3. Orcokinin-4. Belongs to the orcokinin family. Several N-terminally and/or C-terminally extended versions of the predicted orcokinin-1 sequence can be detected; it is unclear which one is the active form. Orcokinin-2 is only predicted. The gene model consists of only one exon and does not include an expected signal sequence.