Abstract
Endogenous opioid peptides and opioid receptors form a neuromodulatory system, which plays an important part in the control of physiological pathways. In addition, some opioid peptides can function as endogenous messengers of the immune system and participate in the regulation of the immune response. The present studies indicated that mu, delta, and kappa opioid-like receptors were present in the gill and gonad of the scallop Chlamys farreri. Furthermore, the significance of opioid peptides involvement with the immune system is ascertained from the presence of mu, delta, and kappa opioid-like receptors on hemocytes of the scallop. Our report constitutes the first characterization of mu, delta, and kappa opioid-like receptors in the gill and gonad of the scallop Chlamys farreri.