Presence of Octopamine Receptors in Heart of the Bivalve Crassostrea viginica

Abstract

Octopamine (OA), a biogenic amine first identified in octopus, is well studied in arthropods and gastropods where it functions as a neurotransmitter and hormone. OA rarely has been reported in bivalves. Using HPLC we found OA in ganglia, gill, heart, palps and hemolymph of the oyster Crassostrea virginica and using immunohistofluorescence visualized OA in ganglia, gill and heart. Our physiological studies found OA is cardioactive for C. virginica and Mytilus edulis hearts. We hypothesize OA receptors are present in heart of C. virginica. To test this we did Western Blot (WB) using and pan TAAR (trace amine‐associated receptor) 1̊ antibodies, which are reactive with OA, beta‐phenylethylamine (b‐PEA), p‐tyramine (p‐TYR) and tryptamine receptors, but unresponsive to classical biogenic amines and histamine receptors. For WB, heart tissue lysate was prepared in NP‐40 detergent buffer containing protease inhibitor, followed by centrifuging to obtain supernatant with solubilized membrane proteins. Up to 30 µg of solubilized protein was subjected to SDS‐PAGE with 10% acrylamide gels and electroblotted onto nitrocellulose. Pan TAAR receptor immunoreactivity was revealed by 1̊ antibodies followed by HRP‐conjugated 2̊ antibodies. WB showed an 85 kD band corresponding to OA receptors in heart. The present project, coupled with our earlier studies, confirms the presence of OA receptors and furthers understanding of a physiological role for OA in C. virginica.