Delta and kappa opioid receptors in eyestalk ganglia of a crustacean

Abstract

Crustacean eyestalk ganglia are part of the protocerebrum and have been demonstrated to produce numerous neurohormones. 3H(2- d-Pen, 5- d-Pen)-enkephalin, 3H-(—)-ethylketocyclazocine and 3H( d-Ala 2-NMePhe-Glyol 5)-enkephalin were used as ligands for opioid receptors on neuronal membrane preparations of eyestalk ganglia under consideration of their stereospecific binding properties. In context with saturation binding isotherms, association and dissociation plots, we demonstrate here two opioid receptors; a delta-type receptor with high affinity ( B max 68.5 fmol/mg protein, K d=4.0 nM) and low affinity ( B max 493 fmol/mg, K d = 83.6 nM) and a second receptor of kappa-type with B max of 3.1 pmol/mg protein and K d = 68.6 nM.