ANTIBODIES RAISED AGAINST THE N-TERMINAL SEQUENCE OF DELTA-OPIOID RECEPTORS BLOCKED DELTA-MEDIATED SUPRASPINAL ANTINOCICEPTION IN MICE

A polyclonal antiserum directed against the first 16 aminoacids of the N-terminal sequence of the murine delta opioid receptor was raised in rabbits. The intracerebroventricular (i.c.v.) injection to mice of th e anti delta receptor IgGs impaired the antinociception produced by DP DPE, [D-Ala(2)]Deltorphin II, DADLE and beta-endorphin-(1-31) when stu died 24 h later in the tail-flick test. Antinociception produced by mo rphine and DAMGO was fully expressed in mice undergoing this treatment . The selective delta antagonist ICI 174864 (0.8 nmols/mouse, i.c.v.) significantly reduced the antinociceptive activity of opioids to the e xtent observed after giving the antibodies. ICI 174864 did not decreas e further the antinociception that remained after the anti delta recep tor serum. The specific binding displayed by 3 nM [H-3]-DPDPE was redu ced in membranes pre-incubated with the antiserum, whereas no change c ould be detected for 0.6 nM [H-3]-DAMGO labelling mu receptors. This e xperimental approach revealed the delta component of opioid-evoked sup raspinal antinociception in mice.