Ultrastructural study of delta-opioid receptors in the dorsal horn of the rat spinal cord using monoclonal anti-idiotypic antibodies.
The ultrastructural localization of delta-opioid receptors was studied using monoclonal anti-idiotypic antibody prepared with an anti-D-Ala2-D-Leu5-enkephalin. Immunocytochemical techniques were used on vibratome sections from rats perfused with paraformaldehyde. A high density of immunoreactivity was observed in the dorsal horn of the spinal cord, particularly the two superficial layers, the dorsolateral funiculus and the area surrounding the central canal. The labelling was absent when the antibody was preincubated with the immunogen. Competition between the anti-idiotypic antibody and different ligands, delta or mu, was controlled by preincubation of tissue sections with the ligand in the presence of peptidase inhibitors for 3-4 h before addition of the anti-idiotypic antibody. Enkephalin, dermenkephalin and naltrindole induced disappearance of the labelling at 10(-9) M while dermorphin or dermorphin Lys7 were ineffective at the same concentration. Lamina II of the dorsal horn was studied by electron microscopy. The immunolabelling was mainly localized on cell membranes at appositions between the two neurons. About one third were localized between an axon terminal and a dendrite, the same proportion of labellings were between two axon terminals. Labelling was occasionally observed at appositions between a glomerular terminal and a dendrite or a terminal or at axoglial appositions. Axosomatic localizations were rare. The presynaptic localization of the labelling is in favor of a presynaptic mechanism of action for delta-opioids in the spinal cord, providing that these receptors are functional. delta-Opioid peptides probably act non-synaptically since receptors were never localized on synaptic differentiations.
Département de Neurobiologie des Signaux Intercellulaires, CNRS URA 1488, Université Pierre et Marie Curie, Paris, France.
F
F
Zerari
D
D
Zouaoui
M
M
Gastard
E
E
Apartis
J
J
Fischer
F
F
Herbrecht
A
A
Cupo
K
K
Cucumel
M
M
Conrath
D000818:Animals; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D051381:Rats; D017208:Rats, Wistar; D017465:Receptors, Opioid, delta / Q000032:analysis* / Q000648:ultrastructure; D013116:Spinal Cord / Q000737:chemistry*
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D017465:Receptors, Opioid, delta