Kappa opioid receptor immunoreactivity in the nucleus accumbens and caudate–putamen is primarily associated with synaptic vesicles in axons

• Published in: Neuroscience Vol. 96; no. 1; pp. 91 - 99
• Main Authors: Meshul, C.K., McGinty, J.F.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2000; Elsevier
• Subjects: Animals; Axons - metabolism; Biological and medical sciences; Caudate Nucleus - metabolism; Caudate Nucleus - ultrastructure; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; electron microscopy; Fundamental and applied biological sciences. Psychology; immunocytochemistry; Immunohistochemistry; kappa opioid receptor; Male; Microscopy, Electron; nucleus accumbens; Nucleus Accumbens - metabolism; Nucleus Accumbens - ultrastructure; opioid receptor; Putamen - metabolism; Putamen - ultrastructure; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, Opioid, kappa - metabolism; striatum; Synaptic Vesicles - metabolism; Synaptic Vesicles - ultrastructure; Vertebrates: nervous system and sense organs; BSA, bovine serum albumin; kappa opioid receptor; DAB, 3,3′-diaminobenzidine; immunocytochemistry; nucleus accumbens; TBS, Tris-buffered saline; NAs, nucleus accumbens shell; opioid receptor; KOR, kappa opioid receptor; PB, phosphate buffer; PBS, phosphate-buffered saline; striatum; electron microscopy; Rat; Immunocytochemistry; Rodentia; Central nervous system; Synaptic vesicle; Axon; κ Opioid receptor; Basal ganglion; Putamen; Nucleus accumbens; Vertebrata; Mammalia; Caudate nucleus; Brain (vertebrata)
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(99)90481-5

A rabbit polyclonal antiserum, raised against a C-terminal oligopeptide of the mouse kappa opioid receptor, was used to localize the cellular distribution of kappa receptors in the dorsal and ventral striatum of rats with light and electron microscopic immunocytochemistry. Prominent, diffuse kappa receptor immunoreactivity was present in the nucleus accumbens, particularly in the shell, ventral caudate–putamen and olfactory tubercle. The density of receptor immunoreactivity decreased in more dorsal areas of the caudate–putamen. In contrast, neuronal cell bodies stained clearly in the dorsal endopiriform nucleus, claustrum and layer VI of the adjacent cerebral cortex. Observations at the electron microscopic level in the dorsomedial shell of the nucleus accumbens and caudate–putamen revealed that the kappa receptor immunoreactivity was predominantly located in axons, often associated with synaptic vesicles, remote from the terminal or preterminal area. The few terminals which were labeled made slightly more asymmetrical than symmetrical contacts and the percentage of asymmetrical contacts observed was greater in the caudate than in the accumbens. A small number of postsynaptic spines was labeled; most of them were contacted by asymmetrical terminals. No labeling was observed in dendritic shafts. Thus, the predominant localization of kappa receptor immunoreactivity in axons is consistent with its role as a major inhibitor of glutamate and dopamine release in the dorsal and ventral striatum.