Relationship between neurokinin-1 receptor and substance P in the striatum: Light and electron microscopic immunohistochemical study in the rat

✍ Scribed by Li, Jin-Lian; Wang, Dan; Kaneko, Takeshi; Shigemoto, Ryuichi; Nomura, Sakashi; Mizuno, Noboru

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 627 KB
• Volume: 418
• Category: Article
• ISSN: 0021-9967
• DOI: 10.1002/(sici)1096-9861(20000306)418:2<156::aid-cne3>3.0.co;2-z

✦ Synopsis

The synaptic relationship between substance P (SP) and its receptor, i.e., neurokinin-1 receptor (NK1R), was examined in the striatum of the rat by confocal laser-scanning microscopy and electron microscopy. For confocal laser-scanning microscopy, triple-immunofluorescence histochemistry was performed to label NK1R, SP, and vesicular acetylcholine transporter (a specific marker for cholinergic neurons). In electron microscopic double-immunolabeling study, immunoreactivity for NK1R was detected with the silver-intensified gold method, while immunoreactivity for SP was detected with peroxidase immunohistochemistry. Simultaneous immunolabeling of NK1R and SP revealed significant mismatch at the synaptic level: although some SP-immunopositive axon terminals were in synaptic contact with NK1R-immunopositive sites of plasma membrane, NK1R-immunoreactivity was observed at both synaptic and non-synaptic sites of plasma membrane. Thus, SP released from the sites remote from NK1Rs might diffuse in the extracellular fluid to act, as a paracrine neurotransmitter, on NK1Rs distant from its releasing site. SP neurotransmission in the striatum might occur not only synaptically but also extrasynaptically. The SP-NK1R system might constitute an association system within the striatum.