Relationship between neurokinin-1 receptor and substance P in the striatum: light and electron microscopic immunohistochemical study in the rat.
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.
Li
J L
JL
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Japan.
Wang
D
D
Kaneko
T
T
Shigemoto
R
R
Nomura
S
S
Mizuno
N
N
D000818:Animals; D003342:Corpus Striatum / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D051381:Rats / Q000378:metabolism*; D017208:Rats, Wistar; D018040:Receptors, Neurokinin-1 / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*
D018040:Receptors, Neurokinin-1; D013373:Substance P