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Immunocytochemical localization of substance P receptor in rat periaqueductal gray matter: A light and electron microscopic study
Author(s) -
Barbaresi Paolo
Publication year - 1998
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19980907)398:4<473::aid-cne2>3.0.co;2-#
Subject(s) - neuropil , axon , biology , periaqueductal gray , population , excitatory postsynaptic potential , postsynaptic potential , neuroscience , dendrite (mathematics) , cell bodies , biophysics , anatomy , receptor , microbiology and biotechnology , central nervous system , biochemistry , midbrain , inhibitory postsynaptic potential , demography , geometry , mathematics , sociology
The distribution of substance P receptor (SP R ) protein in the rat periaqueductal gray matter (PAG) was investigated with a polyclonal antibody in the four subdivisions obtained by cytochrome‐oxidase histochemistry (Co‐hi). At light microscopic analysis, immunoreactivity appeared particularly dense in the dorsal subdivision of the PAG, was less intense in the other subdivisions, and formed several longitudinally organized columns. SP R ‐like immunoreactivity (SP R‐i ) was localized mostly to cell bodies and dendrites of small and medium‐sized neurons, which constituted about 6% of the total neuronal population of the PAG. At the electron microscopic level, SP R‐i could be observed on postsynaptic as well as on nonsynaptic regions of both cell bodies and dendrites. A small proportion of axons (4.2%) and axon terminals (5.3%) showed SP R‐i , the majority of labeled axon terminals, amounting to about 70% of synapsing elements, formed asymmetric synapses with dendrites. Rare astroglial processes displaying SP R‐i were also observed scattered throughout the neuropil of all PAG subdivisions. Our observations suggest that 1) also in the PAG, SP may act in a diffuse, nonsynaptic manner, probably on targets that are distant from its sites of release; and 2) SP may modulate excitatory neurotransmission acting presynaptically on those labeled axons that form asymmetric synapses. J. Comp. Neurol. 398:473–490, 1998. © 1998 Wiley‐Liss, Inc.