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Immunohistochemical characterization of substance P receptor (NK 1 R)‐expressing interneurons in the entorhinal cortex
Author(s) -
Wolansky Trish,
Pagliardini Silvia,
Greer John J.,
Dickson Clayton T.
Publication year - 2007
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/cne.21338
Subject(s) - parvalbumin , calretinin , entorhinal cortex , substance p , inhibitory postsynaptic potential , immunohistochemistry , calbindin , neurokinin a , neuropeptide , interneuron , neuropeptide y receptor , tachykinin receptor 1 , biology , somatostatin , aminobutyric acid , neuroscience , chemistry , medicine , receptor , hippocampus , immunology , biochemistry
It has been reported that application of substance P (SP) to the medial portion of the entorhinal cortex (EC) induces a powerful antiepileptic effect (Maubach et al. [1998] Neuroscience 83:1047–1062). This effect is presumably mediated via inhibitory interneurons expressing the neurokinin‐1 receptor (NK 1 R), but the existence of NK 1 R‐expressing inhibitory interneurons in the EC has not yet been reported. The present immunohistochemical study was performed in the rat to examine the existence and distribution of NK 1 R‐expressing neurons in the EC as well as any co‐expression of other neurotransmitters/neuromodulators known to be associated with inhibitory interneurons: γ‐aminobutyric acid (GABA), parvalbumin (PARV), calretinin (CT), calbindin (CB), somatostatin (SST), and neuropeptide Y (NPY). Our results indicated that NK 1 R‐positive neurons were distributed rather sparsely (especially in the medial EC), primarily in layers II, V, and VI. The results of our double‐immunohistochemical staining indicated that the vast majority of NK 1 R‐expressing neurons also expressed GABA, SST, and NPY. In addition, CT was co‐expressed in a weakly stained subgroup of NK 1 R‐expressing neurons, and CB was co‐expressed very rarely in the lateral EC, but not in the medial EC. In contrast, SP‐immunopositive axons with fine varicosities were distributed diffusely throughout all layers of the EC, appearing to radiate from the angular bundle. SP may be released in a paracrine manner to activate a group of NK 1 R‐expressing entorhinal neurons that co‐express GABA, SST, and NPY, exerting a profound inhibitory influence on synchronized network activity in the EC. J. Comp. Neurol. 502:427–441, 2007. © 2007 Wiley‐Liss, Inc.