Morphological and chemical characteristics of substance P receptor-immunoreactive neurons in the rat neocortex.
Substance P receptor-expressing neurons in the rat cerebral neocortex were examined by single- and double-immunolabeling methods with an affinity-purified specific antibody to substance P receptor. Substance P receptor immunoreactivity was observed exclusively in non-pyramidal neurons. About a quarter of these substance P receptor-positive neocortical neurons showed intense immunoreactivity, and the other three quarters displayed weak substance P receptor immunoreactivity. The neurons showing intense substance P receptor immunoreactivity were large multipolar cells with a few long aspiny or sparsely-spiny dendrites, and were scattered throughout the neocortical layers except for layer I, and also in the underlying white matter. The weakly immunoreactive neurons were medium-sized multipolar cells with oval to round somata and aspiny varicose dendrites, and were distributed in all cortical layers with a bias to layers II-III and the superficial part of layer V. The double-immunofluorescence study revealed that almost all substance P receptor-positive neurons were immunoreactive for GABA, but negative for glutaminase. Substance P receptor immunoreactivity in GABAergic neocortical neurons were further examined by the double-immunofluorescence method with antibodies to markers for subgroups of GABAergic neurons. Somatostatin immunoreactivity was found in 89% of neurons with intense substance P receptor immunoreactivity, and in 1.5% of neurons with weak substance P receptor immunoreactivity. Neuropeptide Y immunoreactivity was also observed in 92% of neurons with intense immunoreactivity for substance P receptor, and in 1.6% of neurons with weak immunoreactivity for substance P receptor. In contrast, parvalbumin immunoreactivity was seen in 1.3% of neurons with intense substance P receptor immunoreactivity, and in 59% of weak substance P receptor immunoreactivity. Calbindin D28k immunoreactivity was found in 12 and 19% of neurons, respectively, with weak and intense immunoreactivities for substance P receptor. Virtually no cells showing substance P receptor immunoreactivity displayed immunoreactivity for vasoactive intestinal polypeptide or choline acetyltransferase. These results indicate that the neocortical neurons expressing substance P receptor constitute a subpopulation of GABAergic non-pyramidal cells, and are segregated into neurons with intense immunoreactivity and those with weak immunoreactivity for substance P receptor; the vast majority of neurons with intense substance P receptor immunoreactivity contain somatostatin and neuropeptide Y, and the majority of neurons with weak substance P receptor immunoreactivity have parvalbumin.
Kaneko
T
T
Department of Morphological Brain Science, Faculty of Medicine, Kyoto University, Japan.
Shigemoto
R
R
Nakanishi
S
S
Mizuno
N
N
D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D009479:Neuropeptides / Q000276:immunology / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018040:Receptors, Neurokinin-1 / Q000276:immunology / Q000378:metabolism*
D009479:Neuropeptides; D018040:Receptors, Neurokinin-1