Characterization of neocortical non-pyramidal neurons expressing preprotachykinins A and B: a double immunofluorescence study in the rat.
Neurons expressing preprotachykinin A and preprotachykinin B, which are the precursor prepropeptides of substance P and neurokinin B (neuromedin K), respectively, were characterized immunocytochemically in the rat neocortex. Antibodies raised against C-terminal portions of preprotachykinins were used for labeling cell bodies of preprotachykinin-producing neurons. Neurons immunoreactive for preprotachykinin B were encountered four times more frequently in the neocortex than those immunoreactive for preprotachykinin A. Preprotachykinin A-immunoreactive neurons were scattered more frequently in the deep cortical layers (layers IV-VI) than in the superficial layers (layers I-III), whereas preprotachykinin B-immunoreactive neurons were distributed more frequently in the superficial layers than in the deep layers. Almost all preprotachykinin-expressing neurons were immunoreactive for GABA, suggesting that they were non-pyramidal cells. However, co-expression of the two preprotachykinin immunoreactivities in single neurons was not found. Preprotachykinin-expressing neocortical neurons were further examined with markers for subpopulations of GABAergic cortical neurons. Immunoreactivities for parvalbumin, calbindin and somatostatin were found in 69%, 27% and 11%, respectively, of preprotachykinin A-immunoreactive neurons. Conversely, preprotachykinin A-immunoreactive neurons constituted only 6% of parvalbumin-immunoreactive neurons, 4% of calbindin-immunoreactive neurons and 1% of somatostatin-immunoreactive neurons. Immunoreactivities for calretinin, choline acetyltransferase, vasoactive intestinal polypeptide, corticotropin-releasing factor and cholecystokinin were detected in 13-39% of preprotachykinin B-immunoreactive neurons. Preprotachykinin B immunoreactivity was seen in 33% of calretinin-positive neurons, 45% of cholinergic neurons, 47% of vasoactive intestinal polypeptide-positive neurons, 59% of corticotropin-releasing factor-positive neurons and 83% of cholecystokinin-positive neurons. These results indicate that preprotachykinin A- and preprotachykinin B-expressing neurons constitute separate populations of GABAergic non-pyramidal neurons in the neocortex. Since receptors for substance P and neurokinin B are expressed in GABAergic neurons [Kaneko T. et al. (1994) Neuroscience 60, 199-211] and pyramidal neurons [Ding Y. Q. et al. (1996) J. comp. Neurol. 364, 290-310], respectively, cortical neurons may use two separate lines of tachykinin signals; substance P serves as a signal between GABAergic non-pyramidal neurons, whereas neurokinin B acts as a signal of GABAergic neurons to pyramidal neurons.
Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Japan.
T
T
Kaneko
M
M
Murashima
T
T
Lee
N
N
Mizuno
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D000918:Antibody Specificity; D015415:Biomarkers / Q000032:analysis; D002795:Choline O-Acetyltransferase / Q000032:analysis; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D006168:Guinea Pigs; D007150:Immunohistochemistry; D008959:Models, Neurological; D008969:Molecular Sequence Data; D019579:Neocortex / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000032:analysis; D009474:Neurons / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D009928:Organ Specificity; D011498:Protein Precursors / Q000032:analysis / Q000096:biosynthesis*; D011817:Rabbits; D051381:Rats; D015398:Signal Transduction; D009435:Synaptic Transmission; D015320:Tachykinins / Q000032:analysis / Q000096:biosynthesis*
D000906:Antibodies; D015415:Biomarkers; D000939:Epitopes; D009419:Nerve Tissue Proteins; D011498:Protein Precursors; D015320:Tachykinins; C044206:preprotachykinin; D002795:Choline O-Acetyltransferase