TY - JOUR
T1 - High levels of mRNA coding for substance P, somatostatin and α-tubulin are expressed by rat and rabbit dorsal root ganglia neurons
AU - Boehmer, Christian G.
AU - Norman, Jill
AU - Catton, Mark
AU - Fine, Leon G.
AU - Mantyh, Patrick W.
N1 - Funding Information:
A select population of DRG neurons with thin axons synthesize an array of peptides (17, 18, 21, 37, 41). The growing list of "sensory" neuropeptides includes: calcitonin gene-related peptide tx and [3, corticotrophin releasing factor, dynorphin, galanin, gastrin releasing peptide, somatostatin (SOM), neurokinin A, substance P (SP) and vasoactive intestinal polypeptide. It has become increasingly evident in the last decade that neuropeptid e-containing DRG neurons which convey afferent somatosensory information from peripheral tissues to the spinal cord are also involved in the efferent regulation of the peripheral tissues they innervate (8, 27, 28, 32, 33). Efferent functions of these sensory neuropeptides include vasodilation, plasma extravasation, pavementing of leukocytes, mast cell degranulation, and regulation of the inflammatory, immune and wound healing responses (27,28). If sensory neurons regulate such a diverse set of functions this would imply that a significant amount of neuropeptide must be synthesized and released at both the central and peripheral terminals. Immunochemical studies of several prototypic sensory neuropeptides including SOM and SP indicate that the total amount of peptide present in the DRG neuron is quite low when compared to neurons in other brain regions (5, 11, 23). For example, when SP levels are measured by radioimmunoassay there is 92 ng SP/g protein in the rat DRG, while in other brain areas such as the striatum there is 781 ng SP/g protein (23). This difference is also apparent when immunohistochemistry is used to study neuropeptide-containing neurons. The neuropeptide levels in DRG neurons are usually so low that pretreatment with colchicine (a substance which blocks microtubule formation, inhibiting axoplasmic flow, and thereby causing an accumulation of the peptide in the cell body) is often required to increase the peptide to detectable levels. This step is not necessary for immunohistochemical visualization tThis work was supported by the American Paralysis Association, the Amyotrophic Lateral Sclerosis Association, a Sloan Fellowship to P.W.M. and NIH grant No. NS-23970. 2Requests for reprints should be addressed to Dr. Patrick Mantyh, Center for Brain Sciences (151), VA Medical Center, Minneapolis, MN 55417.
PY - 1989
Y1 - 1989
N2 - Oligonucleotide probes complementary to α-tubulin, preprotachykinin A (PPT A), preprosomatostatin (PPSOM), and preproarginine-vasopressin (PPAVP) mRNA were hybridized to sections of rat and rabbit brain and dorsal root ganglia (DRG) at all spinal levels. Approximately 100% of the DRG neurons in the rat and rabbit express α-tubulin mRNA, 20-30% express PPT A mRNA and 5-17% express PPSOM mRNA. Whereas neurons which express PPSOM mRNA are of relative uniform size, the neurons which express PPT A mRNA segregate into two broad groups. One group is composed of smaller neurons (200-2,000 μm2) which contain an extremely dense concentration of PPT A mRNA. The second group is composed of larger neurons (2,000-3,500 μm2) which contain a moderate concentration of PPT A mRNA. PPAVP mRNA is present in very high concentrations in the paraventricular and supraoptic nucleus of the rat hypothalamus but is not detected in any DRG neurons. In both the rat and the rabbit the density of PPT A and PPSOM mRNA is high in individual DRG neurons in comparison to PPT A and PPSOM mRNA levels contained in most forebrain neurons. These results suggest that although the level of neuropeptide present in DRG neurons is relatively low in comparison to other brain areas, the rate of sensory neuropeptide synthesis and turnover, as reflected by mRNA content, is extremely high.
AB - Oligonucleotide probes complementary to α-tubulin, preprotachykinin A (PPT A), preprosomatostatin (PPSOM), and preproarginine-vasopressin (PPAVP) mRNA were hybridized to sections of rat and rabbit brain and dorsal root ganglia (DRG) at all spinal levels. Approximately 100% of the DRG neurons in the rat and rabbit express α-tubulin mRNA, 20-30% express PPT A mRNA and 5-17% express PPSOM mRNA. Whereas neurons which express PPSOM mRNA are of relative uniform size, the neurons which express PPT A mRNA segregate into two broad groups. One group is composed of smaller neurons (200-2,000 μm2) which contain an extremely dense concentration of PPT A mRNA. The second group is composed of larger neurons (2,000-3,500 μm2) which contain a moderate concentration of PPT A mRNA. PPAVP mRNA is present in very high concentrations in the paraventricular and supraoptic nucleus of the rat hypothalamus but is not detected in any DRG neurons. In both the rat and the rabbit the density of PPT A and PPSOM mRNA is high in individual DRG neurons in comparison to PPT A and PPSOM mRNA levels contained in most forebrain neurons. These results suggest that although the level of neuropeptide present in DRG neurons is relatively low in comparison to other brain areas, the rate of sensory neuropeptide synthesis and turnover, as reflected by mRNA content, is extremely high.
KW - Dorsal root ganglion
KW - In situ hybridization
KW - Neurokinin A
KW - Somatostatin
KW - Substance P
KW - mRNA
KW - α-Tubulin
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U2 - 10.1016/0196-9781(89)90011-9
DO - 10.1016/0196-9781(89)90011-9
M3 - Article
C2 - 2482965
AN - SCOPUS:0024829170
SN - 0196-9781
VL - 10
SP - 1179
EP - 1194
JO - Peptides
JF - Peptides
IS - 6
ER -