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A developmental study of substance‐P, somatostatin, enkephalin, and serotonin immunoreactive elements in the spinal cord of the North American opossum
Author(s) -
DiTirro F. J.,
Martin G. F.,
Ho R. H.
Publication year - 1983
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.902130302
Subject(s) - opossum , biology , spinal cord , anatomy , marsupial , somatostatin , enkephalin , marginal zone , substance p , central nervous system , white matter , baboon , neuropeptide , endocrinology , neuroscience , zoology , medicine , biochemistry , receptor , b cell , radiology , opioid , magnetic resonance imaging , antibody , immunology
Substance‐P (SP), somatostatin (SOM), enkephalin (ENK), and serotonin (5‐HT) immunoreactive elements were studied in the spinal cord of the opossum at each 10‐mm snout‐rump (S‐R) length interval between 18 (newborn) and 127 mm (75 days after birth). The opossum is born 12 days after conception and undergoes a protracted postnatal development in an external pouch which makes it a good model for such a study. SP‐like immunoreactivity was detected in the newborn opossum; it was found within fibers located mainly in the dorsolateral marginal zone. SP‐like immunoreactive fibers soon become fairly abundant within presumptive laminae I, II, and X and were scattered within other areas of the spinal gray matter including the intermediolateral cell column. By 30 days after birth (57 mm S‐R length), the adult distribution was established. SOM‐like immunoreactivity was not detected within the spinal cord at birth. However, by postnatal day 5 (24 mm S‐R length) it was present in fibers which were numerous within the marginal zone and present within presumptive laminae I–III as well as in more ventral areas of the gray matter. By approximately postnatal day 30, evidence for SOM immunoreactivity was found within all areas of the spinal gray matter expected from studies of the adult opossum. ENK‐like immunoreactivity was present at birth within fibers of the dorsolateral marginal zone. By postnatal day 30 ENK immunoreactive fibers were found within most of the areas containing them in the adult animal, except for laminae I and II. ENK‐like immunoreactivity was not observed in laminae I and II until approximately postnatal day 50 (84 mm S‐R length). Fibers showing 5‐HT‐like immunoreactivity were remarkably abundant within the cervical marginal zone at birth but sparse at lumbosacral levels. They were found within laminae IV–Xby postnatal day 15 (35 mm S‐R length) and within the intermediolateral cell column by at least day 30. The adult distribution was not present until approximately 50 days after birth when 5‐HT‐like immunoreactivity was found within fibers of laminae I and II. Demonstration of SOM‐, ENK‐, and 5‐HT‐like immunoreactivities in neuronal somata of the spinal cord was age dependent. Our results suggest that axons containing SP, SOM, ENK, and 5‐HT are present within the opossum's spinal cord very early in development and that they grow into specific spinal targets in an orderly sequence.