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Immunohistochemical analysis of the relation between 5‐hydroxytryptamine‐ and neuropeptide‐immunoreactive elements in the spinal cord of an amphibian ( Xenopus laevis )
Author(s) -
Pieribone Vincent A.,
Brodin Lennart,
Hökfelt Tomas
Publication year - 1994
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.903410406
Subject(s) - biology , spinal cord , neuropeptide , galanin , xenopus , amphibian , substance p , anatomy , calcitonin , medicine , endocrinology , neuroscience , gene , ecology , biochemistry , receptor
In mammals, a large proportion of the bulbospinal 5‐hydroxytryptamine (5‐HT) neurons also contain neuropeptides, such as substance P (SP) and galanin (GAL). To examine whether a similar coexistence occurs in an amphibian, an immunofluorescence double‐labelling technique was employed on sections of the Xenopus laevis spinal cord. Antisera raised against SP, GAL, enkephalin (ENK), corticotropin‐releasing factor (CRF), calcitonin gene‐related peptide (CGRP), and cholecystokinin (CCK) produced a labelling of fibers at all rostrocaudal levels of the spinal cord, with the highest fiber densities for SP and ENK and intermediate densities for GAL, CCK, and CGRP, while CRF‐immunoreactive fibers were barely detectable in intact animals. 5‐HT‐immunoreactive fibers were widely distributed in the spinal cord, and they often occurred in the vicinity of different types of peptide‐immunoreactive fibers. However, no coexistence between 5‐HT and the different peptide immunoreactivities could be detected, although SP and GAL immunoreactivities were sometimes found to be colocalized in the same fiber. Similar negative results were obtained when 5‐HT + SP‐ and 5‐HT + GAL‐labelled sections were examined in single focal planes with a confocal microscope. After a spinal transection, (survival period 6 weeks to 4 months), almost all 5‐HT‐immunoreactive fibers below the lesion were lost, and a build‐up of immunoreactive material occurred in fibers just rostral to the cut. In contrast, no significant loss of peptide‐immunoreactive fibers occurred, although some swollen SP‐, GAL‐, ENK‐, CRF‐, and CCK‐immunoreactive fibers were present rostral to the cut. The distribution of swollen peptide‐immunoreactive fibers did not overlap with that of the swollen 5‐HT‐immunoreactive fibers. Although negative immunohistochemical data must be inter‐preted with caution, in conjunction with previous studies (Brodin et al. [1988] J. Comp. Neurol. 271:1‐18; Sakamoto and Atsumi [1991] Cell Tissue Res. 264:221‐230), the present results indicate that bulbospinal 5‐HT neurons in nonmammalian vertebrates cocontain neuropeptides to a lesser extent than in mammals.