Immunohistochemical investigation of urotensins in the caudal spinal cord of four species of elasmobranchs and the lamprey, Lampetra japonica

Abstract

In the four species of elasmobranchs examined (Triakis scyllia, Heterodontus japonicus, Scyliorhinus torazame, Dasyatis akajei), all identifiable caudal neurosecretory cells and their corresponding neurohemal areas showed urotensin II (UII)-immunoreactivity with varied intensity. To localize urotensin I (UI) in the caudal neurosecretory system of the dogfish, Triakis scyllia, h-CRF (1-20) antiserum that cross-reacts with UI was used in place of UI antiserum. CRF/UI-immunoreactivity was demonstrated in the neurosecretory cells and neurohemal areas. A considerable number of neurons showed both UII- and CRF/UI-immunoreactivities, suggesting that UII and UI are produced in the same neurosecretory cells. However, some neurons exhibited UII-immunoreactivity, but no CRF/UI-immunoreactivity. Cells immunoreactive only to CRF antiserum were not detected. At least two populations of neurons exist in the dogfish caudal neurosecretory system: (i) cells immunoreactive for both CRF/UI and UII, and (ii) cells immunoreactive for UII. The dorsal cells of the lamprey, Lampetra japonica, did not react with either UII or CRF antiserum.

Immunohistochemical localization of urotensins I and II in the caudal neurosecretory neurons of the carp Cyprinus carpio and the sharks Heterodontus japonicus and Cephaloscyllium umbratile.

“…The axons of neurons of both types terminated in the neurohemal areas. These results were similar to those demonstrated by CRF and Ull antisera in the dog fish, Triakis scyllia (OWADA et al, 1985b). FISHER et al (1984) observed that all the caudal neurosecretory neurons in the white sucker reacted with UI antiserum, and considered the hypothesis for the existence of two types of neurons containing UI and UII, respectively, to be untenable.…”

“…The UI-immunoreactive neurons were first demonstrated in elasmobranchs in the present study, although a CRF/UI-like substance has already been demonstrated using CRF antiserum (.OwADA et al, 1985b). At least two types of neurons were identified: those immunoreactive with both UI and Ull antisera ( Fig.…”

“…Neurons producing UI were immunohistochemically localized by FISHER et al (1984) in the caudal neurosecretory system of the white sucker, Catostomus commersoni, using an antiserum to UI of the same species. Further, antisera to the corticotropin-releasing factor (CRF) and sauvagine were successfully used to localize a UI-like substance, since CRF and sauvagine have several amino acid sequences homologous with UI (CRF: LARSON et al, 1984;ONSTOTT and ELDE, 1984;BERN et al, 1985;OWADA et al, 1985b;YAMADA et al, 1985;sauvagine: RENDA et al, 1982). Neurons producing UII were also immunohistochemically located in several species of teleosts (LARSON et al, 1984;OWADA and KOBAYASHI, 1984;BERN et al, 1985;OWADA et al, 1985a;YAMADA et al, 1985) and in elasmobranchs (OWADA et al, 1985b).…”

“…Further, antisera to the corticotropin-releasing factor (CRF) and sauvagine were successfully used to localize a UI-like substance, since CRF and sauvagine have several amino acid sequences homologous with UI (CRF: LARSON et al, 1984;ONSTOTT and ELDE, 1984;BERN et al, 1985;OWADA et al, 1985b;YAMADA et al, 1985;sauvagine: RENDA et al, 1982). Neurons producing UII were also immunohistochemically located in several species of teleosts (LARSON et al, 1984;OWADA and KOBAYASHI, 1984;BERN et al, 1985;OWADA et al, 1985a;YAMADA et al, 1985) and in elasmobranchs (OWADA et al, 1985b). In these studies, several investigators noted the co-localization of a CRF-or UI-like (CRF/UI) substance and UII in the same neurons in teleosts (LARSON et al, 1984;BERN et al, 1985;YAMADA et al, 1985) and in elasmobranchs (OWADA et al, 1985b As rabbit antiserum to carp UI has recently become available, in the present study we used UI antiserum instead of CRF antiserum to localize UI and also to examine the possible coexistence of UI and UII in the same neurons of the caudal neurosecretory system of the carp and two species of shark.…”

“…In the goby, Gillichthys mirabilis, two types of neurons were reported: those with both CRF/UI-and UII-immunoreac- tivities and those with only CRF/UI-immunoreactivity (LARSON et al, 1984;BERN et al, 1985). Further, two types of neurons were reported in the dogfish, Triakis scyllia: those with both CRF/UI-and UII-immunoreactivities and those with only UII-immunoreactivity (OWADA et al, 1985b). In the present study, using antisera to UI and UII, we demonstrated three types of neurons in the carp: those with only UI-immunoreactivity, those with only UII-immunoreactivity, and those with both UI-and UII-immunoreactivities and two types of neurons in two species of shark: those with only UII-immunoreactivity and those with both UI-and UII-immunoreactivities.…”