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Neuronal pathways for urotensins and other neuropeptides in the central nervous system of fishes
110
Neuronal pathways for urotensins central nervous system of fishes.
and
other
neuropeptides
in the
K. Lederis I, R. Yulis 2, J. Fryer 3 and G. Gonzalez I Iuniversity of Calgary and 3University Universidad Austral, Valdivia, Chile.
of Ottawa,
Canada and
Urotensin I and II are neuropeptides isolated from the urophysis (caudal neurosecretory system; Cau N.S.) of bony fishes. Additional neuronal systems specific for either U I or UII, have recently been identified in different regions of the central nervous system (CNS) of various fishes. Urotensin I, which is a close structural and biological homologue of the mammalian corticotropin releasing hormones (CRF), has been found also in a separate population of hypothalamic parvocellular neurons in the lateral tuberal area of Catostomus commersoni and Carassius auratus. Moreover, U I is equipotent with the CRF in stimulation of ACTH secretion in mammals and significantly more potent as compared with the mammalious CPF in stimulation of fish ACTH release. An anterior spinal, central canal CSF-contacting UII system consisting of parvocellular neurons, located just ventral from the central canal and extending throughout the length of the spinal cord up to the brain stem has been described in detail in Catostomus c. and identified in all fresh and seawater fishes examined, including the Acipenseridae and Chimaera (Belenky, Polenov and Lederis, unpublished observations). The function of this extensive anterior spinal UII system has not been defined. However, the presence of multiple well defined fibre tracts (the medial longitudinal bundle, bilateral (ventrolateral) fibre tracts and projections from these to a peripheral-meningeal vasculative contacting fibre system suggests strongly an integrative, perhaps neurosensory or even neurotransmitting function for this very extensive system and its fibre network. Such an integrative role is further supported by neural connections between this UII system, and another population of parvocellular somatostatinspecific (SST) neurons axo-axonal or axo-somatic connections with the neurons of the anterior spinal UII system, including apparent terminations of SST - reacting nerve fibres around the parikarya of unidentified neurons. Findings of currently ongoing immunocytochemical studies designed to determine (a) the distribution of substance P (SP) - specific neuronal elements throughout the Catostomus central nervous system and (b) any relationship between the SP and the U I or UII or SST systems, will be discussed.
Neuronal pathways for urotensins central nervous system of fishes.
and
other
neuropeptides
in the
K. Lederis I, R. Yulis 2, J. Fryer 3 and G. Gonzalez I Iuniversity of Calgary and 3University Universidad Austral, Valdivia, Chile.
of Ottawa,
Canada and
Urotensin I and II are neuropeptides isolated from the urophysis (caudal neurosecretory system; Cau N.S.) of bony fishes. Additional neuronal systems specific for either U I or UII, have recently been identified in different regions of the central nervous system (CNS) of various fishes. Urotensin I, which is a close structural and biological homologue of the mammalian corticotropin releasing hormones (CRF), has been found also in a separate population of hypothalamic parvocellular neurons in the lateral tuberal area of Catostomus commersoni and Carassius auratus. Moreover, U I is equipotent with the CRF in stimulation of ACTH secretion in mammals and significantly more potent as compared with the mammalious CPF in stimulation of fish ACTH release. An anterior spinal, central canal CSF-contacting UII system consisting of parvocellular neurons, located just ventral from the central canal and extending throughout the length of the spinal cord up to the brain stem has been described in detail in Catostomus c. and identified in all fresh and seawater fishes examined, including the Acipenseridae and Chimaera (Belenky, Polenov and Lederis, unpublished observations). The function of this extensive anterior spinal UII system has not been defined. However, the presence of multiple well defined fibre tracts (the medial longitudinal bundle, bilateral (ventrolateral) fibre tracts and projections from these to a peripheral-meningeal vasculative contacting fibre system suggests strongly an integrative, perhaps neurosensory or even neurotransmitting function for this very extensive system and its fibre network. Such an integrative role is further supported by neural connections between this UII system, and another population of parvocellular somatostatinspecific (SST) neurons axo-axonal or axo-somatic connections with the neurons of the anterior spinal UII system, including apparent terminations of SST - reacting nerve fibres around the parikarya of unidentified neurons. Findings of currently ongoing immunocytochemical studies designed to determine (a) the distribution of substance P (SP) - specific neuronal elements throughout the Catostomus central nervous system and (b) any relationship between the SP and the U I or UII or SST systems, will be discussed.