Organization of the Catecholaminergic System in the Short-Lived Fish Nothobranchius furzeri

The catecholaminergic system has received much attention based on its regulatory role in a wide range of brain functions and its relevance in aging and neurodegenerative diseases. In the present study, we analyzed the neuroanatomical distribution of catecholaminergic neurons based on tyrosine hydroxylase (TH) immunoreactivity in the brain of adult Nothobranchius furzeri. In the telencephalon, numerous TH+ neurons were observed in the olfactory bulbs and the ventral telencephalic area, arranged as strips extending through the rostrocaudal axis. We found the largest TH+ groups in the diencephalon at the preoptic region level, the ventral thalamus, the pretectal region, the posterior tuberculum, and the caudal hypothalamus. In the dorsal mesencephalic tegmentum, we identified a particular catecholaminergic group. The rostral rhombencephalon housed TH+ cells in the locus coeruleus and the medulla oblongata, distributing in a region dorsal to the inferior reticular formation, the vagal lobe, and the area postrema. Finally, scattered TH+ neurons were present in the ventral spinal cord and the retina. From a comparative perspective, the overall organization of catecholaminergic neurons is consistent with the general pattern reported for other teleosts. However, N. furzeri shows some particular features, including the presence of catecholaminergic cells in the midbrain. This work provides a detailed neuroanatomical map of the catecholaminergic system of N. furzeri, a powerful aging model, also contributing to the phylogenetic understanding of one of the most ancient neurochemical systems.

Evolutionary Modifications Are Moderate in the Astroglial System of Actinopterygii as Revealed by GFAP Immunohistochemistry

The present paper is the first comparative study on the astroglia of several actinopterygian species at different phylogenetical positions, teleosts (16 species), and non-teleosts (3 species), based on the immunohistochemical staining of GFAP (glial fibrillary acidic protein), the characteristic cytoskeletal intermediary filament protein, and immunohistochemical marker of astroglia. The question was, how the astroglial architecture reflexes the high diversity of this largest vertebrate group. The actinopterygian telencephalon has a so-called ‘eversive’ development in contrast to the ‘evagination’ found in sarcopterygii (including tetrapods). Several brain parts either have no equivalents in tetrapod vertebrates (e.g., torus longitudinalis, lobus inferior, lobus nervi vagi), or have rather different shapes (e.g., the cerebellum). GFAP was visualized applying DAKO polyclonal anti-GFAP serum. The study was focused mainly on the telencephalon (eversion), tectum (visual orientation), and cerebellum (motor coordination) where the evolutionary changes were most expected, but the other areas were also investigated. The predominant astroglial elements were tanycytes (long, thin, fiber-like cells). In the teleost telencephala a ‘fan-shape’ re-arrangement of radial glia reflects the eversion. In bichir, starlet, and gar, in which the eversion is less pronounced, the ‘fan-shape’ re-arrangement did not form. In the tectum the radial glial processes were immunostained, but in Ostariophysi and Euteleostei it did not extend into their deep segments. In the cerebellum Bergmann-like glia was found in each group, including non-teleosts, except for Cyprinidae. The vagal lobe was uniquely enlarged and layered in Cyprininae, and had a corresponding layered astroglial system, which left almost free of GFAP the zones of sensory and motor neurons. In conclusion, despite the diversity and evolutionary alterations of Actinopterygii brains, the diversity of the astroglial architecture is moderate. In contrast to Chondrichthyes and Amniotes; in Actinopterygii true astrocytes (stellate-shaped extraependymal cells) did not appear during evolution, and the expansion of GFAP-free areas was limited.

Characterization of cholecystokinin binding sites in goldfish brain and pituitary

The characterization and distribution of cholecystokinin (CCK)/gastrin binding sites were determined in the goldfish central nervous system (CNS). Binding of 125I-sulfated CCK octapeptide (125I-CCK-8s) in tissue sections was found to be saturable, reversible, time dependent, and displaceable by CCK/gastrin-like peptides. Analysis of saturable equilibrium binding revealed a high-affinity binding site (dissociation constant of 0.706 +/- 0.188 nM), which also displayed high affinity for gastrin-17s and caerulein. Lower affinities were observed for the nonsulfated forms of CCK-8 and gastrin-17. These findings suggest that a single primitive CCK/gastrin receptor exists in the goldfish CNS. The distribution of CCK/gastrin binding sites in the goldfish brain and pituitary revealed high densities within the telencephalon and preoptic hypothalamus, as well as within hypothalamic nuclei associated with the brain feeding center. High densities of binding sites were also localized within the midbrain tegmentum and optic tectum of the midbrain, the facial lobe and vagal lobe of the hindbrain, and within the pituitary pars distalis. Overall, these findings support previous studies that indicate that CCK/gastrin-like peptides play a role in the central regulation of feeding behavior and pituitary hormone secretion in fish.

Body Colour Changes Induced By Spinal Thermal Stimulation Of The Crucian Carp (Carassius Carassius)

1. Body colour changes of the crucian carp during spinal thermal stimulation were recorded photoelectrically. 2. Warming the spinal cord induced darkening, whereas cooling induced lightening of body colour. 3. After transection of the medulla oblongata posterior to the vagal lobe, the same colour responses as in intact fish were induced, apart from one of the seven responses to spinal cooling. 4. After spinal pithing, thermal stimulation of the spinal cord failed to induce the responses. 5. The present responses are considered to indicate influence of spinal thermal stimulation on the cutaneous sympathetic systems of this fish.