The chapter considers the overall organization of the main parts of
brain in cyprinoid fish. It is described general cytoarchitectonical acpects
of location, elements of neural structure and the system of relations in the
most important centers of brainstem, and the forebrain - as the highest
integrative center of the fish brain. It is presented a new data about adult
neurogenesis and neurochemical (mediator) architectonics of the carp
brain. It is described the some zones of neurogenesis in the adult carp
brain, comparative data about immunolocalization of hydrogen sulphide
producing enzyme the cystathionine β-synthase, NADPH-diaphorase and
tyrosine hydroxylase in the different regions of carp brain. It is discussed
the involvement of these neurotransmitters and gaseous intermediators in the regulation of neurotransmission in the different brain centers and
processes of adult neurogenesis.
Catecholaminergic (CA-ergic) systems in the brainstem of carp were
studied using immunohistochemical labeling of tyrosine hydroxylase.
The peculiarities of localization of medullary neurons, morphology of the
dendrites, and trajectories of the axon projections in the medulla of the
carp allow us to differentiate three groups of neurons, namely
interfascicular cells, units related to the lobus vagus, and cells localized
within the area postrema. In the periventricular region of this cerebral
zone, we found phenotypically immature forms of the TH-ip cells. We
hypothesize that, in carp, dopamine functions as an inductor of
development (morphogenetic factor) and is involved in adult
neurogenesis in matrix zones of the brain.
H2S-producing cells and fibers are located in all parts of the brain
carp and may participate in the modulation other neurotransmitter
systems of the brain. NADPH-d-producing cells have been identified in
different parts of the brain: habenular nuclei, medial hypothalamus,
isthmus, reticular formation and ventral column of spinal cord. Most of
these nuclei in the brain cyprinoid fish are cholinergic centers. Thus, in
carp brain nitric oxide can be considered as a modulator of cholinergic
neurotransmission. In the carp brain have been found populations H2Sproducing cells in the areas of primary and secondary neurogenesis. H2Sproducing cells have been identified in the periventricular area of
diencephalon, medulla oblongata and granular eminentia of cerebellum.
We believe that H2S may participate in the processes regulation of adult
neurogenesis, cells migration and differentiation in these areas of the
brain. Among all NO-producing cells in the adult carp brain was
discovered population of NADPH-d positive cells, which had a high level
of enzyme activity and located on the dorsal surfaces of telencephalon.
This zone is a border of embryonic eversion, where activity of
proliferative nuclear antigen was identified. Radial-oriented fibers and
cells with a high activity of NADPH-d have been revealed in medial
thalamus, marginal layer of optical tectum and external wall of brainstem.
NADPH-d positive cells in these areas had a high level of enzyme
activity, large nucleus located in central part of cells and high value of
nuclear-cytoplasmic ratio. We believe that NO-producing cells are also
involved in adult neurogenesis, because NADPH-d positive cells are
located on the territory of secondary neurogenesis zones. However, H2Sproducing and NO-producing populations of cells in the carp brain have
different spatial localizations. Thus, we believe that during the adult
neurogenesis in carp brain may be involved various signaltransductor
systems.