E V Pushchina
National Scientific Center of Marine Biology Far Eastern Branch, Russia
Title: Histochemistry and cytochemistry in neurochemical studies of brain and adult neurogenesis
Biography
Biography: E V Pushchina
Abstract
Histochemical and cytochemical studies central nervous system (CNS) of vertebrates have made a significant contribution
to understanding how specific neurotransmitter systems of brain are working. The formaldehyde-induced fluorescence
(FIF) technique has been of great value because it offered, for the first time, the opportunity to map catecholamines (CAs).
The FIF method was developed following the discovery that sections of formaldehyde-fixed adrenal medulla that produces
CAs were fluorescent. This technique allowed labeling of catecholaminergic cells and fibers in various tissues including the
rat brain. Later, the treatment of tissue with glyoxylic acid was preferentially used because it was more sensitive compared
to the FIF method. Acetylcholine (ACh) is a classic neurotransmitter that is widely distributed in the CNS efferent systems,
as well as in some specialized intra-cerebral systems. Until the 1980s, quantitative biochemical assays for ACh and choline
acetyltransferase (ChAT) and histochemical techniques for acetylcholinesterase (AChE) were the methods used to locate
putative cholinergic neurons. Histochemical methods for determining AChE revealed a number of putative cholinergic
somas and fibers in the CNS of vertebrates. Nitric oxide (NO) has recently been shown to play a fundamental role in the
development and plasticity of the central nervous system CNS, during both embryonic and post-embryonic life stages.
Histochemical identification NO-ergic neurons with using NADPH-diaphorase allowed study topography and morphology
of the NADPH-d positive neurons and nuclei in the CNS of vertebrates. Thus, neuro-histochemical and cytochemical studies
have to describe structure, localization, topography and connections of various neurotransmitter systems, become the
first step in investigation of neurochemistry of brain. Currently, a unified view to physiological mechanisms of integration
of different neurotransmitter modulating systems in fish brain is not formed. The results of study different species of
teleost fish showed significant intergroup differences in organization as a nonspecific (dopaminergic, cholinergic, etc.),
and specific afferent projections in forebrain. The signals coming from the so-called non-specific systems of brain have
often role of secondary neuromodulators, initiating a long plastic reconstructions of inter-neuronal interactions, providing
a direct connection between sensory and motor centers, during creating of motor programs of behavior. The ascending
systems of brain activation in teleost fishes have essential features associated with the organization of sensory systems
and their central projections, a predominance of one or another types of analyzers, wide adaptive radiation, low level of
brain cephalization, as well as special type of CNS histogenesis. Objective of our work is to investigate the organization,
projection features and relationships of signal transduction systems, producing classic neurotransmitters (catecholamines,
acetylcholine, gamma-aminobutyric acid) and gaseous intermediates (nitric oxide and hydrogen sulfide), in fish brain and
evaluate their participation in the processes of adult neurogenesis of the CNS.