EFFECT OF ARSENIC EXPOSURE ON BEHAVIOR OF RATS OF VARIOUS AGE GROUPS.

Arsenic is ranked first among toxicants posing a significant potential threat to human health based on known or suspected toxicity. Recent animal studies suggest that the brain is the major target of arsenic exposure. The present study demonstrates the effect of Arsenic compounds on behavior changes in different age (young and adult) groups of rats. In order to study anxiety behavior, learning and memory processes we used open field, elevated plus maze, spontaneous alteration behavior and multi-branched maze tests. Our experiments revealed that 68 mg/L (35 ppm) Sodium (meta) arsenite (when animals got arsenic from drinking water for three months) induces more significant effect on body weight gain in adult rats rather than in young ones. Arsenic exposure may result in rat's emotional instability despite the animals' age. According to the spontaneous alteration test, obtained data revealed that behavior is changed only in adult rats compared to control ones. Also it was found that Arsenic consumption at the same concentration induces considerable difficulties in learning process (multi-branched maze test results) in the adult arsenic exposed group. We have found differences in maze test performance, during fulfilling memory tasks by arsenic exposed animals in comparison to control ones. This distinction was mostly notable in young groups. These data show that Arsenic exposure affects short-term memory more dramatically in adult animals rather than of young ones, whereas difficulties in long-term memory were detected among young animals.

Effect of chronic inhalation of toluene on behavior of rats of various age groups in multi-branched maze.

The effect of a 40-day toluene inhalation on learning of young and adult rats was examined in a multi-branched maze. Experimental rats of both age groups needed more time to pass the maze and made more errors than controls. This impairment was observed in young rats immediately after termination of toluene inhalation and in adult rats immediately and 90 days after toluene.

Stress-system: corticotropin-releasing hormone and catecholamines (review).

The brain's stress-handling system--the limbic-hypothalamic-pituitary-adrenal axis--is one of the most thoroughly studied circuitry of the central nervous system. As a result of stress-axis activation different behavioral and physical changes develop; these changes allow the organism to adapt. For this purpose stress-system closely "works" with other elements of central nervous system, which are involved in the regulation of emotion and structures, also with axes, responsible for reproduction, growth and immunity. Dysfunction of stress-system--it's hyper- or hypoactivity--is characteristic peculiarity of many pathological states and disorders. Various molecules (corticotropin-releasing hormone, vasopressin, glucocorticoids, mineralocorticoids, ACTH, its precursor proopiomelanocortin etc.) are engaged in the regulation of stress-axis. Among these molecules corticotropin-releasing hormone is supposed to have a key role in regulating the response to stress. Besides these molecules, the end-products of the stress-axis activation: catecholamines, different hormones and cytokines - control the activity of multiple levels of this axis. According some views catecholamines play one of the essential roles in the alterations provoked by stress-axis activation. In this review we cite some classical (Crousseau et al.) and modern data concerning corticotropin-releasing hormone and catecholamine activities during stress.

[Quantitative analysis of gliocytes and macrogliocyte-neuronal ratio in the rat hippocampus after kindling].

Gliosis is one of the main morphological correlates of epilepsy. It is presented predominantly by proliferation and hypertrophy of astrocytes and activated microglia (macrophages) and is most characteristic to those areas of the epileptogenic zones, where the loss of neurons is significant. One of such structures is the hippocampus, the sclerosis of which develops already at the early stages of epileptogenesis. Using the slides stained with cresylviolet, the quantitative analysis of gliocytes and of macrogliocyte-neuronal ratio was performed in all the areas of the hippocampus 14 and 30 days after electrical kindling. After both time intervals, the decrease of the number of neurons and the increase of the number of gliocytes were found in all the regions of the hippocampus. After 14 days the changes of gliocytes were particularly significant in the radial and oriental layers of the Ammon's horn, after 30 days they were also pronounced in CA3 pyramidal cell layer of and in hilus. Thus, hippocampal gliocytes are actively involved in the epileptogenesis.

[Layer-to-layer distribution of neurons and macroglial cells in various zones of the cat auditory cortex (quantitative study)]. / Posloinoe raspredelenie neiro- i makrogliotsitov v razlichnykh zonakh slukhovoi kory mozga koshek (kolichestvennoe issledovanie).

Quantitative analysis of layer-to-layer distribution of neurons and macrogliocytes in zones AI, AII, Ep and Ins of cat brain was performed in specimens stained after Einarson. Zones of auditory cortex were shown not to differ in density of neuron distribution. In every zone the neuron number in layers II, III and VI was significantly higher than in layers IV and V and in layers III and IV of zones AI and AII the number of neurons with macroglial satellites was almost twices higher than in the same layers of zones Ep and Ins. Fraction of neurons with different number of satellites shows significant diversities as well. In layers IV, V and VI of zones AI and AII both total number of macrogliocytes and perineuronal satellites was significantly higher than in zones Ep and Ins. The number of perineuronal satellitocytes correlates both with neuron axonal length and the level of the cell functional activity.