THE EFFECT OF HIGH INTENSITY WHITE NOISE ON THE ULTRASTRUCTURE OF AXO-DENDRITIC SYNAPSES IN COLLICULUS INFERIOR OF ADULT MALE CATS. QUANTITATIVE ELECTRON MICROSCOPIC STUDY

Environmental noise is a serious problem for the society and medicine. Chronic loud noise is known to produce numerous adverse effects on different levels of the organism. In addition to behavioral changes, the involvement of different regions of the brain was documented. The analysis of structural modifications provoked by noise in brain give the possibility to suggest that one of the effects of noise may be the alterations in neurotransmission. Therefore, of special interest should be the elucidation of the effects of chronic noise on the fine structure of synapses of brain areas participating in the processing of auditory information. In the present study, using transmission electron microscope. We elucidate the effects of high intensity chronic white noise on the morphology of axo-dendritic synapses, and size and diameter of synaptic vesicles in auditory region, inferior colliculus of adult male cats. Experimental animals were exposed to 100 dB (5-20 kHz) white noise for one hour per day, for 10 consecutive days. On 11th day, after special procedures, the area of interest was examined under electron microscope. In ~ 15% large synaptic terminals the clustering of synaptic vesicles, as well as swelling, partial vacuolization or degeneration of presynaptic mitochondria were detected. Morphometric analysis of docked (with presynaptic membrane) and undocked synaptic vesicle size revealed that docked vesicles are smaller than undocked vesicles. It was observed in both control and experimental animals, however, in experimental animals, such difference was more significant. Such results suggest that due to continuous transmission, the majority of vesicles are unable to replenish their cargo via transporters. Evaluation of synaptic vesicles size undertaken in the current electron microscopic study has advanced the understanding of the pathophysiology of white noise exposure on auditory brain processing regions, in addition to our understanding of fractional neurotransmitter release at the nerve terminal and on overall brain function.

FINE ARCHITECTURE OF THE HIPPOCAMPUS IN ADOLESCENT, ADULT AND AGED RATS. ELECTRON MICROSCOPIC STUDY

The study included adolescents (P30-36), adult (P125-130) and aged (P330-340) male Wistar rats - 4 animals in each age group. The rats were housed individually, in wire-top polypropylene cages (30-cm width x 30 cm length x 25 cm height) and maintained on a 12-h light/dark cycle. Standard food pellets and tap water were ad libitum. The animal maintenance and electron microscopic procedures were conducted in accordance with European Union Directive on the protection of animals used for scientific research. The Ultrastructure of adult and adolescent rats are almost same. However, remarkable changes are expressed between adult and senescent rats. Precisely, in the last one there are following ultrastructural modifications - lipofuscin concentrations, small destructive cytoplasmic organelles, changes in presynaptic vesicular and mitochondrial quantity. Rare apoptotic signs in neurons. Analysis of all this means that aging in rat's hippocampus causes selective changes, also it underlines changes in neurotransmission and neuronal developmental pathways.

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.