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Expression of c-fos in response to stressogenic stimuli in the amygdala of old vs. young rats ? a preliminary study

100%
Boguszewski P., Zagrodzka J.
Acta Neurobiologiae Experimentalis
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2005
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vol. 65
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issue 2
191-194
EN
During aging many of the brain functions became deteriorated or altered. One of the most important age related changes is an increase of anxiety level, reported both in humans and in animals. Our study was intended to compare c-fos gene expression in amygdala, the key structure in anxiety/fear regulation, in old (24 months old) and young (4 months old) rats exposed to various behavioral stimulations. There were no differences between age groups in basal c-Fos expression. After social encounter c-Fos expression level in amygdala increased significantly, but still remained independent on age. Significant differences between both groups appeared after open field test and immobilization test. Contrary to the findings on young adults indicating the correlations between increased anxiety level and higher c-Fos expression, old rats showed increased anxiety together with significantly lower c-Fos expression.
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Bicuculline administration into ventromedial hypothalamus: effects on fear and regional brain monoamines and GABA concentrations in rats

81%
Zagrodzka J., Romaniuk A., Wieczorek M., Boguszewski P.
Acta Neurobiologiae Experimentalis
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2000
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vol. 60
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issue 3
333-343
EN
The effects of bicuculline methiodide administration into ventromedial hypothalamus (15 ng per site, bilaterally) on fear behavior and monoamines (NA, DA, 5-HT) and GABA in structures of the brain defensive system (hypothalamus, midbrain gray matter, amygdala, hippocampus and frontal cortex) were studied. Fear behavior was examined in the modified version of light-dark transition test. The time out from the illuminated compartment of chamber, the time spent there and number of returns to the illuminated compartment was measured. Additionally motor activity, i.e., number of crossings and rearings in dark as well as in the illuminated part of compartment, was registered. Blockade of GABAA receptors in the ventromedial hypothalamus resulted in increased fear behavior, i.e. decrease of time out from illuminated compartment and decrease of the time spent there. Motor behavior remained unchanged. HPLC analysis showed reduction of GABA concentration in all investigated brain structures. An increase of NA concentration in all examined structures with exception of the hypothalamus without effect on MHPG/NA was observed as well. Dopamine level remained unchanged, but DOPAC/DA ratio increased in all structures, except frontal cortex. Also HVA/DA ratio increased in the hypothalamus and midbrain. 5-HT concentration increased only in midbrain, 5-HIAA increased in midbrain and in frontal cortex, and 5-HIAA/5-HT ratio increased only in frontal cortex. These results indicate that GABA-ergic and monoaminergic systems remain in functional interactions and that these interactions may play an important role in the neurochemical regulation of fear behavior. The possible mechanism of GABA - monoaminergic interactions is discussed.
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