| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2001: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2000: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
1. Studies on the nature and projection area of the posterior amygdaloid neurons
( 1 ) Fluoro-gold and Fluoro-red were injected into medial prefrontal cortex (mPFC) and hypothalamus respectively and retrogradely labeled neurons were examined in the amygdala. Double labeled neurons were found in the posterior amygdaloid nucleus(PA), hippocampal CA1 ,CA3 and subiculum. The double labeled neurons projected by axon collaterals to the hypothalamic nuclei (ventromedial and medial premammillary nucleus) and to the medial prefrontal cortex.
(2) Neurons in the PA were investigated using immunohistochemical technique for estrogen receptor-α (ER-α), calbindin, pervalbumin, as well as for GABA. ER-α immunoreactive neurons occupied almost 100% of neurons in female and 45% in male PA of the rat. GABA containing neurons were 5% and calbindin and pervalbumin containing neurons were 5% and 6% respectively in both sexes.
(3) PA sends projections to the mPFC. Using biotinylated dextran amine (BDA) as an ant
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erograde axonal tracer and immunohistochemistry for pervalbumin and calbindin as markers of interneurons, synaptic structures were examined in the mPFC. A dense network of axon terminals of PA neurons were observed in the 2-3rd layers of the infralimbic cortex in the mPFC. A close contact between axon varicosities and pervalbumin or calbindin immunoreactive neurons were observed indicating that PA neurons project to the interneurons in the infralimbic cortex.
2. Changes of reaction pattern to conditioned fear stress after lesioning of posterior amygdaloid nucleus
Functional and morphological analysis of limbic and autonomic related area and behavioral evaluation have been performed on conditioned fear after contextual conditioning of the rat. Preliminary results obtained were as follows : The effect of chronic mild stress was examined and a) After 5 days mild conditioning (0.6mA, 3sec X 30 times, 30min/day), % freezing time was significantly increased (43%) compared with control (4%). b) After 4 days mild conditioning, serum concentration of corticosterone was significantly increased (35.3ng/nl) compared with control (3.2ng/nl). c) c-Fos expression in the limbic and autonomic related area of the brain showed no remarkable change. After excessive footshock conditioning (0.6mA,3sec X 60times, 30min/day), freezing time was saturated by 1 day and serum concentration of corticosterone showed maximum increase on day 2 and no significant change was observed after 3 days. We are going on conditioned fear experiment on rat under the new experimental design. Less
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