| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1997: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1996: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
To compensate for water liss in sea water, eels drink the sea water and absorbed it through the intestine. However, the intestine can not absorb water from the sea water directly. If highly concentrated NaCl enters into the intestine, eels stopped the drinking, which was due to luminal Cl^- Na^+ itself enhanced the drinking behavior. The drinking behavior was altered 20 min after Na^+ or Cl^- reached to the intestine. Therefore, we expected some hormonal substances secreted from the intestine might regulate drinking behavior. When angiotensin II (ANGII), histamine (HA), serotomin (5-HT), carbochol, isoproterenol, prolactin, or substance P was injected into the posterior cardinal vein, the drinking was depressed. On the other hand, atrial natriuretic peptide (ANP), vasotocin, smatostatin, phenylephrine, vasoactive intestinal peptide (VIP), cholecystokinin (CCK8), peptide YY,and eel intestinal pentapeptide (EIPP) stopped the drinking. Because all these reagents act from the blood, the dr
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inking center was suspected to be a part of the circumventricular organs, where no blood-brain barrier exist. When Evans Blue was injected intraperitoneally, dorsal part of the medulla oblongata, ventral part of the cerebelum and basal part of the saccus vasculosus in the brain were atained, indicating absence of blood-brain barrier in these areas. We also observed that the effects of HA and 5-HT were via ANGII,suggesting that ANGII is one of candidates which act directly on the brain. Therefore, in the next experiments, ANGI-fluorescen was applied to the section of the eel brain. Specific fluorescence was observed at the dorsal part of the medulla oblongata and at the basal part of the saccus vasculosus. Altogether, the dorsal part of the medulla oblongata and the basal part of the saccus vasculosus may be a part of drinking center in eels. Although EIPP isolated from eel intestine depressed drinking behavior, EIPP was not detected in the incubation medium by HPLC after perfusing the intestine with high concentrated C^-. Less
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