I Yamaguchi

National Institute of Mental Health (NIMH), Maryland, United States

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Publications (2)2.58 Total impact

  • G Feuerstein, I Yamaguchi, I J Kopin
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    ABSTRACT: Injection of muscimol (4 mg/kg, i.a.) to unanesthetized SHR rats reduced the arterial blood pressure and heart rate more than in WKY rats. These cardiovascular responses were accompanied by a moderate increase in plasma norepinephrine level and a marked increase in plasma epinephrine level, in the SHR rats. In the WKY rats, only a moderate increase in plasma epinephrine level was seen. Injection of subconvulsive doses of picrotoxin (2 mg/kg, i.a.) or bicuculline (1 mg/kg, i.a.) to SHR rats, elicited a higher and a more prolonged increase of the arterial blood pressure than in WKY rats. Plasma norepinephrine and epinephrine levels increased to the same extent in both the SHR and WKY rats following picrotoxin injection. These results suggest that the SHR rats differ from the WKY rats in the reactivity of GABAergic responses in cardiovascular centers which also modulate the peripheral sympathetic tone.
    Clinical and experimental hypertension 02/1981; 3(2):207-18. · 1.29 Impact Factor
  • I J Kopin, R McCarty, I Yamaguchi
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    ABSTRACT: Plasma levels of norepinephrine reflect the rate of its release from sympathetic nerves. In patients with hypertension and in spontaneously hypertensive (SHR) rats basal plasma NE levels are normal. SHR rats are abnormally reactive to stress, as are the normotensive (WKY) strain from which they were derived. The amounts of NE released by sympathetic stimulation are similar in pithed SHR and WKY rats, but SHR rats have greater blood pressure responses. This may be due to diminished beta-adrenoceptor-mediated vasodilation in young SHR rats and structural changes in arterioles of older SHR rats. It is concluded that in SHR rats separate abnormalities of centrally-mediated responses to stress and of peripheral sensitivity to catecholamines contribute to the development and maintenance of elevated blood pressure.
    Clinical and experimental hypertension 02/1980; 2(3-4):379-94. · 1.29 Impact Factor

Publication Stats

19 Citations
2.58 Total Impact Points


  • 1980–1981
    • National Institute of Mental Health (NIMH)
      • Laboratory of Clinical Science
      Maryland, United States