Yohimbine-induced alterations of monoamine metabolism in the spontaneously hypertensive rat. I. The peripheral nervous system.
The effects of alpha 2 adrenoreceptor blockade with YOH on blood pressure, plasma catecholamines and norepinephrine (NE) stores in kidney, adrenal and spleen of spontaneously hypertensive rats of the Okamoto strain (SHR) and Wistar-Kyoto (WKY) control animals were examined. YOH administration resulted in a significant (p less than 0.001) reduction in arterial pressure in both SHR and WKY. Plasma NE and EPI were significantly (p less than 0.05) elevated by YOH treatment in both SHR and WKY, but SHR exhibited a significantly (p less than 0.05) greater percent increase in plasma NE than WKY. YOH produced significant decreases in splenic NE content in both SHR and WKY but reduced renal NE content in the SHR only. SHR had significantly higher basal renal NE and DA content and fewer NE uptake (3H-desmethylimipramine binding) sites (p less than 0.05) than WKY. Treatment of SHR or WKY with either the alpha 2-adrenergic antagonist, idazoxan, or the alpha 1-antagonist, prazosin, failed to significantly alter renal NE levels from those found after saline injection. The enhanced YOH-induced renal NE depletion in SHR suggests an alteration in the presynaptic control of NE release in the genetically hypertensive rat, however, the effects of YOH in the SHR may be mediated by mechanisms unrelated to alpha 2-adrenergic receptors.
Dawson
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R
Cardiovascular Research and Training Center, University of Alabama, Birmingham 35294.
Nagahama
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S
Oparil
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S
D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D003891:Desipramine / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008297:Male; D010525:Peripheral Nerves / Q000187:drug effects* / Q000503:physiopathology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D011941:Receptors, Adrenergic / Q000378:metabolism; D013045:Species Specificity; D013154:Spleen / Q000187:drug effects / Q000378:metabolism; D015016:Yohimbine / Q000008:administration & dosage / Q000494:pharmacology*
D002395:Catecholamines; D011941:Receptors, Adrenergic; D015016:Yohimbine; D003891:Desipramine