Relationship among blood pressure, tail blood flow and plasma catecholamine levels in chronic spinal rats.

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In chronic spinal rats, relationship among the systemic blood pressure (BP), the tail blood flow and plasma catecholamines, noradrenaline (NA) and adrenaline (AD). Spinal cord of adult Wistar Kyoto rat (WKY) was transected at lower cervical portion, and the rats were reared as chronic spinal rats in a warm room (30ﾟC). The systemic blood pressure (BP) was measured by the tail cuff method, in other cases BP was measure by a pressure transducer at the femoral artery. Heart rate (HR) was calculated by of R-R interval of a ECG.Blood sample was drawn through the cannula of the jugular vein under conscious condition. Plasma level of NA and AD were estimated by HPLC.RESULTS : A : Effect of the acute spinalization : Spinal cord was transected at level of Th1 (Group-A) or C7 (Group-B) of the vertebral segment. In Group-A rats, Th1 spinal nerve remain intact which contain the cardiac sympathetic nerve fibers (Waibl H,1973). In Group-A,acute spinalization induced a sustained increase of HR and co … More re temperature gradually increased after the spinalization, BP decreased slightly. Only Group-A rats survived after the spinaliztion. B : Pharmacological studies of blood vessels of the tail. Intermediate condition (not constricted but not fully dilated) was kept in chronic spinal rats. Either propranolol (beta-adrenergic antagonist, 8 mg/kg) or isoproterenol (beta-adrenergic agonist, 0.1 mg/kg) induced a transient tail vasoconstriction. C : plasma level of NA and AD : By the spinal transection, systemic BP was decreased from 120 mmHg to 80 mmHg. BP recovered gradually day by day but did not attained level of normal value as reported by Osborn (Am J Physiol, 1989). Mean NA level (mean <plus-minus> S.E) was 50<plus-minus>32 pg/ml (N=6) in the 1st week (W) after the spinalization, and 147<plus-minus>42 pg/ml (N=7) in the 2nd W.Value in the 2nd W was significantly (P<0.05) high compared to value of 1st W.Mean AD was 594<plus-minus>324 pg/ml in the 1st W and 309<plus-minus>153 pg/ml in the 2nd W,there was no significant difference between these values. From these results, it is suggested that humoral factors from adrenal medulla and others are more important for the regulation of the blood vessels in chronic sp Less