“…In previous studies in hypertensive man and animals the rise in vascular resistance has been reported to be due to changes in non-autonomic factors and increased autonomic constrictor tone (Mendlowitz & Touroff, 1952;Conway, 1963;Cohn, Liptak & Freis, 1963;Korner, Shaw, Uther, West, McRitchie & Richards, 1973). However, in all these studies measurements after block have been made at a lower blood pressure than before block (Cohn et al, 1963;Korner et al, 1973;Tarazi & Dustan, 1973).…”