[Cardiovascular alpha- and beta-adrenoceptor sensitivities in orthostatic dysregulation]

Orthostatic dysregulation (OD), originally a German-Scandinavian term partially corresponding to an Anglo-American concept of sympathotonic orthostatic hypotension, is characterised by altered cardiovascular control on standing, and its clinical features include dizziness, palpitation and, occasionally, orthostatic hypotension. The symptomatology suggests presence of cardiovascular adrenoceptor dysfunction, although the aetiology of OD has not been elucidated. The above situation prompted us to investigate autonomic nervous function in OD. The subjects were 8 patients with OD (20 +/- 2 years old; mean +/- SD), all of them fulfilled the diagnostic criteria accepted in Japan, and 6 healthy controls (17 +/- 3 years old). Noradrenaline and isoproterenol infusion tests and conventional haemodynamic functional tests (70 degrees passive head-up tilt, cold pressor test, Valsalva manoeuvre and Aschner's eye-ball pressure test) were carried out upon the subjects under the continuous measurement of blood pressure, pulse rate and respiration. Plasma vasoactive substances (noradrenaline, adrenaline, arginine-vasopressin and renin activity) were also determined in supine position and at 15 minutes after the 70 degrees passive head-up tilt. In noradrenaline infusion test, different doses (0.01 microgram/kg, 0.02 microgram/kg, 0.05 microgram/kg and 0.1 microgram/kg) of noradrenaline were administered by means of intravenous bolus injection, and a degree of subsequent rise in blood pressure was used as an index for the cardiovascular alpha-adrenoceptor sensitivity. In isoproterenol infusion tests cardiovascular beta 1- and beta 2-adrenoceptor sensitivities were assessed, respectively, by a degree of an increase in pulse rate and a degree of a fall in blood pressure following bolus injection of the drug (0.001 microgram/kg, 0.002 microgram/kg, 0.005 microgram/kg and 0.01 microgram/kg).(ABSTRACT TRUNCATED AT 250 WORDS)