AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 4 1045-R1051, Copyright © 1991 by American Physiological Society
Blood pressure maintenance in hypertensive sympathectomized rats. I. Adrenal medullary catecholamines
M. Lo, C. Julien, C. Barres, F. Boomsma, C. Cerutti, M. Vincent and J. Sassard
Departement de Physiologie et Pharmacologie Clinique, Centre National de la Recherche Scientifique, Unite de Recherche Associee 606, Faculte de Pharmacie, Lyon, France.
To assess the role of the sympathetic nervous system in the development of
genetic hypertension, blood pressure (BP) was recorded in conscious adult
Lyon hypertensive (LH) and normotensive (LN) rats that had received daily
injections of saline or guanethidine at 1-13 wk of age. Guanethidine
abolished the pressor response to tyramine, decreased plasma norepinephrine
by greater than 70% and plasma 3,4-dihydroxyphenylglycol by approximately
90%, and did not change plasma epinephrine. Bilateral adrenalectomy further
reduced plasma norepinephrine to 8 and 5% of control levels in LH and LN
rats, respectively. BP was lowered (-7%) in sympathectomized rats, but the
mean absolute BP difference between LH and LN rats was unaltered. Despite
marked supersensitivity to alpha-adrenoreceptor stimulation, phentolamine
induced only a small transient depressor response, which was abolished by
adrenalectomy in sympathectomized rats. It is concluded that the
sympathetic nervous system is not necessary for the development of
hypertension in LH rats. After sympathectomy, circulating catecholamines,
which mostly derive from the adrenal medulla, play only a minor role in BP
maintenance.
