AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 2 371-R375, Copyright © 1990 by American Physiological Society
Noradrenergic and neuropeptide Y mechanisms in guanethidine-sympathectomized rats
E. E. Benarroch, J. D. Schmelzer, K. K. Ward, D. K. Nelson and P. A. Low
Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905.
The cardiovascular responses to sympathomimetic agents, the norepinephrine
(NE) content in peripheral tissues, and the tissue content and
cardiovascular effects of neuropeptide Y (NPY) were examined in
anesthetized adult rats with guanethidine-induced sympathectomy (GuSx). We
observed blunted pressor responses to tyramine, exaggerated pressor
responses to phenylephrine, and markedly reduced NE contents in the atrium,
femoral artery, superior cervical ganglion (SCG), and sciatic and vagus
nerves. When tyramine responses were corrected for the NE content in the
SCG, GuSx rats were similar to controls. A depletion of NPY levels in
tissue resulted in an increased sensitivity to the pressor effects of
intravenous NPY administration. GuSx, therefore, reproduces findings of
postganglionic adrenergic failure in humans. Responses to the
administration of sympathomimetic agents may reflect the degree of
noradrenergic denervation. NPY may be a potential marker of chronic
postganglionic sympathetic denervation in cardiovascular tissue.
