Submitted on September 21, 2004
Accepted on May 4, 2005
Calcitonin Gene-Related Peptide and Substance P Contribute to the Reduced Blood Pressure in Sympathectomized Rats
S. C Supowit1*, R. T Ethridge2, H. Zhao3, K. A Katki1, and D. J DiPette1
1 Medicine, Texas A&M University System Health Science Center College of Medicine, Temple, TX, USA
2 Scott & White Memorial Hospital and Clinic, Temple, TX, USA
3 Surgery, University of Texas Medical Branch, Galveston, TX, USA
* To whom correspondence should be addressed. E-mail: ssupowit{at}swmail.sw.org.
CGRP and SP are produced in dorsal root ganglia (DRG) sensory neurons and modulate vascular tone. Sympathetic and sensory nerves compete for nerve growth factor (NGF), a potent stimulator of CGRP and SP, and it has been suggested that sympathetic hyperinnervation in spontaneously hypertensive rats may reduce the availability of NGF to sensory nerves thus reducing CGRP and SP. The purpose of this study was to determine whether destruction of peripheral sympathetic nerves in normal rats would increase the availability of NGF for sensory neurons and enhance expression of CGRP and SP. Sympathectomy was produced in rats by guanethidine administration. Control rats received saline. Sympathectomized rats displayed reductions in blood pressure (BP) and atria norepinephrine levels while NGF levels in DRG, spleen, and ventricles were increased. Sympathectomy also enhanced CGRP and SP mRNA and peptide content in DRG. Administration of CGRP and SP receptor antagonists increased the BP in sympathectomized rats but not the controls. Thus, sympathectomy enhances sensory neuron CGRP and SP expression that contributes to the BP reduction.
