High-salt-induced increase in blood pressure: role of capsaicin-sensitive sensory nerves.
OBJECTIVE
To test the hypothesis that sensory afferents are significant functional components in preventing salt-induced increases in blood pressure.


METHODS
Neonatal Wistar rats were subcutaneously injected with 50 mg/kg capsaicin or vehicle on the first and second days of life. After weaning, male rats were divided into three groups and treated for 4 weeks with: control plus normal (0.5%, CON-NS) or high (4%, CON-HS) sodium diet, and capsaicin pretreatment plus HS diet (CAP-HS). Mean arterial pressure (MAP) and its response to bolus injection of calcitonin gene-related peptide (CGRP) and its antagonist, CGRP(8-37), were measured by carotid arterial catheterization. Radioimmunoassay was used to measure CGRP levels in plasma and dorsal root ganglia (DRG). Expression of components of the CGRP receptor, calcitonin receptor-like receptor (CRLR) and receptor activity modifying protein 1 (RAMP1), was determined by the use of Western blot analysis.


RESULTS
Baseline MAP was increased in CAP-HS compared with CON-HS and CON-NS rats, and it was higher in CON-HS than in CON-NS rats. MAP response to exogenous CGRP was enhanced in CAP-HS and CON-HS than in CON-NS rats, but MAP response to CGRP(8-37) was increased only in CON-HS rats. Plasma CGRP levels were not different among three groups, but CGRP content in DRG was decreased in CAP-HS compared with CON-HS and CON-NS rats. CRLR expression in mesenteric resistance arteries was upregulated in CAP-HS and CON-HS compared with CON-NS rats, but RAMP1 content was not different among these groups.


CONCLUSIONS
Chronic high-salt intake upregulates expression of mesenteric CGRP receptors without altering CGRP levels in plasma and DRG. Increased expression of mesenteric CGRP receptors may play a counter regulatory role in attenuating salt-induced increases in blood pressure.
Li
Jianping
J
Department of Medicine, Michigan State University, East Lansing, MI 48824, USA.
Wang
Donna H
DH
D000818:Animals; D000831:Animals, Newborn; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology*; D015740:Calcitonin Gene-Related Peptide / Q000037:antagonists & inhibitors / Q000502:physiology; D002211:Capsaicin / Q000633:toxicity*; D005727:Ganglia, Spinal / Q000502:physiology; D006973:Hypertension / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008955:Models, Cardiovascular; D008959:Models, Neurological; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000502:physiology; D012982:Sodium, Dietary / Q000008:administration & dosage*
D018015:Receptors, Calcitonin Gene-Related Peptide; D012982:Sodium, Dietary; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin