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Cardiac vanilloid receptor 1-expressing afferent nerves and their role in the cardiogenic sympathetic reflex in rats.
- Source :
-
The Journal of physiology [J Physiol] 2003 Sep 01; Vol. 551 (Pt 2), pp. 515-23. Date of Electronic Publication: 2003 Jun 26. - Publication Year :
- 2003
-
Abstract
- Myocardial ischaemia causes the release of metabolites such as bradykinin, which stimulates cardiac sensory receptors to evoke a sympathoexcitatory reflex. However, the molecular identity of the afferent neurons and fibres mediating this reflex response is not clear. In this study, we tested the hypothesis that the cardiogenic sympathoexcitatory reflex is mediated by capsaicin-sensitive afferent fibres. Enhanced immunofluorescence labelling revealed that vanilloid receptor 1 (VR1)-containing afferent nerve fibres were present on the epicardial surface of the rat heart. Resiniferatoxin (RTX), a potent analogue of capsaicin, was used to deplete capsaicin-sensitive afferent fibres in rats. Depletion of these fibres was confirmed by a substantial reduction of VR1 immunoreactivity in the epicardium and dorsal root ganglia. The thermal sensitivity was also diminished in RTX-treated rats. Renal sympathetic nerve activity (RSNA) and blood pressure were recorded in anaesthetized rats during epicardial application of bradykinin or capsaicin. In vehicle-treated rats, epicardial bradykinin (10 microg ml-1) or capsaicin (10 microg ml-1) application produced a significant increase in RSNA and arterial blood pressure. The RSNA and blood pressure responses caused by bradykinin and capsaicin were completely abolished in RTX-treated rats. Furthermore, epicardial application of iodo-RTX, a highly specific antagonist of VR1 receptors, blocked capsaicin- but not bradykinin-induced sympathoexcitatory responses. Thus, these data provide important histological and functional evidence that the heart is innervated by VR1-expressing afferent nerves and these afferent nerves are essential for the cardiogenic sympathoexcitatory reflex during myocardial ischaemia.
- Subjects :
- Animals
Blood Pressure drug effects
Bradykinin pharmacology
Capsaicin pharmacology
Diterpenes
Fluorescent Antibody Technique
Ganglia, Spinal physiology
Heart innervation
Hot Temperature
Kidney innervation
Kidney physiology
Male
Microscopy, Confocal
Myocardium metabolism
Neurons, Afferent metabolism
Nociceptors drug effects
Pain Measurement drug effects
Rats
Rats, Sprague-Dawley
Reaction Time drug effects
Receptors, Drug biosynthesis
Heart physiology
Neurons, Afferent physiology
Receptors, Drug physiology
Reflex physiology
Sympathetic Nervous System physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0022-3751
- Volume :
- 551
- Issue :
- Pt 2
- Database :
- MEDLINE
- Journal :
- The Journal of physiology
- Publication Type :
- Academic Journal
- Accession number :
- 12829722
- Full Text :
- https://doi.org/10.1113/jphysiol.2003.048207