Gadolinium attenuates exercise pressor reflex in cats

• Published in: American journal of physiology. Heart and circulatory physiology 2001-05, Vol.280 (5), p.H2153-H2161
• Main Authors: Hayes, Shawn G, Kaufman, Marc P
• Format: Article
• Language: English
• Subjects: Achilles Tendon - innervation; Achilles Tendon - physiology; Anesthetics, Intravenous; Animals; Anti-Inflammatory Agents - pharmacology; Autonomic Nervous System - cytology; Autonomic Nervous System - physiology; Blood Pressure - physiology; Capsaicin - pharmacology; Cats; Chloralose; Decerebrate State; Dose-Response Relationship, Drug; Gadolinium - pharmacology; Heart Rate - physiology; Mechanoreceptors - physiology; Muscle Contraction - physiology; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Neurons, Afferent - physiology; Physical Exertion - physiology; Reflex, Stretch - drug effects; Reflex, Stretch - physiology; Respiration
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.280.5.h2153

Division of Cardiovascular Medicine, Departments of Internal Medicine and Human Physiology, University of California, Davis, California 95616 The exercise pressor reflex, which arises from the contraction-induced stimulation of group III and IV muscle afferents, is widely believed to be evoked by metabolic stimuli signaling a mismatch between blood/oxygen demand and supply in the working muscles. Nevertheless, mechanical stimuli may also play a role in evoking the exercise pressor reflex. To determine this role, we examined the effect of gadolinium, which blocks mechanosensitive channels, on the exercise pressor reflex in both decerebrate and -chloralose-anesthetized cats. We found that gadolinium (10 mM; 1 ml) injected into the femoral artery significantly attenuated the reflex pressor responses to static contraction of the triceps surae muscles and to stretch of the calcaneal (Achilles) tendon. In contrast, gadolinium had no effect on the reflex pressor response to femoral arterial injection of capsaicin (5 µg). In addition, gadolinium significantly attenuated the responses of group III muscle afferents, many of which are mechanically sensitive, to both static contraction and to tendon stretch. Gadolinium, however, had no effect on the responses of group IV muscle afferents, many of which are metabolically sensitive, to either static contraction or to capsaicin injection. We conclude that mechanical stimuli arising in contracting skeletal muscles contribute to the elicitation of the exercise pressor reflex. group III and IV muscle afferents; contraction; tendon stretch; capsaicin; autonomic nervous system