Rostroventral medulla-mediated biphasic modulation of the rat cardiosomatic motor reflex

• Published in: Neuroscience Vol. 185; pp. 174 - 182
• Main Authors: Sun, N, Liu, X.-H, Du, J.-Q, Zhu, J.-X, Tang, J.-S, Li, Q
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 30.06.2011; Elsevier
• Subjects: Adrenergic alpha-2 Receptor Antagonists - pharmacology; Anesthetics, Local - pharmacology; Animals; Biological and medical sciences; biphasic modulation; Capsaicin - pharmacology; cardiosomatic motor reflex; Dose-Response Relationship, Drug; Electric Stimulation - methods; electrical stimulation; Electromyography; Evoked Potentials, Motor - drug effects; Evoked Potentials, Motor - physiology; Functional Laterality - drug effects; Fundamental and applied biological sciences. Psychology; intrapericardial capsaicin; Lidocaine - pharmacology; Male; Medulla Oblongata - drug effects; Medulla Oblongata - physiology; Naloxone - pharmacology; Narcotic Antagonists - pharmacology; Neural Pathways - drug effects; Neural Pathways - physiology; Neurology; pain modulation; Rats; Rats, Sprague-Dawley; Reflex - drug effects; Reflex - physiology; rostroventral medulla; Sensory System Agents - pharmacology; Spinal Cord Injuries - pathology; Vertebrates: nervous system and sense organs; Yohimbine - pharmacology; electrical stimulation; DMSO; RVM; CMR; dorsolateral funiculus; TRPV1; rostroventral medulla; electromyogram; pain modulation; TMUD; VF; VLF; dimethyl sulfoxide; ventral funiculus; biphasic modulation; cardiosomatic motor reflex; total number of motor unit discharges; IC; transient receptor potential vanilloid-1; intrapericardial capsaicin; EMG; ventrolateral funiculus; DLF; Reflex; Rat; Capsaicin; Electrical stimulus; Rodentia; Central nervous system; Encephalon; Vertebrata; Mammalia; Pain; Animal; Medulla oblongata
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2011.04.016

Abstract The purpose of the present study was to examine whether the rostroventral portion of the medulla oblongata (RVM) exerts descending modulation on the cardiosomatic motor reflex (CMR) in rats. Capsaicin (1 μg/ml, 0.2 ml) was injected into the pericardial sac as an algesic substance to induce the CMR, which was monitored via electromyogram (EMG) responses of dorsal spinotrapezius muscle to the noxious cardiac stimulus. Descending modulation of the CMR was observed by electrical or chemical stimulation of RVM. Specifically, electrical stimulation of RVM produced facilitatory, inhibitory or biphasic effects on the CMR evoked by noxious cardiac stimulation, depending on stimulation intensity. In addition, glutamate receptor activation in RVM replicated the effects of electrical stimulation. Lidocaine interruption of the ventrolateral funiculus/ventral funiculus (VLF/VF) or transection of the dorsolateral funiculus (DLF) revealed that the descending facilitatory and inhibitory influences from RVM were conveyed via the VLF/VF and DLF, respectively. Furthermore, intrathecal administration of naloxone or yohimbine partly reversed the inhibitory effect of RVM electrical stimulation, suggesting that opioid and noradrenergic systems are involved in descending RVM modulation of the CMR.