title: The rostral ventromedial medulla control of cutaneous vasomotion of paws and tail in the rat: implication for pain studies.
abstract: Thermal neutrality in rodents is achieved by large cyclic variations of the sympathetic drive of the vasomotion of the tail and paws, the most widely used target organs in current acute or chronic animal models of pain. Given the pivotal functional role of rostral ventromedial medulla (RVM) in nociception and rostral medullary raphe (rMR) in thermoregulation, two largely overlapping brain regions, we aimed at circumscribing the brainstem regions that are the source of premotor afferents to sympathetic preganglionic neurons that control the vasomotor tone of the tail and hind paws. A thermometric infrared camera recorded indirectly the vasomotor tone of the tail and hind paws. During the control period, the rat was maintained in vasoconstriction by preserving a stable, homogeneous, and constant surrounding temperature, slightly below the core temperature. The functional blockade of the RVM/rMR by the GABAA receptor agonist muscimol (0.5 nmol, 50 nl) elicited an extensive increase of the temperature of the paws and tail, associated with a slight decrease of blood pressure and heart rate. Both the increased heat loss through vasodilatation and the decrease heart-induced heat production elicited a remarkable reduction of the central temperature. The effective zones were circumscribed to the parts of the RVM/rMR facing the facial nucleus. They match very exactly the brain regions often described as specifically devoted to the control of nociception. Our data support and urge on the highest cautiousness regarding the interpretation of results aimed at studying the effects of any pharmacological manipulations of RVM/rMR with the usual tests of pain.
authors.affiliation: Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France; and.
authors.forename: Nabil
authors.initials: N
authors.lastname: El Bitar
authors.affiliation: Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France; and.
authors.forename: Bernard
authors.initials: B
authors.lastname: Pollin
authors.affiliation: Institute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Gan
authors.initials: G
authors.lastname: Huang
authors.affiliation: Institute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: André
authors.initials: A
authors.lastname: Mouraux
authors.affiliation: Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France; and daniel.le_bars@upmc.fr.
authors.forename: Daniel
authors.initials: D
authors.lastname: Le Bars
mesh_terms: D000818:Animals; D001794:Blood Pressure; D001833:Body Temperature Regulation; D005121:Extremities / Q000294:innervation / Q000502:physiology; D058785:GABA-A Receptor Agonists / Q000494:pharmacology; D006339:Heart Rate; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D059225:Nociception; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000098:blood supply / Q000294:innervation*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D013623:Tail / Q000294:innervation / Q000502:physiology; D014661:Vasoconstriction; D014664:Vasodilation
chemical_list: D058785:GABA-A Receptor Agonists
keywords: RVM; ambient temperature; blood pressure; environmental impact; heart rate; infrared camera; rMR; rat; rostral medullary raphe; rostral ventromedial medulla; skin temperature; thermoregulation