title: Muscarinic receptors within the ventromedial hypothalamic nuclei modulate metabolic rate during physical exercise.
abstract: The involvement of muscarinic cholinoceptors within the ventromedial hypothalamic nuclei (VMH) on the exercise-induced increase in oxygen consumption (VO(2)) was investigated. Rats were fitted with bilateral cannulae into the VMH for local delivery of drugs. On the day of the experiments, the animals were submitted to running exercise (20 m/min; 5% grade) until the point of fatigue. VO(2) was continuously measured after bilateral injections of either 0.2 μL of 5 × 10(-9)mol methylatropine or 0.15M NaCl solution into the VMH. Control experiments were conducted in freely moving rats on the treadmill. Muscarinic blockade within the VMH reduced time to fatigue by 32% and enhanced the increase in VO(2) from the 8th until the 17th min of exercise when compared to the control trial. In fact, time to fatigue was negatively correlated to the rate of increase in VO(2) (r(2)=0.747; P<0.001). However, bilateral injections of methylatropine in freely moving rats did not change VO(2) in comparison to saline injections. In conclusion, muscarinic cholinoceptors within the VMH are activated during exercise to modulate the increase in metabolic rate. Furthermore, blocking muscarinic transmission leads to a faster increase in VO(2) that is associated with the early interruption of exercise.
authors.affiliation: Endocrinology and Metabolism Laboratory, Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Samuel Penna
authors.initials: SP
authors.lastname: Wanner
authors.forename: Juliana Bohnen
authors.initials: JB
authors.lastname: Guimarães
authors.forename: Washington
authors.initials: W
authors.lastname: Pires
authors.forename: Umeko
authors.initials: U
authors.lastname: Marubayashi
authors.forename: Nilo Resende Viana
authors.initials: NR
authors.lastname: Lima
authors.forename: Cândido Celso
authors.initials: CC
authors.lastname: Coimbra
mesh_terms: D000818:Animals; D001286:Atropine Derivatives / Q000494:pharmacology; D004734:Energy Metabolism / Q000502:physiology*; D005221:Fatigue / Q000503:physiopathology; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010276:Parasympatholytics / Q000494:pharmacology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000378:metabolism*; D014697:Ventromedial Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001286:Atropine Derivatives; D010276:Parasympatholytics; D011976:Receptors, Muscarinic; C006649:methylatropine