Open AccessPhysical Exercise-Induced Cardiovascular Adjustments Are Modulated by Muscarinic Cholinoceptors within the Ventromedial Hypothalamic Nucleus
Author(s) -
Samuel Penna Wanner,
Juliana B. Guimarães,
Washington Pires,
Roberta Borges La Guardia,
Andréa Siqueira Haibara,
Umeko Marubayashi,
Cândido Celso Coimbra,
Nilo Resende Viana Lima
Publication year - 2010
Publication title -
physiological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.647
H-Index - 70
eISSN - 1802-9973
pISSN - 0862-8408
DOI - 10.33549/physiolres.931649
Subject(s) - medicine , endocrinology , muscarinic acetylcholine receptor , ventromedial nucleus of the hypothalamus , blood pressure , hypothalamus , heart rate , cholinergic , acetylcholine , anesthesia , receptor
The effects of blocking ventromedial hypothalamic nucleus (VMH)muscarinic cholinoceptors on cardiovascular responses wereinvestigated in running rats. Animals were anesthetized withpentobarbital sodium and fitted with bilateral cannulae into theVMH. After recovering from surgery, the rats were familiarized torunning on a treadmill. The animals then had a polyethylenecatheter implanted into the left carotid artery to measure bloodpressure. Tail skin temperature (Ttail), heart rate, and systolic,diastolic and mean arterial pressure were measured afterbilateral injections of 0.2 μl of 5 × 10−9 mol methylatropine or0.15 M NaCl solution into the hypothalamus. Cholinergic blockadeof the VMH reduced time to fatigue by 31% and modified thetemporal profile of cardiovascular and Ttail adjustments withoutaltering their maximal responses. Mean arterial pressure peakwas achieved earlier in methylatropine-treated rats, which alsoshowed a 2-min delay in induction of tail skin vasodilation,suggesting a higher sympathetic tonus to peripheral vessels. Inconclusion, muscarinic cholinoceptors within the VMH areinvolved in a neuronal pathway that controls exercise-inducedcardiovascular adjustments. Furthermore, blocking of cholinergictransmission increases sympathetic outflow during the initialminutes of exercise, and this higher sympathetic activity may beresponsible for the decreased performance.