Author:
Wanner S P,Guimarães J B,Pires W,La Guardia R B,Haibara A S,Marubayashi U,Coimbra C C,Lima N R V
Abstract
The effects of blocking ventromedial hypothalamic nucleus (VMH)
muscarinic cholinoceptors on cardiovascular responses were
investigated in running rats. Animals were anesthetized with
pentobarbital sodium and fitted with bilateral cannulae into the
VMH. After recovering from surgery, the rats were familiarized to
running on a treadmill. The animals then had a polyethylene
catheter implanted into the left carotid artery to measure blood
pressure. Tail skin temperature (Ttail), heart rate, and systolic,
diastolic and mean arterial pressure were measured after
bilateral injections of 0.2 μl of 5 × 10−9
mol methylatropine or
0.15 M NaCl solution into the hypothalamus. Cholinergic blockade
of the VMH reduced time to fatigue by 31% and modified the
temporal profile of cardiovascular and Ttail adjustments without
altering their maximal responses. Mean arterial pressure peak
was achieved earlier in methylatropine-treated rats, which also
showed a 2-min delay in induction of tail skin vasodilation,
suggesting a higher sympathetic tonus to peripheral vessels. In
conclusion, muscarinic cholinoceptors within the VMH are
involved in a neuronal pathway that controls exercise-induced
cardiovascular adjustments. Furthermore, blocking of cholinergic
transmission increases sympathetic outflow during the initial
minutes of exercise, and this higher sympathetic activity may be
responsible for the decreased performance.
Publisher
Institute of Physiology of the Czech Academy of Sciences
Subject
General Medicine,Physiology
Cited by
15 articles.
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