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.
- MeSH
- deriváty atropinu farmakologie MeSH
- kondiční příprava zvířat fyziologie MeSH
- krevní tlak fyziologie účinky léků MeSH
- krysa rodu rattus MeSH
- nucleus ventromedialis hypothalami fyziologie účinky léků MeSH
- ocas MeSH
- parasympatolytika farmakologie MeSH
- potkani Wistar MeSH
- receptory muskarinové fyziologie MeSH
- srdeční frekvence fyziologie účinky léků MeSH
- sympatický nervový systém fyziologie MeSH
- teplota kůže fyziologie účinky léků MeSH
- vazodilatace fyziologie účinky léků MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
