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Brainstem oxytocinergic modulation of heart rate control in rats: effects of hypertension and exercise training
Author(s) -
HigaTaniguchi Keila T.,
Felix Jorge V. C.,
Michelini Lisete C.
Publication year - 2009
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2009.049262
Subject(s) - medicine , endocrinology , oxytocin , heart rate , basal (medicine) , oxytocin receptor , receptor antagonist , blood pressure , antagonist , receptor , insulin
Oxytocinergic brainstem projections participate in the autonomic control of the circulation. We investigated the effects of hypertension and training on cardiovascular parameters after oxytocin (OT) receptor blockade within the nucleus tractus solitarii (NTS) and NTS OT and OT receptor expression. Male spontaneously hypertensive rats (SHR) and Wistar–Kyoto (WKY) rats were trained (55% of maximal exercise capacity) or kept sedentary for 3 months and chronically instrumented (NTS and arterial cannulae). Mean arterial blood pressure (MAP) and heart rate (HR) were measured at rest and during an acute bout of exercise after NTS pretreatment with vehicle or OT antagonist (20 pmol of OT antagonist (200 nl of vehicle) –1 ). Oxytocin and OT receptor were quantified ( 35 S‐oligonucleotide probes, in situ hybridization) in other groups of rats. The SHR exhibited high MAP and HR ( P < 0.05). Exercise training improved treadmill performance and reduced basal HR (on average −11%) in both groups, but did not change basal MAP. Blockade of NTS OT receptor increased exercise tachycardia only in trained groups, with a larger effect on trained WKY rats (+31 ± 9 versus +12 ± 3 beats min −1 in the trained SHR). Hypertension specifically reduced NTS OT receptor mRNA density (–46% versus sedentary WKY rats, P < 0.05); training did not change OT receptor density, but significantly increased OT mRNA expression (+2.5‐fold in trained WKY rats and +15% in trained SHR). Concurrent hypertension‐ and training‐induced plastic (peptide/receptor changes) and functional adjustments (HR changes) of oxytocinergic control support both the elevated basal HR in the SHR group and the slowing of the heart rate (rest and exercise) observed in trained WKY rats and SHR.