Brainstem oxytocinergic modulation of heart rate control in rats: effects of hypertension and exercise training

Autor(es)

Higa-Taniguchi, Keila T. ^[1] ; Felix, Jorge V. C. ^[1] ; Michelini, Lisete C. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Physiol & Biophys, Inst Biomed Sci, BR-05508900 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Experimental Physiology; v. 94, n. 11, p. 1103-1113, NOV 1 2009.
• Citações Web of Science: 20

Resumo

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 (35S-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. (AU)

• Processo FAPESP: 02/00621-0 - Modulação autonômica da resposta taquicárdica ao exercício pela ocitocina endógena no complexo solitário vagal em ratos normotensos e hipertensos
• Beneficiário: Keila Tomoko Higa
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 06/50548-9 - Efeitos do treinamento fisico sobre vias centrais de modulacao autonomica do controle cardiovascular: estudos comparativos na normotensao e hipertensao e efeitos da desnervacao sino-aortica.
• Beneficiário: Lisete Compagno Michelini
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 02/11937-9 - Efeitos beneficos do treinamento fisico sobre o sistema cardiovascular de hipertensos: adaptacoes perifericas e centrais.
• Beneficiário: Lisete Compagno Michelini
• Modalidade de apoio: Auxílio à Pesquisa - Regular