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Regulation of sympathetic nerve activity by the nucleus tractus solitarius and rostral ventrolateral medulla is normal in juvenile obese Zucker rats
Author(s) -
Huber Domitila Augusta,
Schreihofer Ann
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.841.4
Adult obese Zucker rats (OZR) have increased sympathetic nerve activity (SNA) and arterial pressure (AP) with reduced GABAergic inhibition of rostral ventrolateral medulla (RVLM) compared to lean Zucker rats (LZR). These OZR also have blunted baroreflexes with a reduced ability of glutamate to activate the nucleus tractus solitarius (NTS). At 7 wks old OZR are overweight and hyperinsulinemic vs. LZR, but have normal AP and baroreflexes. This study examined whether brainstem control of SNA and AP in juvenile OZR is altered prior to the onset of cardiovascular dysfunction. Juvenile male rats (7 wks) were anesthetized with urethane (1.5 g/kg, iv), ventilated, and paralyzed to record splanchnic SNA and AP. Compared to LZR ( n =10), OZR ( n =10) weighed more (309 ± 11 vs. 211 ± 6 g, P <0.001), but had comparable SNA (1.4 ± 0.4 vs. 0.9 ± 0.2 μV) and mean AP (120 ± 3 vs. 118 ± 2 mmHg). In OZR vs. LZR microinjections of glutamate (1 nmol/50 nl) into NTS evoked similar drops in SNA (−73 ± 5 %; −84 ± 4 %). Inhibition of NTS (muscimol; 100 pmol) evoked comparable rises in SNA (80 ± 24 % in OZR; 88 ± 13 % in LZR). Glutamate (1 nmol) into the RVLM evoked equal increases in SNA (91 ± 19 % in OZR; 92 ± 17 % in LZR). Blockade of GABAergic inputs to RVLM (gabazine; 100 pmol) evoked similar rises in SNA (164 ± 39 % in OZR vs 168 ± 34 % in LZR). These results suggest that altered brainstem control of SNA in OZR develops after the onset of obesity. Support: NIH R01HL086759