Endogenous hydrogen peroxide in the hypothalamic paraventricular nucleus regulates sympathetic nerve activity responses to L-glutamate.
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2012
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Resumo
Endogenous hydrogen
peroxide in the hypothalamic paraventricular nucleus regulates
sympathetic nerve activity responses to L-glutamate. J Appl
Physiol 113: 1423–1431, 2012. First published September 13,
2012; doi:10.1152/japplphysiol.00912.2012.—The hypothalamic
paraventricular nucleus (PVN) is important for maintenance of sympathetic
nerve activity (SNA) and cardiovascular function. PVNmediated
increases of SNA often involve the excitatory amino acid
L-glutamate (L-glu), whose actions can be positively and negatively
modulated by a variety of factors, including reactive oxygen species.
Here, we determined modulatory effects of the highly diffusible
reactive oxygen species hydrogen peroxide (H2O2) on responses to
PVN L-glu. Renal SNA (RSNA), arterial blood pressure, and heart
rate were recorded in anesthetized rats. L-Glu (0.2 nmol in 100 nl)
microinjected unilaterally into PVN increased RSNA (P 0.05),
without affecting mean arterial blood pressure or heart rate. Effects of
endogenously generated H2O2 were determined by comparing responses
to PVN L-glu before and after PVN injection of the catalase
inhibitor 3-amino-1,2,4-triazole (ATZ; 100 nmol/200 nl, n 5). ATZ
alone was without effect on recorded variables, but attenuated the
increase of RSNA elicited by PVN L-glu (P 0.05). PVN injection
of exogenous H2O2 (5 nmol in 100 nl, n 4) and vehicle (artificial
cerebrospinal fluid) were without affect, but H2O2, like ATZ, attenuated
the increase of RSNA to PVN L-glu (P 0.05). Tonic effects
of endogenous H2O2 were determined by PVN injection of polyethylene
glycol-catalase (1.0 IU in 200 nl, n 5). Whereas polyethylene
glycol-catalase alone was without effect, increases of RSNA to
subsequent PVN injection of L-glu were increased (P 0.05). From
these data, we conclude that PVN H2O2 tonically, but submaximally,
suppresses RSNA responses to L-glu, supporting the idea that a
change of H2O2 availability within PVN could influence SNA regulation
under physiological and/or disease conditions.
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Palavras-chave
Glutamatergic transmission, Arterial blood pressure, Reactive oxygen species, Catalase, Superoxide dismutase
Citação
CARDOSO, L. M.; COLOMBARI, E.; TONEY, G. M. Endogenous hydrogen peroxide in the hypothalamic paraventricular nucleus regulates sympathetic nerve activity responses to L-glutamate. Journal of Applied Physiology, v. 113, p. 1423-1431, 2012. Disponível em: <https://www.physiology.org/doi/full/10.1152/japplphysiol.00912.2012>. Acesso em: 19 fev. 2017.