Envolvimento do núcleo pré-óptico mediano (MnPO) na recuperação cardiovascular induzida pela infusão de salina hipertônica em animais submetidos ao choque hemorrágico
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2014-04-16
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Universidade Federal de Goiás
Resumo
In recent decades, several studies have demonstrated that
hyperosmolarity induced by hypertonic saline infusion (HS) it’s a benefit for
hypovolemic hemorrhage treatment. The median preoptic nucleus (MnPO) is
known to receive information from central osmoreceptors and peripheral
afferents about plasma osmolarity changes, reflexively modulating autonomic
and neuroendocrine adjustments, primarily through its projections to the
paraventricular nucleus (PVN). The present study aim to determine MnPO
involvement in cardiovascular recovery induced by HSI in rats subjected to
hemorrhagic shock (HC). Wistar rats (250 - 300 g) were prepared to record
mean arterial pressure (MAP), heart rate (HR), renal blood flow (RBF) and
aortic (ABF). The renal vascular conductance (RVC) and aortic (AVC) were
calculated through the ratio between RBF and ABF with MAP, respectively.
Hemorrhagic shock was induced by blood withdrawal over 10 min until the MAP
reached approximate values of 60 mmHg. The sodium overload by infusion HS
(3 M NaCl, 1.8 ml ∙ kg-1 body mass index) was made 2 min after the
nanoinjection (100 nL) of GABA agonist muscimol (4 mM experimental group 1
- EXP 1 ), α-adrenergic antagonist phentolamine (13 mM ; experimental group 2
- EXP 2) or isotonic saline (NaCl, 0.15 M, control group - CON) in MnPO. This
resulted in HC CON (n=6) MAP reduction (98.4 ± 5.3 to 62.2 ± 1.1 mmHg after
20 min HC, p<0.05), a decrease in RVC (- 59.4 ± 9.2%, 20 min after HC,
p<0.05) and did not alter the AVC (-11.5 ± 10.5%, 20 min after HC) and HR
(387.2 ± 12 to 351.7 ± 13 bpm after 20 min HC). HC promoted in EXP 1 (n=6)
MAP reduction (98 ± 5.4 to 61 ± 0.7 mmHg after 20 min HC, p<0.05), a
decrease in RVC (-64.8 ± 10.9%, 20 min after CH, p<0.05) and CVA (-32.3 ±
4.4%, 20 min after HC, p<0.05) and did not alter HR (389 ± 23.9 ± 17.1 to 360
bpm after 20 min HC). In EXP 2 (n=6) HC resulted in a MAP reduction (102.0 ±
4.2 to 62.0 ± 1.1 mmHg, 20 min after HC, p<0.05), a decrease in CVR (-27.6 ±
5.8% after 20 min HC, p <0.05), CVA (-4.5 ± 4.1% after 20 min HC, p<0.05) and
HR (387 ± 14 to 347 ± 7.4 bpm after 20 min HC). HS infusion enabled MAP
restoration (105.2 ± 3 mmHg, 60 min after infusion of HS, p<0.05), did not alter
HR (400 ± 18.4 bpm, 60 min after infusion of HS) raised the RVC to baseline
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levels (-14.6 ± 14.2%, 60 min after infusion of HS, p<0.05) and reduced AVC (-
27.4 ± 4.3%, 60 min after infusion HS, p<0.05) in CON. HS infusion in EXP 1
was not able to restore MAP (54 ± 3.8 mmHg, 60 min after infusion of HS,
p<0.05) and RVC (- 48.1 ± 9.7%, 60 min after infusion of HS, p<0.05), did not
alter HR (361 ± 15.3 bpm, 60 min after infusion of HS) and was able to promote
an increase in AVC similar to baseline (-23.2 ± 10.6%, 60 min after infusion HS,
p<0.05) levels. In EXP 2, HS infusion enabled MAP restoration (89 ± 3.3
mmHg, 60 min after infusion of HS, p<0.05) but this return to baseline was
delayed and occurred only 50 min after HS infusion (88 ± 3.3 mmHg), HR return
(379 ± 6.5 bpm, 60 min after infusion of HS) and RVC to basal levels (-16.1 ±
8.9%, 60 min after infusion HS, p<0.05) and an increase in AVC 10 min after
HS infusion (20.3 ± 6.4%, p<0.05), which was restored to levels similar to
baseline at registration end (-15.7 ± 6.2%, 60 min after infusion of HS, p<0.05).
Together, the results obtained in this study showed that MnPO plays an
important role in cardiovascular recovery induced by HS infusion in HC cases.
Furthermore, the cardiovascular adjustments involved in this resuscitation seem
to depend partly on adrenergic neurotransmission in this nucleus.
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Citação
AMARAL, N. O. Envolvimento do núcleo pré-óptico mediano (MnPO) na recuperação cardiovascular induzida pela infusão de salina hipertônica em animais submetidos ao choque hemorrágico. 2014. 46 f. Dissertação (Mestrado em Biologia) - Universidade Federal de Goiás, Goiânia, 2014.