The Role of Lumbar Sympathetic Nerves in Regulation of Blood Flow to Skeletal Muscle during Anaphylactic Hypotension in Anesthetized Rats

Abstract

During hypovolemic shock, skeletal muscle blood flow could be redistributed to vital organs via vasoconstriction in part evoked by activation of the innervating sympathetic nerve activity. However, it is not well known whether this mechanism operates during anaphylactic shock. We determined the femoral artery blood flow (FBF) and lumbar sympathetic nerve activity (LSNA) mainly regulating the hindquater muscle blood flow during anaphylactic hypotension in anesthetized rats. Anesthetized Sprague-Dawley rats were randomly allocated to the following groups (n = 7/group): (1) non-sensitized, (2) anaphylaxis, (3) anaphylaxis-lumbar sympathectomy (LS) and (4) anaphylaxis-sinoaortic denervation (SAD) groups. Anaphylaxis was induced by an intravenous injection of the ovalbumin antigen to the sensitized rats. The systemic arterial pressure (SAP), heart rate (HR), central venous pressure (CVP), FBF and LSNA were continuously measured. In the anaphylaxis group, LSNA and HR increased, while SAP and FBF decreased after antigen injection. In the anaphylaxis-SAD group, LSNA did not significantly change during the early phase, but the responses of SAP and FBF were similar to those in the anaphylaxis group. In the anaphylaxis-LS group, both FBF and SAP decreased similarly to the anaphylaxis group during anaphylactic hypotension. These results indicated that LSNA increased via baroreceptor reflex, but this sympathoexcitation or LS did not affect antigen-induced decreases in FBF or SAP. Lumbar sympathetic nerves are not involved in regulation of the blood flow to the hindlimb or systemic blood pressure during anaphylactic hypotension in anesthetized rats.

Anaphylactic hypotension causes renal and adrenal sympathoexcitaion and induces c‐fos in the hypothalamus and medulla oblongata

“…General preparations were performed as previously described (Song et al., ; Sun et al., ; Tanida et al., ; Tanida et al., ). Briefly, under pentobarbital sodium anaesthesia (50 mg kg −1 , i.p.…”

“…To perform sinoaortic denervation (SAD) (Song et al., ; Sun et al., ) in rats in which adrenal SNA was measured, after the neurovascular trunk in the neck was exposed, the carotid sinus, aortic depressor and recurrent laryngeal nerves were sectioned bilaterally. Successful SAD was confirmed by the absence of reflex increases in HR and adrenal SNA in response to the hypotension induced by SNP (Figure d, e).…”

“…General preparations were performed as previously described (Song et al, 2016;Sun et al, 2014;Tanida et al, 2007;Tanida et al, 2015).…”

“…Anaphylactic shock‐accompanied hypotension is potentially life threatening. In our previous experiments, blood pressure in rats sensitized by subcutaneous injections of an emulsion made by mixing equal volumes of complete Freund's adjuvant with ovalbumin dissolved in physiological saline decreased after intravenous injection of antigen (Wang, Tanida, Shibamoto, & Kurata, ; Sun et al., ; Wang et al., ; Song et al., ).…”

“…Experimental Physiology c 2018 The Physiological Society The sympathetic nervous system serves as a defence system against anaphylactic shock (Koyama et al, 1990;Song et al, 2016;Sun et al, 2014;Wang et al, 2013). Although efferent sympathetic nerve activity (SNA) to the kidney and hindlimb (Song et al, 2016) increased during anaphylactic hypotension in anaesthetized rats, the SNA in the liver did not change (Wang et al, 2013). These results indicated regional differences in the SNA response to anaphylactic hypotension.…”