Effects of Anesthetics on the Renal Sympathetic Response to Anaphylactic Hypotension in Rats

Abstract

The autonomic nervous system plays an important role in rat anaphylactic hypotension. It is well known that sympathetic nerve activity and cardiovascular function are affected by anesthetics. However, the effects of different types of anesthesia on the efferent renal sympathetic nerve activity (RSNA) during anaphylactic hypotension remain unknown. Therefore, we determined the renal sympathetic responses to anaphylactic hypotension in anesthetized and conscious rats and the roles of baroreceptors in these responses. Sprague-Dawley rats were randomly allocated to anesthetic groups that were given pentobarbital, urethane, or ketamine-xylazine and to a conscious group. The rats were sensitized using subcutaneously injected ovalbumin. The systemic arterial pressure (SAP), RSNA and heart rate (HR) were measured. The effects of sinoaortic baroreceptor denervation on RSNA during anaphylaxis were determined in pentobarbital-anesthetized and conscious rats. In all of the sensitized rats, the RSNA increased and SAP decreased after antigen injection. At the early phase within 35 min of the antigen injection, the antigen-induced sympathoexcitation in the conscious rats was significantly greater than that in the anesthetized rats. Anaphylactic hypotension was attenuated in the conscious rats compared to the anesthetized rats. The anesthetic-induced suppression of SAP and RSNA was greater in the order ketamine-xylazine >urethane = pentobarbital. Indeed, in the rats treated with ketamine-xylazine, RSNA did not increase until 40 min, and SAP remained at low levels after the antigen injection. The baroreceptor reflex, as evaluated by increases in RSNA and HR in response to the decrease in SAP induced by sodium nitroprusside (SNP), was suppressed in the anesthetized rats compared with the conscious rats. Consistent with this finding, baroreceptor denervation attenuated the excitatory responses of RSNA to anaphylaxis in the conscious rats but not in the pentobarbital-anesthetized rats. RSNA was increased markedly in conscious rats during anaphylactic hypotension. Anesthetics attenuated this antigen-induced renal sympathoexcitation through the suppression of baroreceptor function.

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

“…However, this did not occur in the current study. The sympathetic response to anaphylaxis was attenuated in anaesthetized rats, compared to conscious rats (Sun et al., ). Thus, anaesthesia might have influenced the BAT‐SNA response to anaphylactic hypotension.…”

“…Thus, anaphylactic hypotension may affect the medullary neural pathway containing GABA neurons in the NTS and C1 neurons in the RVLM to enhance renal and adrenal SNA. Notably, c‐fos immunoreactivity was increased in the RVLM and caudal NTS by anaphylactic hypotension in SAD rats, with renal (Sun et al., ) and adrenal sympathoexcitation. Thus, these lines of evidence suggested that anaphylaxis in the anaesthetized rats activated the medullary areas, including the caudal NTS and RVLM, independently of baroreceptors, which resulted in sympathoexcitation.…”

“…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).…”

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