An improved strategy for evaluating the extent of chronic arterial baroreceptor denervation in conscious rats

There is no index or criterion of aortic barodenervation, nor can we differentiate among rats that have suffered chronic sham, aortic or sino-aortic denervation. The objective of this study was to develop a procedure to generate at least one quantitative, reproducible and validated index that precisely evaluates the extent of chronic arterial barodenervation performed in conscious rats. Data from 79 conscious male Wistar rats of about 65-70 days of age with diverse extents of chronic arterial barodenervation and used in previous experiments were reanalyzed. The mean arterial pressure (MAP) and the heart rate (HR) of all rats were measured systematically before (over 1 h) and after three consecutive iv bolus injections of phenylephrine (PHE) and sodium nitroprusside (SNP). Four expressions of the effectiveness of barodenervation (MAP lability, PHE ratio, SNP ratio, and SNP-PHE slope) were assessed with linear fixed models, three-level average variance, average separation among levels, outlier box plot analysis, and overlapping graphic analysis. The analysis indicated that a) neither MAP lability nor SNP-PHE slope was affected by the level of chronic sodium intake; b) even though the Box-Cox transformations of both MAP lability [transformed lability index (TLI)] and SNP-PHE slope [transformed general sensitivity index (TGSI), {((3-(ΔHRSNP-ΔHRPHE/ΔMAPSNP-ΔMAPPHE))-0.4-1)/-0.04597}] could be two promising indexes, TGSI proved to be the best index; c) TLI and TGSI were not freely interchangeable indexes for this purpose. TGSI ranges that permit differentiation between sham (10.09 to 11.46), aortic (8.40 to 9.94) and sino-aortic (7.68 to 8.24) barodenervated conscious rats were defined.

Effect of carotid and aortic baroreceptors on cardiopulmonary reflex: the role of autonomic function

We determined the sympathetic and parasympathetic control of heart rate (HR) and the sensitivity of the cardiopulmonary receptors after selective carotid and aortic denervation. We also investigated the participation of the autonomic nervous system in the Bezold-Jarish reflex after selective removal of aortic and carotid baroreceptors. Male Wistar rats (220-270 g) were divided into three groups: control (CG, N = 8), aortic denervation (AG, N = 5) and carotid denervation (CAG, N = 9). AG animals presented increased arterial pressure (12 percent) and HR (11 percent) compared with CG, while CAG animals presented a reduction in arterial pressure (16 percent) and unchanged HR compared with CG. The sequential blockade of autonomic effects by atropine and propranolol indicated a reduction in vagal function in CAG (a 50 and 62 percent reduction in vagal effect and tonus, respectively) while AG showed an increase of more than 100 percent in sympathetic control of HR. The Bezold-Jarish reflex was evaluated using serotonin, which induced increased bradycardia and hypotension in AG and CAG, suggesting that the sensitivity of the cardiopulmonary reflex is augmented after selective denervation. Atropine administration abolished the bradycardic responses induced by serotonin in all groups; however, the hypotensive response was still increased in AG. Although the responses after atropine were lower than the responses before the drug, indicating a reduction in vagal outflow after selective denervation, our data suggest that both denervation procedures are associated with an increase in sympathetic modulation of the vessels, indicating that the sensitivity of the cardiopulmonary receptors was modulated by baroreceptor fibers.

In vivo detection of vascular systolic/relaxant function in sino-aortic denervated rats / 中国药理学通报

AIM: To investigate the changes of vascular systiolic/relaxant function in sino-aortic denervated rats. METHODS: Male Sprague-Dawley rats were underwent sino-aortic denervation (SAD). The sinoaortic denervated (SAD) rats were adopted as a model of arterial baroreflex deficit. SAD, isolated aortic-denervated (AD) and isolated sinus-denervated (SD) rats were instrumented chronically to record blood pressure (BP), heart rate (HR), BP variability (BPV), HR variability (HRV), arterial baroreflex function control of heart period (ABR-HP) and BP (ABR-BP). The vascular maximum contractile/relaxant function was determined through cumulative venous injection of phenylephrine (SBPmax) and nitroprusside(DBPmin) both after ganglionic blokade. RESULTS: Acute SAD(1 week after operation) caused hypertension and tachycardia in rats. Eighteen weeks after operation, BP and HR values in SAD and SD rats were not different from those in sham-operated rats, but AD rats were hypertensive compared with control group. Though the 24 h mean BP values of chronic (18 weeks after operation) SAD rats was not different from those in the sham-operated rats, 24 h BPV of SAD rats was significantly higher when compared with sham-operated rats. ABR function in the acute SAD rats was significantly decreased when compared with sham-operated rats, whereas in chronic SAD rats, both ABR-HP and ABR-BP were higher than those in acute SAD rats, but were still significantly lower than those in control groups. 18 weeks after operation, ABR function in SAD and AD rats were significantly decreased when compared with those in SD and control groups. SBPmax after phenylephrine and DBPmin after nitroprusside were significantly higher in SAD, AD and SD rats than in control group. ABR function was negatively correlated to DBPmin(r = -0.677 for ABR-HP, and r = -0.681 for ABR-BP; P<0.001) and SBPmax(r = -0.614 for. ABR-HP, and r = -0.545 for ABR-BP; P< 0.001) in the whole group of the denervated rats (n = 44). ABR function of the sino-aortic denervated rats was negatively related to the 24 h BPV. CONCLUSION: Remarkable changes of vascular systolic/ relaxant dysfunction are observe in sino-aortic denervated rats 18 weeks after operation, and this effect is closely relate to the decreased ABR function and increase 24 h BPV.

In vivo detection of vascular systolic/relaxant function in sino-aortic denervated rats / 中国药理学通报

AIM To investigate the changes of vascular systiolic/relaxant function in sino-aortic denervated rats. METHODS Male Sprague-Dawley rats were underwent sino-aortic denervation (SAD). The sinoaortic denervated (SAD) rats were adopted as a model of arterial baroreflex deficit. SAD, isolated aortic-denervated (AD) and isolated sinus-denervated (SD) rats were instrumented chronically to record blood pressure (BP), heart rate (HR), BP variability (BPV), HR variability (HRV), arterial baroreflex function control of heart period (ABR-HP) and BP (ABR-BP). The vascular maximum contractile/relaxant function was determined through cumulative venous injection of phenylephrine (SBP max ) and nitroprusside(DBP min ) both after ganglionic blokade. RESULTS Acute SAD(1 week after operation) caused hypertension and tachycardia in rats. Eighteen weeks after operation, BP and HR values in SAD and SD rats were not different from those in sham-operated rats, but AD rats were hypertensive compared with control group. Though the 24 h mean BP values of chronic (18 weeks after operation) SAD rats was not different from those in the sham-operated rats, 24 h BPV of SAD rats was significantly higher when compared with sham-operated rats. ABR function in the acute SAD rats was significantly decreased when compared with sham-operated rats, whereas in chronic SAD rats, both ABR-HP and ABR-BP were higher than those in acute SAD rats, but were still significantly lower than those in control groups. 18 weeks after operation, ABR function in SAD and AD rats were significantly decreased when compared with those in SD and control groups. SBP max after phenylephrine and DBP min after nitroprusside were significantly higher in SAD, AD and SD rats than in control group. ABR function was negatively correlated to DBP min ( r =-0.677 for ABR-HP, and r =-0.681 for ABR-BP; P