Bioelectronic modulation of carotid sinus nerve activity in the rat: a potential therapeutic approach for type 2 diabetes

Figures

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  Fig. 1. Effect of KHFAC modulation of the CSN on cardiorespiratory responses to hypoxia. (a) Cardiorespiratory responses to hypoxia over time with and without KHFAC modulation (period of hypoxia shown by red shaded area). Dark blue, no KHFAC modulation; orange, 20 kHz/1 mA; yellow, 30 kHz/1 mA; purple, 40 kHz/1 mA; green, 50 kHz/1 mA; light blue, 50 kHz/2 mA. Norm., normoxia. (b) Raw data traces of EMG and ECG in normoxic and hypoxic conditions with and without KHFAC modulation. (c) Quantification of respiratory rate change in response to hypoxia with and without KHFAC modulation. Data points represent individual animals and bars represent overall mean respiratory frequency. Circles, baseline; squares, first 30 s of hypoxia response; triangles, last 30 s of hypoxia response. Data represent means ± SEM. One- and two-way ANOVA with Bonferroni multicomparison test: ***p < 0.001 vs baseline within the stimulation group; †††p < 0.001 vs sham

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  Fig. 2. Effect of KHFAC modulation of the CSN on cardiometabolic variables and stress responses in HFHSu-induced type 2 diabetes and its reversibility. (a) Effect of KHFAC on insulin sensitivity assessed by an ITT and expressed as the constant rate for glucose disappearance (KITT) in HFHSu-fed animals. (b) Glucose excursion curves in HFHSu sham animals before diet (black circles), after 15 weeks of diet (grey triangles) and at 24 weeks of diet (black triangles). (c) Glucose excursion curves in HFHSu KHFAC animals before diet (black circles), prior to the initiation of KHFAC (white circles), during 9 weeks of KHFAC (grey squares), and 5 weeks post-KHFAC (white squares). (d) Effect of KHFAC modulation on the AUC obtained through the analysis of glucose excursion curves. (e) Effect of KHFAC modulation on weight gain curves in HFHSu sham (black line) and HFHSu KHFAC (grey line) animals. (f) Effect of KHFAC modulation of the CSN on corticosterone levels in HFHSu-fed animals. Sling cuffs were implanted at week 13 of the HFHSu diet; 2 weeks post-surgery KHFAC stimulation was started. Sham animals represent HFHSu-fed animals with electrical cuff implants but no KHFAC stimulation. (a, d, f)…

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  Fig. 3. Impact of KHFAC modulation of the CSN on ventilatory responses to hypoxia and hypercapnia in age-matched chow-fed control, HFHSu sham and HFHSu KHFAC animals. Ventilatory recordings were performed immediately post-KHFAC and at 1 day, 3 days and 10 days after cessation of KHFAC. Ventilatory recordings were performed in freely moving animals and the protocol consisted of 10 min normoxia (20% O2; white bars), followed by 10 min hypoxia (10% O2; light grey bars), followed by 10 min normoxia, followed by 10 min hypercapnia (20% O2 + 5% CO2; dark grey bars) and finally by 10 min normoxia. Sham animals represent HFHSu animals with electrical cuffs implanted but not submitted to KHFAC. Data are means ± SEM of 4–5 animals. One- and two-way ANOVA with Dunnett’s and Bonferroni multicomparison test: *p < 0.05, **p < 0.01, ***p < 0.001 vs normoxia applied immediately before hypoxic or hypercapnic stimuli; †p < 0.05, †††p < 0.001 vs age-matched control animals

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  Fig. 4. Impact of KHFAC modulation of the CSN on CSN histology. Low and high magnification pictures of 4 μm thick sections stained with haematoxylin–eosin of the left and right carotid bifurcation area isolated from rats in the (a) HFHSu sham group and (b) HFHSu KHFAC group (scale bars, 500 μm and 100 μm for low and high magnification, respectively); black arrows indicate putative CSN sections. Electron microscopy images of the CSN at low and high magnification of the left and right CSN isolated from rats in the (c) HFHSu sham group and (d) HFHSu KHFAC group (scale bars, 2 μm and 500 nm for low and high magnification, respectively). (e) Low magnification image of a 30 μm thick section of the carotid bifurcation area, stained with toluidine blue, isolated from an HFHSu animal implanted with an electrical cuff (scale bar, 500 μm). (f–h) High magnification images of the carotid bifurcation area (scale bars, (f) 200 μm; (g, h), 100 μm); black arrows roughly indicate the position of the implanted cuff as well as fragments of electrodes and silicone; white arrows indicate areas of fibrosis characterised by high density of cells. ECA, external carotid artery; ICA, internal carotid artery; VN,…