Involvement of enhanced cardiac sympathetic afferent reflex in sympathetic activation in early stage of diabetes

Abstract

Cardiac sympathetic afferent reflex (CSAR) is involved in sympathetic activation. The present study was designed to investigate the contribution of enhanced CSAR to sympathetic activation in the early stage of diabetes and the involvement of AT(1) receptors in the paraventricular nucleus (PVN). Diabetes was induced by a single intravenous injection of streptozotocin in rats. Acute experiments were carried out under anesthesia after 3 wk. The CSAR was evaluated by the responses of renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) to epicardial application of capsaicin or bradykinin. Sympathetic activity and CSAR were enhanced in diabetic rats. Plasma norepinephrine and angiotensin II were increased, but the transient receptor potential vanilloid 1 (TRPV1) in the left ventricle wall was not significantly increased in diabetic rats. Pericardial injection of resiniferatoxin to desensitize cardiac afferents or PVN microinjection of lidocaine attenuated the CSAR and decreased the RSNA and MAP in diabetic rats. The AT(1) receptor expression in the PVN increased in diabetic rats. Angiotensin II in the PVN caused greater increases in the RSNA and MAP and enhancement in the CSAR in diabetic rats, which were abolished by the losartan pretreatment. Losartan decreased the RSNA and MAP and attenuated the CSAR in diabetic rats but not in control rats. These results indicate that the CSAR is enhanced in the early stage of diabetic rats, which contributes to the sympathetic activation. AT(1) receptors in the PVN are involved in the enhanced CSAR in diabetic rats.

Angiotensin-(1–7) in Paraventricular Nucleus Modulates Sympathetic Activity and Cardiac Sympathetic Afferent Reflex in Renovascular Hypertensive Rats

“…The nerve signals were amplified with a four channel AC/DC differential amplifier (DP-304, Warner Instruments, Hamden, CT, USA) with a high pass filter at 10 Hz and a low pass filter at 3,000 Hz. The RSNA was integrated at a time constant of 100 ms. At the end of each experiment, the background noise was determined after section of the central end of the nerve and was subtracted from the integrated values of the RSNA [35]. The raw and integrated RSNA, ABP, MAP and HR were simultaneously recorded with a PowerLab data acquisition system (8/35, ADInstruments, Australia).…”

“…The filter paper was removed 1 minute later, and the ventricular surface was rinsed three times with 10 ml of normal saline (37°C). The CSAR was evaluated by the RSNA and MAP responses to the epicardial application of capsaicin [34], [35].…”

Qiliqiangxin Rescues Mouse Cardiac Function by Regulating AGTR1/TRPV1-Mediated Autophagy in STZ-Induced Diabetes Mellitus

“…TRPV1 has recently been shown to have a complex relationship with AGTR1. While some researchers have reported that plasma Ang II is increased in diabetic rats, the expression of TRPV1 in the wall of the left ventricle is not significantly changed [22], and TRPV1 expression in the organum vasculosum laminae terminalis is increased in SHR rats [13], most studies have confirmed that TRPV1 is decreased during ACE1/AGTR1-induced injury or in pressure overload-induced cardiac hypertrophy [23][24][25]. Treatment with captopril, an inhibitor of ACE1, can induce TRPV1 extravasation in the airways [26].…”

Cardiac sympathetic afferent reflex response to intermedin microinjection into paraventricular nucleus is mediated by nitric oxide and γ-amino butyric acid in hypertensive rats

“…The nerve signals were amplified with a high pass filter at 10 Hz and a low pass filter at 3000 Hz by a four-channel AC/DC differential amplifier (DP-304, Warner Instruments, Hamden, CT) and the RSNA was integrated at a time constant of 100 ms. At the end of each experiment, the background noise was determined after section of the central end of the nerve and was subtracted from the integrated values of the RSNA. 36 The raw and integrated RSNA, ABP, MAP, and HR were recorded by a PowerLab data acquisition system (8/35, AD Instruments).…”

“…The filter paper was removed 1 min later, and the ventricular surface was rinsed three times with normal saline (10 mL) at 37 C. The CSAR was evaluated by the RSNA and MAP responses to the epicardial application of capsaicin. 36 The RSNA was expressed as the percent change from the baseline value. RSNA change (%) ¼ (RSNA before ÀRSNA after )/RSNA before  100.…”