Non-Invasive Ultrasound Modulation of Solitary Tract Nucleus Exerts a Sustainable Antihypertensive Effect in Spontaneously Hypertensive Rats

Fangyuan Cao, Jingjing Zhang, Dapeng Li, Mengke Wang, Chunhao Lai, Tianqi Xu, Ayache Bouakaz, Pengyu Ren, Mingxi Wan, Jie Han, Siyuan Zhang

IEEE Transactions on Biomedical Engineering 2023, 70, 1869-1878 · 10.1109/tbme.2022.3231343

rodentotherautonomic physiologyhistology molecular

Abstract

Objective We applied the method of non-invasive ultrasound (US) neuromodulation to regulate blood pressure (BP) by stimulating the solitary tract nucleus (NTS) of spontaneously hypertensive rats (SHRs). Methods The rats were exposed to US stimulation for 20 mins every day for two months. Morphology and function of the hypertensive target organs (heart and kidney) were then examined by echocardiography and immunohistochemical staining. C-fos immunofluorescence assays were used to evaluate neuronal activity in the US stimulated areas and to explore related neural pathways. Moreover, the effects of US stimulation on biochemical indicators angiotensinII (ANGII), aldosterone (Aldo), endothelin-1 (ET-1), atrial natriuretic factor (ANF), cortisol (Cor) in SHRs were detected. In addition, HE, TUNEL, and Nissl staining were performed to evaluate the safety of long-term transcranial US stimulation. Results After two months of US stimulation, systolic blood pressure (SBP) decreased from 170 ± 1.1 mmHg to 158 ± 1.8 mmHg, p Conclusion US stimulation of the NTS could significantly lower BP in SHRs. Significance Non-invasive transcranial US stimulation acting on the NTS might be a potential therapeutic intervention due to its efficacy and safety.

Abstract via europepmc.

Speciesrat (spontaneously hypertensive rat, SHR; Wistar-Kyoto, WKY)

Subjects7, 7swept animals

Sessions per subjectnot reported

Randomisedyes

Blindingnot reported

Sham / controlactive control site

Auditory controlnot reported

Readout timingoffline

Anaesthesiaanaesthetised

Readoutsautonomic physiology, histology molecular — tail-cuff blood pressure measurement; echocardiography (LVEDWT, LVESWT, heart rate); c-fos immunofluorescence; HE/Masson/TUNEL/Nissl staining; ELISA for ANGII, aldosterone, ET-1, ANF, cortisol

Direction of effectexcitatoryUS stimulation of the NTS increased c-fos expression in the NTS, vlPAG, and CVLM, and produced a sustained antihypertensive effect (systolic BP from 170±1.1 to 158±1.8 mmHg over two months) with reduced plasma ANGII, aldosterone, and cortisol, and attenuated cardiac and renal hypertensive damage.

Adverse eventsnone observedHE, TUNEL, and Nissl staining showed no apparent morphological changes, tissue damage, or neuronal apoptosis in stimulated brain regions after two months of transcranial US stimulation.

Exposures

Exposure 1: Transcranial US stimulation of the nucleus tractus solitarius (NTS)

Target: nucleus tractus solitarius — “solitary tract nucleus (NTS)”
Device: not reported

Pulse timing
Waveform	pulsed
Fundamental frequency (kHz)	620	✓✓✓
Pulse duration (ms)	2	✓✓✓
Pulse repetition frequency (Hz)	250	✓✓✓
Duty cycle (%)	not reportedpulse duration × PRF gives 50%	⚑
Sonication duration (s)	0.2	✓✓✓

Pressure and intensity, by domain
Free-field pressure (kPa)	not reported	⚑
Free-field Isppa (W/cm²)	not reported
Free-field Ispta (W/cm²)	not reported
In-situ estimate	measurementsingle value
In-situ pressure (kPa)	320	✓✓✓
In-situ Isppa (W/cm²)	3.28	✓✓✓
In-situ Ispta (W/cm²)	1.64	✓✓✓

Protocol, in the paper’s words

US-NTS and Sham (motor-cortex target) groups were exposed to US stimulation every afternoon for the first month, then every two days for the second month, for a total of two months (20 min per daily session per the abstract). Each sonication used pulse duration 2 ms, PRF 250 Hz, total sonication duration 200 ms, and pulse interval (PI) 5 s.

Flags from extraction

n_subjects — Total of 28 rats (4 groups x n=7) were enrolled, but only the US-NTS and Sham groups (7+7=14) actually received ultrasound; the SHR and WKY groups were unstimulated controls.
n_sessions_per_subject — Stimulation was given daily for the first month then every two days for the second month; the paper does not state a single total session count per animal.
exposures[0].timing.duty_cycle_pct — Duty cycle is not stated directly; it would require computing from pulse duration (2 ms) and PRF (250 Hz), which the extraction rules prohibit.
exposures[0].free_field.pressure_kpa — Only an in-situ (through-skull) acoustic measurement is reported; no free-field/water-only value is given in the text.