Hemodynamic responses to electrical stimulation of carotid sinus in conscious rats (1169.15)

Abstract

Carotid sinus (CS) is an important site of arterial baroreceptors and its electrical stimulation has been used to treat patients with resistant hypertension. This study evaluated hemodynamic responses to electrical stimulation of CS in normal conscious rats. Rats (N=5) had left carotid sinus (CS) carefully isolated, equipped with a pair of electrodes and insulated with a layer of Kwik sil. A catheter was introduced into abdominal aorta throughout laparotomy and exteriorized in the back of the neck, together with the CS electrodes. After two days, conscious rats, under continuous recording of AP and HR, had their CS electrically stimulated, during 20 s, with square pulses of 2 ms, 1 mA and 15, 30, 60 and 90 Hz. Rats showed a basal arterial pressure (AP) and heart rate (HR) of 108±3 mmHg and 353±9 bpm. The recorded voltage of the 1 mA pulses allowed the calculation of carotid sinus resistance that ranged from 4.3 to 7.2 kΩ. A fall in mean AP (Δ=19±2, 28±7, 31±4 and 39±4 mmHg) was observed 5‐9 s after the onset of carotid sinus stimulation with 15, 30, 60 and 90 Hz, respectively. A slight and non‐statistically significant fall in HR (9‐35 bpm) was also observed immediately (1‐3 s) after the onset of CS stimulation. In contrast to electrical stimulation of aortic nerve in conscious rats, currently performed in our lab, CS stimulation affected mainly vascular resistance, once only a slight and non‐significant effect was seem in HR.Grant Funding Source: Supported by CAPES, FAPESP, CNPq.