Anti-hypotensive effect of "Yahom Navakot" in rats with orthostatic hypotension

Abstract

Background and aim: Yahom Navakot (YN), is a Thai traditional medicine, consisting of 54 plants, for treating fainting and dizziness. Thus, YN might relieve orthostatic hypotension (OH) symptoms, but its therapeutic action is unclear. Therefore, this study evaluated YN in OH rats, using a head-up tilt test (HUT).

Experimental procedure: Rats were anesthetized, and OH induced via a 90^oHUT, before and after administering vehicle, a YN powder suspension (10, 100 mg/kg), a YN aqueous extract (100 mg/kg), and midodrine (5 mg/kg). The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), pulse pressure (PP) and heart rate (HR) were determined via the carotid artery. Plasma noradrenaline (NA) was evaluated. YN-induced vasoconstriction of isolated rat aorta rings was determined using organ bath technique.

Results and conclusion: Baseline BP increased with the 100 mg/kg YN powder suspension, the YN aqueous extract or midodrine, while HR decreased, compared with vehicle and control. 90^oHUT rapidly reduced SBP, DPB and MAP, but increased HR, for control and vehicle-treated groups, but BP was steady with the 100 mg/kg YN powder suspension, the YN aqueous extract or midodrine. The 90^oHUT-increase in HR was most pronounced with the 100 mg/kg YN powder suspension (the traditional formulation). This accords with increased plasma NA. YN also induced vasoconstriction in rat aorta via α₁-receptor activation. Thus, the anti-hypotensive action of YN involved a stimulating effect on the heart and blood vessels via sympathetic activation. The results support the traditional use of YN and demonstrated the effectiveness of YN for OH prevention.

Keywords: BP, blood pressure; Blood pressure; DBP, diastolic blood pressure; HR, heart rate; HUT, head-up tilt test; Head-up tilt; MAP, mean arterial blood pressure; NA, noradrenaline; OH, orthostatic hypotension; Orthostatic hypotension; PP, pulse pressure; Quality control; SBP, systolic blood pressure; YN, Yahom Navakot; Yahom Navakot.

Graphical abstract

Fig. 1

Experimental protocol of Yahom Navakot effects on haemodynamic changes in rats with OH using HUT.

Fig. 2

The phytochemical fingerprints of the Yahom Navakot preparation and its components. TLC normal phase visualized under UV 254 nm (A), 366 nm (B), and post-derivertization with anisaldehyde-sulphuric acid (C) and natural product (D) spray reagent.

Fig. 3

The percentage change of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP) and heart rate (HR) from the baseline (0^oHUT), measured at 1, 2, 3, 4min after conducting a 90^oHUT in anesthetized rats orally treated with (A1-4) vehicle (distilled water), (B1-4) 10 mg/kg YN powder suspension (YNS), (C1-4) 100 mg/kg YN powder suspension (YNS), (D1-4) 100 mg/kg YN aqueous extract (YNE) and (E1-4) 5 mg/kg midodrine. A control (no vehicle/drug treatment) HUT experiment was performed before each treatment. Values are expressed as mean ± SEM, n = 6; ∗P < 0.05,∗∗P < 0.01, compared with control (paired t-test).

Fig. 4

Comparison of %change from the baseline of (A) mean arterial blood pressure (MAP) and (B) heart rate (HR) measured at 1, 2, 3, 4min after conducting a 90^oHUT in anesthetized rats orally treated with vehicle (distilled water), 10 mg/kg YN powder suspension (YNS), 100 mg/kg YN powder suspension (YNS), 100 mg/kg YN aqueous extract (YNE) and 5 mg/kg midodrine. A control (no vehicle/drug treatment) HUT experiment was performed before the treatment. Values are expressed as mean ± SEM, n = 6; ∗P < 0.05,∗∗P < 0.01 compared with vehicle and control.

Fig. 5

Changes in mean arterial blood pressure (MAP) at 1min after conducting a 90^oHUT of 5 animal groups orally treated with vehicle (distilled water), 10 mg/kg YN powder suspension (YNS), 100 mg/kg YN powder suspension (YNS), 100 mg/kg YN aqueous extract (YNE) and 5 mg/kg midodrine. A control (no vehicle/drug treatment) HUT experiment was performed before the treatment. Values are expressed as mean ± SEM, n = 6; ∗P < 0.05,∗∗P < 0.01,∗∗∗P < 0.001 compared to control.

Fig. 6

Plasma level of noradrenaline from rats treated with vehicle (distilled water), 10 and 100 mg/kg YN powder suspension (YNS), 100 mg/kg YN aqueous extract (YNE) and 5 mg/kg midodrine. Values are expressed as mean ± SEM, n = 6; ∗∗P < 0.01 compared with vehicle.

Fig. 7

Concentration-response curve for Yahom Navakot (YN) induced vasoconstriction in endothelium-intact (+Endo), endothelium-denuded (-Endo) and endothelium-denuded (-Endo) pre-incubation with prazosin (10⁻⁷ M) rat isolated aorta. Values are expressed as mean ± SEM, n = 6; ∗P < 0.05, ∗∗P < 0.01 compared with control and YN plus prazosin.