HYPOTENSIVE ACTIVITY OF THYMOQUINONE IN NORMOTENSIVE RATS AND ITS RECEPTOR MECHANISMS
Objective: The objectives of the current study were to confirm the blood pressure lowering effect of thymoquinone (TQ) and to investigate its mechanism through muscarinic and Î²-adrenergic receptors.
Methods: Mean arterial blood pressure (MAP) was recorded using the non-invasive blood pressure tail-cuff technique. A dose-response relationship was obtained after using 3 TQ doses (2.5, 5 and 10 mg/kg) intraperitoneally to 3 different groups (n =5) of adult rats under pentobarbital anesthesia. MAP was then measured for another 2 animal groups pretreated either with atropine (P-at) or propranolol (P-pro) followed by 10 mg/kg TQ.
Results: TQ produced a significant dose-dependent blood pressure and heart rate lowering effect. TQ-induced MAP reduction was significantly less pronounced in P-at (12Â±2.8 mmHg) than non-pretreated group (29Â±3.2 mmHg) with P<0.01. Conversely, TQ-induced MAP reduction in P-pro (28Â±3.4 mmHg) did not demonstrate a significant difference from the non-pretreated group (29Â±3.2 mmHg) with P>0.05.
Conclusion: This study confirms the dose-related hypotensive effect of TQ and provides an evidence for the traditional use of Nigella sativa for the treatment of hypertension. The mechanism of TQ-induced hypotension involves at least in part activation of vascular muscarinic receptors, but not Î²-adrenergic receptors.
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