Somayyeh Naderi - PhD Candidate, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Esmaeal Tamaddonfard - Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Saeid Nafisi - Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Farhad Soltanalinejad-Taghiabad - Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran

Thymoquinone (TQ) is the main biologically active substance of Nigella sativa (black seeds). It has anti-cancer, anti-inflammatory, anti-diabetic, anti-oxidative and anti-nociceptive properties. This study was aimed to explore the effect of TQ on acetic acid-induced visceral nociception. The central mechanisms of the effect of TQ were investigated using cannabinergic (AM۲۵۱) and α۲-adrenergic (yohimbine [Yoh]) antagonists. The lateral ventricle of the brain was cannulated for intracerebroventricular (ICV) injections. Visceral nociception was induced by intra-peritoneal (IP) injection of acetic acid (۱.۰۰% in a volume of ۱.۰۰ mL). Measuring the latency time to the first writhing appearance and counting the number of writhing in ۵-min intervals for a period of ۶۰ min were performed. Locomotor activity was determined using an open-field test. Oral administration (PO) of ۲.۵۰ and ۱۰.۰۰ mg kg-۱ TQ increased the latency time to the first writhing appearance and decreased the number of writhing. The AM۲۵۱ (۵.۰۰ µg per rat; ICV) and Yoh (۵.۰۰ µg per rat; ICV) partially prevented TQ (۱۰.۰۰ mg kg-۱; PO)-induced anti-nociception. Locomotor activity was not altered by these treatments. The results of the present study showed that TQ had the ability to reduce visceral nociception caused by IP injection of acetic acid. The central mechanisms of this action of TQ might be partially mediated by cannabinergic and α۲-adrenegic receptors.

Cannabinergic receptor, Rats, Thymoquinone, visceral nociception, Yohimbine