Unveiling the anti-inflammatory and antinociceptive effects of limonene in two models of carrageenan-induced inflammation and formalin-induced pain: role of l-arginine/nitric oxide/cGMP/KATP channel signaling pathways, opioidergic, and benzodiazepine receptors.

Pain and inflammation are critical and complex biological responses to tissue damage or disease, which significantly impair life quality. The complex pathophysiological mechanisms highlight the necessity for multitarget therapeutic interventions. Limonene, a monoterpene, has shown promising antioxidant and anti-inflammatory properties. This study aimed to elucidate the anti-inflammatory and antinociceptive role of limonene and related mechanisms of action in two animal models. Two models of carrageenan-induced inflammation in rats and formalin-induced pain in mice were employed. In the carrageenan model of inflammation, 30 male Wistar rats were used, including control, diclofenac, and three doses of limonene (5, 10, and 15 mg/kg). The groups followed for 4 h, and paw edema was evaluated using a plethysmometer. In the formalin model of pain, 114 male mice were divided into 19 groups including control, and diclofenac, limonene (5, 10, and 15 mg/kg), l-arginine, N(gamma)-nitro-l-arginine methyl ester (L-NAME), S-nitroso-N-acetylpenicillamine (SNAP), sildenafil, glibenclamide, naloxone, and flumazenil, individually and before the most effective doses of limonene, all intraperitoneal. After the limonene administration, a formalin test was conducted to evaluate pain responses in the mice during both the early neurogenic and late inflammatory phases. The findings indicated that a 10 mg/kg dose of limonene produced the most significant antinociceptive and anti-inflammatory effects. Furthermore, while L-NAME, glibenclamide, naloxone, and flumazenil diminished the antinociceptive properties of limonene, l-arginine, SNAP, and sildenafil increased its effectiveness. This study demonstrated that limonene exhibited antinociceptive and anti-inflammatory properties, mediated through the l-arginine/nitric oxide (NO)/cyclic GMP (cGMP)/ATP-sensitive potassium channel (KATP) signaling pathways, opioidergic, and benzodiazepine receptors.