The Effect of Systemic Administration of Monoterpenes on Visceral Pain in an Animal Model

Abstract

Introduction: Pain is one of the primary and fundamental issues associated with various diseases that every individual will encounter throughout their lifetime. Non-steroidal anti-inflammatory drugs (NSAIDs) and opioids are commonly used for pain control, but they have significant side effects. The current study aimed to evaluate the effect of systemic administration of monoterpenes on visceral pain in an animal model. Materials and methods: In this experimental study, 30 male albino rats weighing approximately 21 to 25 grams were used. The rats were randomly divided into three groups of 10. The control group did not receive any drug, while the first treatment group received d-limonene orally at a dose of 10 milligrams per kilogram, known as a monoterpene compound. The second treatment group received tramadol orally at a dose of 20 milligrams per kilogram. To assess the effects of monoterpenes on colonic pain, intraperitoneal injection of 6% acetic acid (4 mg/kg) was used, and the number of reflex contractions, which could be easily distinguishable and lasted for several seconds, was observed and counted for 90 minutes. Data were collected and averaged every 5 minutes and then subjected to initial statistical analysis. Results: A significant difference in terms of visceral pain was observed between these two groups. The rats in the first treatment group that received limonene perceived significantly less visceral pain than those in the control group. The findings indicated a significant difference between treatment groups 1 and 2, meaning that tramadol creates a greater analgesic effect. Conclusion: This finding suggests that monoterpenes cannot produce the same level of analgesic effects on visceral pain as opioids.