Avaliação da dor e do potencial analgésico do tramadol pós-injeção intraovariana de cloreto de cálcio em ratas

Abstract

The use of animals in scientific research is still frequent. There are several situations where there are no in vitro experimental models that can fulfill the research objectives. Many of these studies involve surgical procedures, which ethically require the identification and correct management of pain during the postoperative period, aiming at animal welfare. However, the lack of the verbal component makes the evaluation of pain in animals more difficult and the methods less precise when compared to those employed in humans. However, a non-verbal human pain coding system has been adapted for veterinary medicine. The scale became known as Grimace Scale. In this context, the objective of this study was to identify, through Rat Grimace Scale (RGS), the presence of pain in rats after intraovarian application of calcium chloride in different concentrations, as well as to evaluate the analgesic efficacy of tramadol as rescue analgesia, where necessary. For this, 30 Wistar rats were randomly divided into three groups: Control group (GC, with 0.9% sodium chloride intraovarian application), Group 10 (G10, with 10% calcium chloride intraovarian application) and Group 20 (G20, with intraovarian application of 20% calcium chloride). The animals were induced and maintained anesthetized with isoflurane for the application of the treatments, guided by ultrasound. The time of anesthesia and recovery of the animals was recorded. The evaluation of the presence or absence of pain was performed at 30 min and 1h, 1h30, 2h, 6h, 12h, 24h and 36 hours after anesthesia recovery, by two evaluators trained in the use of the scale and "blind" to the treatments. Animals that presented a final score> 1 at any time of the evaluation received 10 mg / kg of tramadol via SC, as an analgesic rescue. The results showed that the scores obtained were significantly higher in the G20 when compared to the GC from the 1h30 evaluation and 1h in the G10. However, after 12 hours after recovery from anesthesia, there were no differences between the groups until the end of the evaluation. Regarding analgesic rescue, the percentage of rescued animals was significantly higher in G20 (60%) when compared to GC (10%) and G10 (10%). No animal needed more than one ransom. The use of RGS showed to be effective in the identification of pain in rats after calcium chloride injection, evidenced by the differences found between the groups. Also, the 10mg/kg dose of tramadol was effective in controlling pain, regardless of the treatment.