Hargreaves does not evaluate nociception following a surgical laparotomy in Xenopus leavis frogs

The present study was performed to determine the effectiveness of the Hargreaves test for the evaluation of nociception in frogs, more precisely to determine if cutaneous thresholds to a radiant heat stimulus would increase with analgesics following an abdominal laparotomy performed under general anaesthesia. Non breeding female Xenopus leavis frogs (3 groups (non-anaesthetized, anaesthetized with tricaine methanesulfonate (MS222), with or without an abdominal laparotomy) were used to evaluate the effectiveness of the Hargreaves test. Cutaneous thresholds were evaluated at baseline and following anaesthetic recovery (over 8 h) at six different body locations. Increased reaction times were observed in the gular area only at 1 h post-recovery following a MS222 bath immersion in frogs with (p < 0.02) and without the abdominal laparotomy (p < 0.002). In conclusion, the Hargreaves test does not provide an adequate test to evaluate nociception induced by an abdominal laparotomy and consequently cannot be used to evaluate analgesics in X. leavis frogs.