Behavioral Evaluation of Red-eared Slider Turtles (Trachemys scripta elegans) Administered Either Morphine or Butorphanol Following Unilateral Gonadectomy

Abstract

Abstract Pain and analgesia are poorly understood in reptiles, which are commonly maintained in zoological institutions and as laboratory and companion animals. Thus, we developed a behavioral ethogram to evaluate pre-operative and post-operative responses to a thermal stimulus, feeding, movement, and breathing in red-eared slider turtles ( Trachemys scripta elegans ). We hypothesized that opioid drug administration would allow for a more rapid return to pre-operative behavior following a unilateral orchidectomy. The antinociceptive efficacy of morphine (2 mg/kg SC; mu-opioid receptor agonist) and butorphanol (20 mg/kg SC; mixed kappa-opioid receptor agonist and mu-opioid receptor antagonist) were evaluated because of their extensive use as analgesics in veterinary medicine. Compared to sham-saline turtles, surgery-saline turtles exhibited severely depressed feeding and increased movement at 2–8 h postoperation. Butorphanol did not alter feeding, movement, or breathing compared to saline in both sham- and surgery-treated turtles. Morphine depressed feeding and breathing for 1–2 days postoperation, but did not alter movement compared to saline except during the 2–8 h post-operation period. Our results show that pain in red-eared slider turtles is manifested as decreased feeding and increased spontaneous movement. Although turtles returned to normal behavior by 2 days following unilateral orchidectomy, a mu-opioid analgesic drug should be administered for at least 48 h following a surgical procedure.