title: Tachycardia in response to remote capsaicin injection as a model for nociception in the ball python (Python regius).
abstract: OBJECTIVE
  To quantify the effect of subcutaneous (SC) capsaicin injection on heart rate (HR) in ball pythons (Python regius) and to assess the efficacy of two opioids (morphine and butorphanol) in modifying this response.
  
  
  METHODS
  Prospective, randomized, unmatched study.
  
  
  METHODS
  Eleven mixed-sex, captive-bred ball pythons.
  
  
  METHODS
  Snakes were randomly assigned to three groups (n = 6) by intramuscular premedication: 1) control: saline (0.9 mL); 2) morphine (10 mg kg(-1) ); and 3) butorphanol (10 mg kg(-1) ). Three snakes were tested twice and another two were tested three times in different treatments administered 1 month apart. Under isoflurane anaesthesia, snakes were instrumented with SC electrocardiogram (ECG) electrodes and an SC catheter for remote stimulus delivery. After recovery from anaesthesia, all snakes, in visual and audial isolation from the experimenter, received a sham stimulus of saline (0.4 mL) via the SC catheter. A nociceptive stimulus of SC capsaicin (3 mg in 0.2 mL saline with 7% Tween 80) was then applied by catheter at 7 hours after premedication. In a subset (n = 3), two sham injections (saline 0.2 mL) preceded the capsaicin treatment. HR was recorded via ECG, and changes in HR (ΔHR) from baseline were calculated for all stimulations.
  
  
  RESULTS
  Capsaicin injection was associated with a significant increase in HR [peak ΔHR: saline group: 8.8 ± 7.1 beats minute(-1) ; capsaicin group: 21.1 ± 5.8 beats minute(-1) (p = 0.0055)] and integrated ΔHR as a function of time. The administration of morphine or butorphanol 7 hours prior to nociception failed to significantly reduce the peak and integrated ΔHR. Butorphanol caused marked, long-lasting sedation as assessed by muscle tone.
  
  
  CONCLUSIONS
  The HR response to an SC capsaicin injection can serve as a nociceptive model in P. regius. Morphine and butorphanol administration did not reduce HR response to capsaicin stimulation but produced significantly different effects on pre-stimulation HR and sedation.
authors.affiliation: Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
authors.forename: Catherine J A
authors.identifier: http://orcid.org/0000-0002-4839-6134
authors.initials: CJ
authors.lastname: Williams
authors.affiliation: Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: James
authors.affiliation: Centre for Zoo and Wild Animal Health, Copenhagen Zoo, Copenhagen, Denmark.
authors.forename: Mads F
authors.initials: MF
authors.lastname: Bertelsen
authors.affiliation: Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wang
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D017821:Boidae / Q000502:physiology*; D002077:Butorphanol / Q000494:pharmacology*; D002211:Capsaicin / Q000008:administration & dosage / Q000009:adverse effects*; D004195:Disease Models, Animal; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D009020:Morphine / Q000494:pharmacology*; D059225:Nociception / Q000187:drug effects* / Q000502:physiology; D011446:Prospective Studies; D018689:Sensory System Agents / Q000008:administration & dosage / Q000009:adverse effects*; D013610:Tachycardia / Q000139:chemically induced / Q000662:veterinary*
chemical_list: D000701:Analgesics, Opioid; D018689:Sensory System Agents; D009020:Morphine; D002077:Butorphanol; D002211:Capsaicin
keywords: analgesia; butorphanol; capsaicin; morphine; reptile