Use of noninvasive dental dolorimetry to evaluate analgesic effects of intravenous and intrathecal administration of morphine in anesthetized dogs.
OBJECTIVE
To determine whether changes in amplitude of the reflex-evoked muscle action potential (REMP) elicited by noninvasive dental dolorimetry (electrical stimulation of the tooth pulp) in anesthetized dogs may be used to objectively evaluate the effectiveness of IV and intrathecal (IT) administration of morphine.


METHODS
6 male Beagles that were 2 to 6 years old.


METHODS
Dogs were used in a crossover design with at least a 5-day washout period between treatments. Each dog received morphine, saline (0.9% NaCl) solution, and oxytocin via the IV and IT routes of administration; however, only results for morphine and saline treatments were reported here. Dogs were anesthetized and prepared for noninvasive dental dolorimetry. After IV or IT administration, electrical stimulation was applied to a tooth, and REMPs of the digastricus muscle were recorded at 5-minute intervals for 60 minutes. To determine differences in REMP amplitude between treatments, a linear regression line was fitted for each dog-treatment combination.


RESULTS
The IV administration of morphine significantly inhibited REMP amplitude, compared with IV administration of saline solution. Intrathecal administration of morphine significantly inhibited REMP amplitude, compared with IT administration of saline solution.


CONCLUSIONS
Noninvasive dental dolorimetry in anesthetized dogs has promise as a technique for use in evaluating the analgesic potential of drugs administered IV and IT through evaluation of their effect on REMP amplitude recorded for the digastricus muscle.
Brown
Dorothy C
DC
Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104-6010, USA.
Bernier
Noemie
N
Shofer
Frances
F
Steinberg
Sheldon A
SA
Perkowski
Sandra Z
SZ
D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000627:therapeutic use; D000758:Anesthesia; D000818:Animals; D003782:Dental Pulp; D004283:Dog Diseases / Q000188:drug therapy* / Q000517:prevention & control; D004285:Dogs; D005071:Evoked Potentials; D007275:Injections, Intravenous; D007278:Injections, Spinal; D008297:Male; D009020:Morphine / Q000008:administration & dosage* / Q000627:therapeutic use*; D010146:Pain / Q000188:drug therapy* / Q000517:prevention & control / Q000662:veterinary*; D010147:Pain Measurement / Q000379:methods*; D013997:Time Factors
D000701:Analgesics, Opioid; D009020:Morphine