Effect of intrathecal and intravenous administration of oxytocin on amplitude of the reflex-evoked muscle action potential after electrical stimulation of the tooth pulp in anesthetized dogs.
OBJECTIVE
To determine whether intrathecal (IT) or IV administration of oxytocin will diminish amplitude of the reflex-evoked muscle action potential (REMP) in the digastricus muscle during electrical stimulation of the tooth pulp in anesthetized dogs, thus suggesting an analgesic effect for oxytocin.


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 by both the IT and IV routes of administration. Noninvasive dental dolorimetry was used to assess changes in pain threshold following administration of treatments. Effectiveness of analgesia was determined on the basis of change in REMP amplitude in the digastricus muscle.


RESULTS
Morphine administered IV significantly inhibited REMP amplitude, compared with IV administration of saline solution or oxytocin. There was not a significant change in REMP amplitude between saline solution and oxytocin administered IV. Intrathecal administration of morphine significantly inhibited REMP amplitude, compared with IT administration of saline solution or oxytocin. Intrathecal administration of oxytocin significantly increased REMP amplitude, compared with IT administration of saline solution or morphine.


CONCLUSIONS
Although IV administration of oxytocin did not have an effect on REMP amplitude, compared with IV administration of saline solution, IT administration of oxytocin had the opposite effect of morphine and increased REMP amplitude of the digastricus muscle. These data do not support the use of oxytocin as an analgesic agent in dogs.
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
D000200:Action Potentials / Q000187:drug effects*; D000700:Analgesics / Q000008:administration & dosage* / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D003782:Dental Pulp / Q000187:drug effects* / Q000502:physiology*; D004285:Dogs; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D007275:Injections, Intravenous; D007278:Injections, Spinal; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D010121:Oxytocin / Q000008:administration & dosage* / Q000494:pharmacology* / Q000627:therapeutic use; D010146:Pain / Q000188:drug therapy / Q000517:prevention & control; D010147:Pain Measurement; D013997:Time Factors
D000700:Analgesics; D010121:Oxytocin; D009020:Morphine