Postoperative pain and analgesic responses are similar in male and female Sprague-Dawley rats.
OBJECTIVE
Controversy exists concerning the influence of gender on pain sensitivity and response to analgesics both in animal and human studies. The present study compares postoperative pain scores in male and female rats and how they respond to analgesic interventions.


METHODS
Unilateral plantar foot incisions were made in Sprague-Dawley rats of both genders, producing mechanical allodynia in an established model of postoperative pain. Postoperative pain scores were monitored for four days following incision to identify intrinsic differences between the two groups. Animals were tested with analgesics (opioids, alpha(2)-adrenergic agonists, acetylcholine esterase inhibitors, gabapentin) both systemically and intrathecally on the day after incision to assess gender differences in the anti-allodynic effect of these drugs.


RESULTS
In the plantar foot incision model of postoperative pain there was no gender difference in postoperative mechanical hypersensitivity (von Frey filaments) over four days. Morphine (3 mg x kg(-1)) and gabapentin (25 mg x kg(-1)) administered intraperitoneally decreased postoperative mechanical hypersensitivity, but with no gender difference. Intrathecal morphine (1-2 nmol), gabapentin (60-120 nmol), clonidine (45 nmol), and neostigmine (6.6 nmol) also showed no gender difference in analgesic effect.


CONCLUSIONS
The results of this study demonstrate that in Sprague-Dawley rats there are no gender differences in postoperative pain perception or the response to analgesics, indicating that this strain of rats can be used without introducing gender bias in studies of postoperative pain.
Kroin
Jeffrey S
JS
Department of Anesthesiology, Rush Medical College, Chicago, Illinois 60612, USA. jkroin@rush.edu
Buvanendran
Asokumar
A
Nagalla
Subhash K S
SK
Tuman
Kenneth J
KJ
D000085:Acetates / Q000008:administration & dosage / Q000494:pharmacology; D000588:Amines; D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002800:Cholinesterase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology; D003509:Cyclohexanecarboxylic Acids; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005260:Female; D005528:Foot / Q000601:surgery; D000077206:Gabapentin; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D009388:Neostigmine / Q000008:administration & dosage / Q000494:pharmacology; D010147:Pain Measurement / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects* / Q000502:physiology; D010149:Postoperative Pain / Q000188:drug therapy*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D005680:gamma-Aminobutyric Acid
D000085:Acetates; D000588:Amines; D000700:Analgesics; D000701:Analgesics, Opioid; D002800:Cholinesterase Inhibitors; D003509:Cyclohexanecarboxylic Acids; D009388:Neostigmine; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D009020:Morphine; D003000:Clonidine