[Evaluation of analgesic effects of morphine, buprenorphine and pentazocine in rats receiving somatic and visceral stimulation].
The analgesic effects of morphine, buprenorphine and pentazocine examined by behavioral responses to tail-flick (TF) and colorectal distension (CD) were studied in rats. Animals were randomly divided into three groups; morphine (M) groups of 4 mg.kg-1 (n = 7), buprenorphine (B) groups of 0.03 mg.kg-1 (n = 8), pentazocine (P) groups of 3 mg.kg-1 (n = 8). After determinations of TF and CD values, animals were administered each analgesic intraperitoneally, and both procedures were repeated every 5 minutes until 40 minutes. Three drugs produced an almost same degree of increase in pain threshold for TF; % maximum possible effects (%MPEs) were approximately 30%. Similar patterns of increase in pain thresholds for CD were observed in M and B groups; %MPEs were approximately 20%. In contrast, P groups showed a significant increase in thresholds for CD compared to M and B groups; 20 minutes after intraperitoneal administration of P, %MPE was approximately 50%. These results indicate that there are different antinociceptive effects to somatic and visceral stimuli between M, B and P, and suggest that selective opioid agonists modulate responses to different kinds of noxious stimuli.
Iwasaki
H
H
Department of Anesthesiology, Sapporo Medical University, School of Medicine.
Ohmori
H
H
Kobayashi
I
I
Omote
K
K
Kawamata
M
M
Namiki
A
A
D015746:Abdominal Pain / Q000188:drug therapy; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D002047:Buprenorphine / Q000494:pharmacology*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects*; D010423:Pentazocine / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
D000700:Analgesics; D002047:Buprenorphine; D009020:Morphine; D010423:Pentazocine