Effect of yohimbine on nociceptive threshold in normoglycemic and streptozotocin-treated hyperglycemic mice.
The effects of yohimbine (0.1, 1, 3 and 10 mg/kg SC) on nociceptive threshold were tested in mice using the tail-immersion and hot-plate tests. The tail-flick (withdrawal) latency, a monosynaptic spinal nociceptive response, was significantly lowered by yohimbine. This hyperalgesic response was at its peak 0.5 hr after yohimbine injection. The tail-flick latencies expressed as % of basal latencies were, 95 +/- 8, 100 +/- 10, 62 +/- 10, 33 +/- 7 and 28 +/- 4 in vehicle and 0.1, 1, 3 and 10 mg/kg in yohimbine-treated groups respectively. Yohimbine-induced hyperalgesia was observed when stimulus temperature was either 50 degrees C or 45 degrees C; however, the opiate antagonist naloxone (3 mg/kg SC) induced a hyperalgesic response at 50 degrees C and an analgesic response at 45 degrees C stimulus temperature. Streptozotocin-induced hyperglycemia did not influence the hyperalgesic response of yohimbine. In the hot-plate (60 degrees C) test, which involves higher centers and a polysynaptic nociceptive reflex, yohimbine did not modify the jump latency. The data provide evidence for the presence of a tonic spinal noradrenergic inhibitory control of nociceptive mechanism(s) which does not appear to be readily altered by hyperglycemia.
Bansinath
M
M
Department of Anesthesiology, School of Medicine, New York University Medical Center, NY 10016.
Ramabadran
K
K
Turndorf
H
H
Puig
M M
MM
D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D011930:Reaction Time / Q000187:drug effects*; D012684:Sensory Thresholds; D013696:Temperature; D015016:Yohimbine / Q000494:pharmacology*
D015016:Yohimbine; D009270:Naloxone