Effects of intrathecal 6-hydroxydopamine, alpha1 and alpha2 adrenergic receptor antagonists on antinociception of propofol in mice.
OBJECTIVE
To investigate the relationship between spinal cord norepinephrine, alpha1 and alpha2 adrenergic receptors and antinociception of propofol in mice.


METHODS
Kunming mice were used. Antinociceptive tests were investigated with the tail-immersion test and the acetic acid-induced writhing test. The effects of subcutaneous (sc), intrathecal (ith) and intracerebroventricular (icv) injection propofol on pain threshold were observed. The influences of pretreatment with ith 6-hydroxydopamine, alpha1R antagonist prazosin, or alpha2R antagonist yohimbine on the antinociception of propofol were studied.


RESULTS
Significant antinociception was produced by propofol (25, 50 mg/kg, sc) and propofol (20, 40 microg, ith) in tail-immersion test and acetic the acid-induced writhing test (P<0.05 or P<0.01). Icv propofol (10, 20, and 40 microg) did not produce any effect on pain threshold in mice (P>0.05). The 6-hydroxydopamine (5 and 10 microg), prazosin (5 and 10 microg), or yohimbine (5 and 10 microg) ith alone did not affect basal tail-flick latency (TFL) in conscious mice, but significantly reduced the TFL as measured by tail-immersion test in propofol (50 mg/kg, sc)-treated mice, compared with basal TFL and vehicle groups (P<0.05 or P<0.01).


CONCLUSIONS
The spinal cord is a target of propofol antinociception. In mice propofol antinociception is partly mediated by spinal norepinephrine, alpha1R and alpha2R.
Ge
Zhi-Jun
ZJ
Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou 221002, China.
Zeng
Yin-Ming
YM
Tan
Yong-Fei
YF
D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D005260:Female; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D007279:Injections, Subcutaneous; D008297:Male; D051379:Mice; D009619:Nociceptors / Q000187:drug effects; D016627:Oxidopamine / Q000494:pharmacology*; D017288:Pain Threshold / Q000187:drug effects*; D011224:Prazosin / Q000494:pharmacology*; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology*; D013116:Spinal Cord / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology*
D058668:Adrenergic alpha-1 Receptor Antagonists; D058669:Adrenergic alpha-2 Receptor Antagonists; D000700:Analgesics; D015016:Yohimbine; D016627:Oxidopamine; D011224:Prazosin; D015742:Propofol