Acta Pharmacologica Sinica 2005 February; 26 (2): 186-191; doi: 10.1111/j.1745-7254.2005.00033.x

Aim: To investigate the relationship between spinal cord norepinephrine, α₁ and α₂adrenergic 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, α₁R antagonist prazosin, or α₂R 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 µg, 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 µg) did not produce any effect on pain threshold in mice (P>0.05). The 6-hydroxydopamine (5 and 10 µg), prazosin (5 and 10 µg), or yohimbine (5 and 10 µg) ith alone did not affect basal tai-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).

Conclusion: The spinal cord is a target of propofol antinociception. In mice propofol antinociception is partly mediated by spinal norepinephrine, α₁R and α₂R.

Keywords: propofol; spinal cord; antinociception; prazosin; yohimbine; norepinephrine