Effects of l-tetrahydropalmatine on locomotor sensitization to oxycodone in mice.
OBJECTIVE
Recent studies have shown that l-tetrahydropalmatine (l-THP), an active component of Corydolis yanhusuo, can inhibit the development of the conditional place preference induced by opioid receptor agonists, but the effects of l-THP on locomotor sensitivity induced by opioid receptor agonists have not been documented. In the present study, the effects of l-THP on locomotor sensitization to oxycodone, which is an opioid receptor agonist, were studied.


METHODS
Mice treated daily for 7 d with 5 mg/kg oxycodone and challenged with the same dose after 5 days of washout showed locomotor sensitization. In order to study the effects of l-THP on locomotor sensitization induced by oxycodone, l-THP was administered at doses of 6.25, 12.5, and 18.75 mg/kg, 40 min prior to treatment of oxycodone.


RESULTS
l-THP per se did not affect the locomotor activity at the doses of 6.25, 12.5, and 18.75 mg/kg, but could antagonize the hyperactivity induced by oxycodone (5 mg/kg). Co-administration of l-THP (18.75 mg/kg), 40 min prior to oxycodone, could inhibit the development of sensitization to oxycodone. In addition, l-THP (6.25, 12.5, and 18.75 mg/kg, i.g.) dose-dependently prevented the expression of oxycodone sensitization.


CONCLUSIONS
These results suggested that l-THP could attenuate the locomotor-stimulating effects of oxycodone and inhibit the development and expression of oxycodone behavioral sensitization.
Liu
Yan-li
YL
Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China.
Liang
Jian-hui
JH
Yan
Ling-di
LD
Su
Rui-bin
RB
Wu
Chun-fu
CF
Gong
Ze-hui
ZH
D000818:Animals; D001600:Berberine Alkaloids / Q000008:administration & dosage / Q000494:pharmacology*; D031311:Corydalis / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D010098:Oxycodone / Q000037:antagonists & inhibitors*; D010946:Plants, Medicinal / Q000737:chemistry; D011957:Receptors, Opioid / Q000819:agonists
D001600:Berberine Alkaloids; D011957:Receptors, Opioid; C014215:tetrahydropalmatine; D010098:Oxycodone