Aim: 

In this study, Hypericum perforatum L. (HP) aqueous extract was administered intraperitoneally (i.p.) for evaluation of its antinociceptive effect.

Methods: 

For assessment of its site of action, HP was filtered and administered both intrathecally (i.t.) and intracerebroventricularly (i.c.v.). Antinociceptive effects of HP extract were evaluated using formalin and tail-flick pain models.

Results: 

Peripheral effects of HP extract were assessed in three doses (200, 400 and 800 mg kg-I, i.p.) and compared with the antinociceptive effect of Sodium Salicylate (SS) as a positive control. Administration of 300 mg/kg of SS i.p. had no effect on tail-flick latency, while all doses of extract increased it. In both phases of formalin test, all doses of extract alleviated the animal's nociception, but SS (300 mg kg-I) produced antinociception only in the second phase of formalin test. In central administration, the HP (1 and 2 mg/rat, i.t.) induced analgesia in the tail-flick and both phases of formalin tests. The i. c. v. administration of HP (2 mg/rat) produced analgesia in both phases of formalin test, but not on tail flick latency.

Conclusions: 

The results showed that peripheral and central administration of HP has antinociceptive effect and its spinal effect seems to be more potent than its cerebral effect.