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, 25 (4), 238-44

Antinociceptive Effects of Intraperitoneal and Intrathecal Vitamin E in the Rat Formalin Test

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Antinociceptive Effects of Intraperitoneal and Intrathecal Vitamin E in the Rat Formalin Test

Myoung Joong Kim et al. Korean J Pain.

Abstract

Background: Vitamin E is widely known to be one of the reactive oxygen species (ROS) scavengers and a drug that can easily be obtained, and it has been shown to attenuate the pain responses induced by various causes in animal pain models. Thus, this experiment was conducted to assess the antinociceptive effects of vitamin E by comparing intraperitoneal and intrathecal injections in rats subjected to the formalin test.

Methods: AFTER THE INTRAPERITONEAL AND INTRATHECAL INJECTIONS OF VITAMIN E WERE CARRIED OUT, RESPECTIVELY (IP: 500 mg/kg, 1 g/kg, and 2 g/kg, IT: 3 mg/kg, 10 mg/kg, and 30 mg/kg), the formalin test was perfumed. As soon as 5% formalin was injected into left hind paw, the number of flinches induced by pain was measured at 5-minute intervals for 1 hour.

Results: Formalin injected into the left hind paw induced biphasic nociceptive behavior in all animals. Intraperitoneal injection of vitamin E diminished the nociceptive behavior in a dose-dependent manner during the early and late phase. Intrathecal vitamin E diminished nociceptive behavior dose dependently during the late phase but showed no significant difference in the early phase.

Conclusions: Vitamin E attenuated acute nociception when it was injected systemically, while both systemic and intrathecal injection produced analgesia in a rat model of formalin-induced hyperalgesia.

Keywords: formalin test; intraperitoneal; intrathecal; vitamin E.

Figures

Fig. 1
Fig. 1
Time effect curve of intraperitoneal injection group. Vitamin E was administered 1 hour before formalin injection. Each point showed the mean ± SE and significant dose-dependent decreases in flinches in the early phase (0-5 min) and late phase (10-60 min). *P < 0.05, vitamin E 500 mg/kg compared with the control group. P < 0.05, vitamin E 1 g/kg compared with the control group. P < 0.05, vitamin E 2 g/kg compared with the control group.
Fig. 2
Fig. 2
Time effect curve of intrathecal injection group. Vitamin E was administered 20 minutes before formalin injection. Each point showed the mean ± SE and significant dose-dependent decreases in flinches in the late phase (10-60 min). *P < 0.05, vitamin E 3 mg/kg compared with the control group. P < 0.05, vitamin E 10 mg/kg compared with the control group. P < 0.05, vitamin E 30 mg/kg compared with the control group.
Fig. 3
Fig. 3
Dose-response curve of the early phase in intrathecal and intraperitoneal injection group respective. Each point showed the mean ± SE and non-significant difference between control and intrathecal injection group but significant dose-dependent decreases of flinches in intraperitoneal injection group. IT: intrathecal injection, IP: intraperitoneal injection. *P < 0.05, intraperitoneal injection compared with the control group.
Fig. 4
Fig. 4
Dose-response curve of the late phase in intrathecal and intraperitoneal injection group respective. Each point showed the mean ± SE and significant dose-dependent decreases of flinches in both injection group. IT: intrathecal injection, IP: intraperitoneal injection. *P < 0.05, intrathecal injection compared with the control group. P < 0.05, intraperitoneal injection compared with the control group.

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