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Response After Repeated Ketamine Injections in a Rat Model of Neuropathic Pain
1Department of Anesthesiology and Pain Medicine, Inha University Hospital, Inha University School of Medicine, Incheon, South Korea. jhs@inha.ac.kr.
Physiological Research
|March 11, 2022
Summary
Repeated ketamine injections effectively reduced neuropathic pain in rats for over two weeks. However, the pain-relieving effects of ketamine diminished significantly after a two-week break and subsequent re-administration.
Area of Science:
- Neuroscience
- Pharmacology
- Pain Management
Background:
- Ketamine, an N-methyl-D-aspartate antagonist, is known for its analgesic properties.
- Chronic ketamine use may lead to adverse effects such as tolerance and dependency.
- Neuropathic pain models are crucial for studying pain mechanisms and evaluating analgesics.
Purpose of the Study:
- To investigate the efficacy of repeated ketamine injections in a rat model of neuropathic pain.
- To assess the impact of ketamine discontinuation and readministration on its analgesic effects.
- To evaluate potential tolerance development to ketamine's antinociceptive properties.
Main Methods:
- Neuropathic pain was induced in Wistar rats via partial sciatic nerve ligation (PSNL).
- Rats received daily intraperitoneal ketamine injections (5 mg/kg or 10 mg/kg) for four weeks.
- Mechanical withdrawal thresholds were measured weekly using the Von Frey test, with a two-week discontinuation and one-week readministration period.
Main Results:
- The 10 mg/kg ketamine group (K10) demonstrated a significant increase in mechanical withdrawal threshold compared to baseline and the control group.
- Antinociceptive effects in the K10 group persisted for over two weeks of daily injections.
- Ketamine's analgesic effect significantly decreased seven days after readministration compared to the effects observed after 28 days of continuous treatment.
Conclusions:
- Repeated ketamine administration shows significant antinociceptive effects in a rat model of neuropathic pain.
- A notable decrease in ketamine's efficacy was observed after a period of discontinuation and subsequent readministration, suggesting potential for diminished therapeutic effect.
- Further research is warranted to understand the mechanisms underlying ketamine tolerance and to optimize its clinical use in chronic pain management.
