Adverse Effects of Repeated, Intravenous Morphine on Recovery after Spinal Cord Injury in Young, Male Rats Are Blocked by a Kappa Opioid Receptor Antagonist

Journal of Neurotrauma, 2022 · DOI: 10.1089/neu.2022.0208 · Published: December 1, 2022

Spinal Cord Injury Neurology Pain Management

Simple Explanation

Spinal cord injury (SCI) patients often experience pain which is commonly treated with morphine. However, morphine can undermine long-term locomotor recovery. This study tested whether blocking kappa opioid receptors (KORs) with norbinaltorphimine (norBNI) could prevent the negative effects of repeated, intravenous morphine administration after SCI. The study found that blocking KOR activation in young, male rats prevented the negative effects of morphine on locomotor recovery and lesion size, suggesting a potential clinical strategy for pain management without compromising recovery.

Study Duration

42 Days

Participants

38 male Sprague–Dawley rats

Evidence Level

Not specified

Key Findings

1
Blocking KOR activation with norBNI prevented the negative effects of repeated intravenous morphine on locomotor recovery in rats with SCI.
2
Morphine administration increased weight loss following injury, but norBNI appeared to reduce this weight loss.
3
NorBNI treatment reduced morphine-induced tissue loss at the lesion site.

Research Summary

This study investigated the effects of repeated intravenous morphine administration on recovery after spinal cord injury (SCI) in rats, and whether blocking kappa opioid receptors (KORs) with norbinaltorphimine (norBNI) could prevent the negative effects of morphine. The findings showed that blocking KOR activation with norBNI protected against the negative effects of morphine on locomotor recovery and reduced tissue loss at the lesion site. The results suggest that using a KOR antagonist alongside morphine may provide effective pain relief without compromising locomotor recovery after SCI.

Practical Implications

Clinical Pain Management

Using KOR antagonists in conjunction with morphine may allow for effective pain management without compromising locomotor recovery after SCI.

Opioid Selection

Opioids that do not engage the KOR system, such as buprenorphine, might be a better pain management option in the acute phase of SCI.

Further Research

Further investigation into the dose-response effects of morphine on recovery is necessary to optimize treatment strategies.

Study Limitations

1
The study only examined male rats, and the effects of sex were not investigated.
2
Systemic administration of norBNI was not investigated; repeated epidural administrations may not be feasible in clinical pain management.
3
The escalation of the dose of morphine used in present study may be a limitation, as increased cell death might mask effects of morphine on the development of pain.

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