Korean J Pain.
2018 Jan;31(1):10-15. 10.3344/kjp.2018.31.1.10.
Allopregnanolone suppresses mechanical allodynia and internalization of neurokinin-1 receptors at the spinal dorsal horn in a rat postoperative pain model
- Affiliations
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- 1Department of Anesthesiology, Tsukuba University Hospital, Tsukubba, Japan.
- 2Department of Anesthesiology, Tsuchiura Center for Medical Education and Training, Faculty of Medicine, University of Tsukuba (National Hospital Organization, Kasumigaura Medical Center), Tsuchiura, Japan. taekof@md.tsukuba.ac.jp
- 3Social Welfare Organization, Mito-Saiseikai Hospital, Mito, Japan.
- 4Department of Anesthesiology, School of Medicine, Dokkyo Medical University, Mibu, Japan.
- 5Department of Anesthesiology, University of Tsukuba, Faculty of Medicine, Tsukuba, Japan.
- KMID: 2400903
- DOI: http://doi.org/10.3344/kjp.2018.31.1.10
Abstract
- BACKGROUND
To identify a new strategy for postoperative pain management, we investigated the analgesic effects of allopregnanolone (Allo) in an incisional pain model, and also assessed its effects on the activities of the primary afferent fibers at the dorsal horn.
METHODS
In experiment 1, 45 rats were assigned to Control, Allo small-dose (0.16 mg/kg), and Allo large-dose (1.6 mg/kg) groups (n = 15 in each). The weight bearing and mechanical withdrawal thresholds of the hind limb were measured before and at 2, 24, 48, and 168 h after Brennan's surgery. In experiment 2, 16 rats were assigned to Control and Allo (0.16 mg/kg) groups (n = 8 in each). The degree of spontaneous pain was measured using the grimace scale after the surgery. Activities of the primary afferent fibers in the spinal cord (L6) were evaluated using immunohistochemical staining.
RESULTS
In experiment 1, the withdrawal threshold of the Allo small-dose group was significantly higher than that of the Control group at 2 h after surgery. Intergroup differences in weight bearing were not significant. In experiment 2, intergroup differences in the grimace scale scores were not significant. Substance P release in the Allo (0.16 mg/kg) group was significantly lower than that in the Control group.
CONCLUSIONS
Systemic administration of Allo inhibited mechanical allodynia and activities of the primary afferent fibers at the dorsal horn in a rat postoperative pain model. Allo was proposed as a candidate for postoperative pain management.
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