Activation of Orexin-A and Capsaicin Receptors in the Periaqueductal Gray is Ineffective in Reducing Mechanical Allodynia and Thermal Hyperalgesia in Rats | ||
| Pathobiology Reserach | ||
| Article 5, Volume 26, Issue 2, 2023, Pages 49-54 PDF (733.15 K) | ||
| Document Type: Original Research | ||
| Authors | ||
| Abdolrahman Sarihi* 1; Talieh Shirafkan2; Alireza Komaki3 | ||
| 1Department of Neuroscience, School of Sciences and Advanced Technology in Medicine, Hamadan University of Medical Sciences, Hamadan, Iran, Postal code: 6517838736 | ||
| 2Department of Biology, Faculty of Basic Sciences, Islamic Azad University of Hamadan, Iran | ||
| 3Neurophysiology Research Center, Hamadan University of Medical Sciences, Hamadan, Iran | ||
| Abstract | ||
| Introduction: Up to now, numerous neural circuits within the central nervous system have been identified as participants in the modulation of pain. Among these, the ventrolateral periaqueductal gray (vlPAG) region of the midbrain stands out as a crucial component of the pain modulation network at supraspinal levels. Its involvement has been extensively characterized across various animal pain models. In this research, we focused on investigating the roles of orexin A and capsaicin receptors within this region in mediating antinociceptive responses. Methods: In this study, male Wistar rats were utilized to explore the antinociceptive effects of administering orexin-A and capsaicin directly into the ventrolateral periaqueductal gray (vlPAG) region of the midbrain. The substances were administered both separately and in combination. Then, their antinociceptive effects were assessed using the von Frey and hot plate tests post-injection. The experiments compared the outcomes of intra-vlPAG drug administration in both healthy control and diabetic animal models. Results: Microinjections of orexin-A and capsaicin, whether administered individually or in combination directly into the PAG, failed to produce anti-nociceptive effects on mechanical allodynia or thermal hyperalgesia in both healthy and diabetic rats. Conclusion: Acute microinjections of orexin-A and capsaicin did not produce significant anti-nociceptive effects in either healthy or kindled animal groups. To draw more accurate conclusions, it is recommended to investigate the long-term effects of these compounds as well. | ||
| Keywords | ||
| Pain; Mechanical allodynia; thermal hyperalgesia; Orexin A receptor; Capsaicin receptor; Ventrolateral periaqueductal gray; Diabetic neuropathy | ||
| References | ||
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