Showing 5 results for Sarihi
Talieh Shirafkan, Maryam Sharifi, Alireza Komaki, Abdolrahman Sarihi,
Volume 25, Issue 4 (Fall 2022)
Abstract
Introduction: Diabetic neuropathic pain is a common complication of diabetes. While previous research has shown that direct administration of the neuropeptide orexin-A into the brain can elicit analgesic effects, the specific central nervous system regions and mechanisms mediating these pain-relieving actions remain incompletely characterized.
Methods: The current study used male Wistar rats to investigate the antinociceptive effects of administering orexin-A directly into the ventrolateral periaqueductal gray (vlPAG) region of the midbrain, assessed via the tail-flick test performed 5 minutes post-injection. The experiments compared the effects of intra-vlPAG orexin-A administration in both healthy control and diabetic animal models.
Results: In the control groups, the analgesic effects of intra-vlPAG orexin-A were found to be sustained over the 1-hour observation period. Importantly, orexin-A elicited a rapid and potent analgesic response in the diabetic animal groups as well.
Conclusion: Collectively, these findings suggest a key functional role for the vlPAG orexinergic system in modulating pain tolerance, with implications for the potential therapeutic targeting of this system in the management of debilitating neuropathic pain conditions like diabetic peripheral neuropathy.
Abdolrahman Sarihi, Talieh Shirafkan, Alireza Komaki,
Volume 26, Issue 2 (Spring 2023)
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.
Talieh Shirafkan, Alireza Komaki, Abdolrahman Sarihi,
Volume 26, Issue 3 (Summer 2023)
Abstract
Introduction: To date, a multitude of neural circuits within the central nervous system have been recognized for their roles in pain modulation. Notably, the ventrolateral periaqueductal gray (vlPAG) region of the midbrain emerges as a pivotal element within the supraspinal pain modulation network. This region’s significance has been thoroughly documented across diverse animal pain models. In our study, we concentrated on exploring the functions of capsaicin receptors in this specific area, particularly their involvement in mediating antinociceptive effects.
Methods: In this study, male Wistar rats were utilized to examine the antinociceptive effects of capsaicin when directly administered into the ventrolateral periaqueductal gray (vlPAG) region of the midbrain. The efficacy of this intervention was evaluated using the tail-flick test, conducted five minutes after injection. The research compared the outcomes of intra-vlPAG capsaicin administration between healthy control rats and those with diabetes.
Results: In the control groups, capsaicin induced a swift and temporary analgesic effect, but it did not produce antinociceptive effects in diabetic rats.
Conclusion: Acute microinjections of capsaicin failed to elicit significant antinociceptive effects in the diabetic animal group. To derive more precise conclusions, it is advisable to also examine the long-term impacts of these compounds.
Azam Naderi Farjam, Maryam Sharifi, Alireza Komaki, Abdolrahman Sarihi,
Volume 27, Issue 1 (Winter 2024)
Abstract
Introduction: Diabetic neuropathies (DN) are neuropathic disorders associated with diabetes mellitus. Peripheral neuropathy, characterized by hyperalgesia, can occur in all types of diabetes. Morphine inhibits the activity of locus coeruleus (LC) neurons, which are involved in pain modulation. The capsaicin receptor (TRPV1) is expressed in several brain nuclei involved in pain perception, including the LC nucleus. This study was conducted to examine the role of TRPV1 in the LC on morphine-induced analgesia in morphine-dependent and non-dependent rats affected by DN.
Methods: This study was conducted on male Wistar rats. Diabetic neuropathy (DN) was induced by a single dose of STZ. Morphine sulfate was injected intraperitoneally (3 mg/kg) once daily for 3 days. Finally, we investigated the role of TRPV1 receptors (10 nmol) in the locus coeruleus (LC) in morphine analgesia in both normal and neuropathic rats.
Results: Our results indicated that activating TRPV1 receptors in the locus coeruleus (LC) has no effect on morphine analgesia in normal, non-dependent rats. However, in morphine-dependent animals, it can potentiate morphine analgesia 45 minutes after the injection of a TRPV1 agonist. In diabetic neuropathy (DN) and non-dependent rats, TRPV1 activation increased morphine analgesia 30 minutes after injection but had no effect on dependent rats.
Conclusion: The results of this study suggest that activating the capsaicinoid system could be a useful approach in pharmacological therapy for patients with peripheral neuropathy.
Azam Naderi-Farjam, Maryam Sharifi, Alireza Komaki, Abdolrahman Sarihi,
Volume 27, Issue 4 (Fall 2024)
Abstract
Introduction: Diabetic neuropathies (DN), a group of neuropathic disorders linked to diabetes mellitus, often manifest as peripheral neuropathy characterized by hyperalgesia and can affect all forms of diabetes. Morphine is known to inhibit the activity of locus coeruleus (LC) neurons, which play a crucial role in pain modulation. The TRPV1 receptor, associated with capsaicin, is expressed in several brain nuclei involved in pain perception, including the LC nucleus. This study aims to investigate the influence of TRPV1 in the LC on thermal hyperalgesia in both morphine-dependent and non-dependent rats suffering from DN.
Methods: This study involved male Wistar rats, with diabetic neuropathy (DN) induced by administering streptozotocin (STZ) at a dose of 60 mg/kg. Morphine sulfate, at a dosage of 3 mg/kg, was administered intraperitoneally once daily for three consecutive days. Subsequently, we explored the activation of TRPV1 channels using capsaicin, at a concentration of 10 nmol, in mediating thermal hyperalgesia in both normal and neuropathic rats.
Results: Our findings revealed that activation of TRPV1 receptors in the LC significantly restored the decreased hot plate threshold in diabetic non-dependent rats. Conversely, this activation had no impact on diabetic-morphine-dependent rats.
Conclusion: The findings of this study imply that targeting the capsaicinoid system may serve as an effective pharmacological strategy for treating patients with peripheral neuropathy.
