The sensitivity to thermal pain is dose-dependently altered by intra-BLA injection of orexin A

سال انتشار: 1398
نوع سند: مقاله کنفرانسی
زبان: انگلیسی
مشاهده: 414

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شناسه ملی سند علمی:

NSCMED08_161

تاریخ نمایه سازی: 15 دی 1398

چکیده مقاله:

Background and Aim : The amygdala is a complex structure that is essential for processing both fearful and rewarding environmental stimuli. This nucleus is consist of multiple interconnected nuclei including the basolateral complex (BLA), the corticomedial complex and the central nucleus of the amygdala (CeA). The BLA consists of excitatory glutamatergic neurons and inhibitory GABAergic interneurons. Also, it has massive neural connections with lateral hypothalamus (LH). Also, LH is rich in orexinergic neurons which modulate various brain functions such as appetite, sleep-wake cycle and pain. Also, the BLA nucleus plays an important role in anxiety, fear, aversive memory and learning, social behavior, reward behavior and pain modulation. Moreover, neural projections of the descending pain modulatory pathway are originating from the amygdala and terminated in the dorsal horn of spinal cord. Therefore, the purpose of this study was to assess the role of orexin A in the pain modulation by BLA nucleus of the amygdala.Methods : In this study, male Wistar rats weighing 200–270 g (n=7 per group) were purchased from the animal facility of Baqiyatallah University of Medical Sciences. Animals were anaesthetized with 60 mg/kg ketamine and 7.5 mg/kg xylazine and fixed in a stereotaxic apparatus. The stainless steel 23-gauge guide cannulas equipped with a 30-gauge stylet were unilaterally implanted in the right BLA nucleus. After recovery period, orexin A were injected into the BLA nucleus, and 5 Minutes later, the tail flick and hot plate tests were done by 60 seconds intervals. Every test was recorded for 70 minutes with 10 minutes intervals. At the end of the tests, animals were anesthetized and their brains were removed and examined for the correct cannula implantation in the BLA nucleus.Results : Our results demonstrated intra-BLA injection of the lowermost dose (1 μM) of orexin A significantly decreased the latency to response in the hot plate test. The sensitivity to thermal pain was not altered by intra-BLA injection of 50 and 100 μM orexin A. However, intra-BLA injection of the highest dose (150 μM) of orexin A significantly increased the latency to response in the hot plate and tail flick tests.Conclusion : Based on the results of present study, it can be concluded that the orexin A has dose-dependent effect on the sensitivity to thermal pain in the hot plate and tail flick tests. Therefore, the highest dose of orexin A exerts antinociceptive effect in the BLA complex of the amygdala. Conversely, the lowest dose of orexin A has pronociceptive effect in this structure.

نویسندگان

Maryam Eqbali

Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran

Roghaieh Khakpay

Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran

Homeira Hatami-Nemati

Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran

Alireza Ali-Hemmati

Department of Anatomical Science, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran