Khaleghzadeh-Ahangar H, Sadeghimahalli F, Khandan S, Shahabi S, Moghadamnia A. Insulin within the Arcuate Nucleus Has Paradoxical Effects on Nociception in Healthy and Diabetic Rats. BCN 2020; 11 (6) :727-736
URL:
http://bcn.iums.ac.ir/article-1-1583-en.html
1- Department of Physiology, School of Medicine, Babol University of Medical Sciences, Babol, Iran
2- Departement of Physiology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
3- Neuroscience Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran.
Abstract:
Introduction: Broad neural circuits originate from the hypothalamic arcuate nucleus and project to many parts of the brain which are related to pain perception. Insulin receptors are found in the arcuate nucleus. Since nociception may be affected in type 1 diabetes, the present study aimed to investigate the intra-arcuate nucleus insulin role in pain perception in streptozotocin (STZ)-induced diabetic and healthy rats.
Methods: Regular insulin was microinjected within the arcuate nucleus and the pain tolerance was measured using the hot plate and the tail-flick apparatus in diabetic rats.
Results: The results showed that the arcuate nucleus suppression with lidocaine could increase thermal nociception in non-diabetic animals. Also, insulin within the arcuate nucleus decreased the acute thermal pain perception in these animals. STZ-induced diabetes produced hypoalgesia which the latency of these tests, progressively increased over time after induction of diabetes. Also, in the same animal group, intra-arcuate injection of insulin reduced the latency of nociception.
Conclusion: Intra-arcuate insulin has paradoxical and controversial effects in healthy and diabetic rats’ nociception. These effects seem to be due to the insulin effect on releasing pro-opiomelanocortin and its deriv
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● The arcuate nucleus inhibition increased thermal nociception.
● Administrating insulin within the arcuate nucleus decreased the acute thermal pain perception.
● Streptomycin-induced diabetes makes thermal hypoalgesia.
● Pain response latency progressively increased over time after induction of diabetes.
● Intra-arcuate injection of insulin reduced the latency of thermal nociception in streptomycin-induced diabetes.
Plain Language Summary
The arcuate nucleus is a part of the ventral hypothalamus. It secrets endogenous opioids and projects to several parts of the brain involved in pain perception. The arcuate nucleus contains insulin receptors, and it seems that insulin can excite its neuron to secret the endogenous opioids. In type 1 diabetes, insulin secretion decreases. Accordingly, it appears that the arcuate nucleus excitation decreases because of insulin reduction. The present study illustrated that the arcuate nucleus inhibition by lidocaine increases pain feeling, so this nucleus is a pivotal part of pain sensation. Insulin injection inside the arcuate nucleus reduces pain sensation in healthy rats. Also, type 1 diabetes decreases pain sensation, but insulin injection within the arcuate nucleus increases it. This phenomenon is contrary to the results observed in healthy rats. Therefore, it seems that different mechanisms affect arcuate nucleus neurons in healthy and diabetic rats.
Type of Study:
Original |
Subject:
Behavioral Neuroscience Received: 2019/08/11 | Accepted: 2019/11/8 | Published: 2020/11/1