Research paperAntinociceptive effect of calcitonin gene-related peptide in the central nucleus of amygdala: activating opioid receptors through amygdala–periaqueductal gray pathway
Section snippets
Animal preparation and intra-nucleus injections
Male Sprague–Dawley rats (220–250 g; Institute of Zoology, Chinese Academy of Science, Beijing, China) were used. The rats were housed in cages with free access to food and water, and maintained in a room temperature of 24 °C with a 12-h light/dark cycle. Experiments were conducted according to the guidelines of the animal ethical committee of Karolinska Institutet and every effort was made to minimize both the animal suffering and the number of animals used. The animals were anesthetized by
Effects of intra-CeA administration of CGRP on HWLs in rats
Rats received intra-CeA injection of 0.2 (n=7), 1 (n=8) or 2 nmol of CGRP (n=8), or 1 μl of 0.9% saline (n=8) as a control. Compared with the control group, the HWLs increased significantly after intra-CeA injection of 1 (thermal test: F=33.88, P<0.001; Randall Selitto test: F=3.59, P=0.07) or 2 nmol of CGRP (thermal test: F=11.82, P<0.05; Randall Selitto test: F=10.32, P<0.01), but not 0.2 nmol of CGRP (thermal test: F=1.61, P=0.22; Randall Selitto test: F=1.29, P=0.27), as shown in Fig. 1.
Effects of intra-,CeA injection of CGRP8-37 on the CGRP-induced increase in HWLs of rats
The antinociceptive effect of CGRP in the CeA
It has been reported that i.c.v. injection of CGRP induces antinociception Pecile et al 1987, Candeletti and Ferri 1990. Furthermore, studies in our laboratory found that CGRP elicited antinociceptive effects in the nucleus raphe magnus and the PAG of rats Huang et al 2000, Xu et al 2000. The present study demonstrated that intra-CeA administration of CGRP induced antinociception dose-dependently in rats tested by hotplate test and Randall Selitto test. Furthermore, the antinociceptive effect
Acknowledgements
The study was supported by funds from the National Natural Science Foundation of China (NSFC) and the Karolinska Institute Foundation. We are very grateful to Mr. Ju-Shuai Zhang for generously supplying us with Fast Blue and to Miss Qingqing Han and Mr. Yun Zhao for the assistance in processing the microphotographs.
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2021, Progress in NeurobiologyCitation Excerpt :Electrophysiology experiments in rodents suggest that CGRP drives potentiation in the right CeA by increasing the amplitude of NMDA-mediated EPSCs (Han et al., 2010; Okutsu et al., 2017), most likely through CGRP receptor-driven activation of protein kinase A (PKA) (Han et al., 2005). In another study, pharmacological infusion of CGRP into the left CeA of naïve rats increases mechanical hindlimb threshold (side not specified), suggesting an anti-nociceptive effect (Xu et al., 2003). It is possible that CGRP has different roles in the left and right CeA, or its role could depend on pain modality or chronicity.