Scorpion venom component: AGAP exhibits local anaesthetic effects and attenuates nociceptive pain

The incidences of systemic toxicity and other complications associated with existing local anaesthetics can occur at clinical concentration level and vary with the anaesthetic techniques, types of surgery and patient factors. This evidence suggests the need for therapeutic interventions in peripheral and regional anaesthesia. Buthus martensii Karsch (BmK) scorpion venom is a compound that contains mixtures of peptides that have analgesic properties. This study aimed to investigate the local anaesthetic activity of scorpion venom peptide, AGAP (analgesic-antitumor peptide) in mechanical hyperalgesia or acute inflammatory pain. Method: Formalin was injected into the left hind paw after 20 minutes of infiltration of drugs. The time of licking or flinching of the injected hind paw was recorded as indicative of nociceptive or acute inflammatory pain. Paw flinching or quick withdrawal was considered a positive response to pain in the partial sciatic nerve ligation. The paw-withdrawal threshold (PWT) was determined by consecutively increasing and decreasing the magnitude of the stimulus. Results: The results indicated that AGAP exhibited a 67.9% inhibition in licking or flinching time and an 88.1% inhibition in paw withdrawal in mechanical hyperalgesia. The addition of AGAP to lidocaine showed an 89.5% inhibition in paw withdrawal. Conclusion: The data presented in this study suggest that local infiltration of AGAP significantly reduced mechanical hyperalgesia and acute inflammatory pain

Dexmedetomidine alleviates formaldehyde induced pain by inhibiting astrocytes activation in spinal cord / 解剖学报

Objective To investigate the effect of dexmedetomidine ( DEX ) on formaldehyde-induced acute inflammatory pain. Methods Thirty female ICR mice were randomly divided into three groups, including normal saline control (NS) group, formaldehyde(F)group and dexmedetomidine + formaldehyde (DEX+F) group. 0. 1% formaldehyde solution was injected into subcutaneous tissue of mice right hind paw to establish acute inflammatory pain model. An hour before formalin injection, mice were intraperitoneal injected with DEX in DEX + F group, and mice were intraperitoneal injected with equal volume saline in NS group and F group. The expression of spinal cord glial fibrillary acidic protein ( GFAP), which is a astrocytes marker, was detected by immunohistochemistry and Western blotting. Results Spontaneous pain score showed that compared with the NS group, the F group had typical biphasic pain response ; while compared with the F group, the DEX+F group showed a significant decrease in the first (P<0. 001) and second phase pain (P<0. 001). Immunohistochemical result showed that compared with the NS group, the F group had an increase number of GFAP positive cells in the posterior horn of the spinal cord (P<0. 001). However, the DEX+F group showed a decrease number of GFAP positive cells in the posterior horn of spinal cord compared with the F group (P<0. 001 ). Western blotting result showed that compared with the NS group, the F group had increased expression of GFAP in the spinal cord (P<0. 05). Compared with the F group, the DEX + F group showed decreased GFAP expression in the spinal cord ( P < 0. 05 ). Conclusion DEX may improve formaldehyde-induced acute inflammatory pain in mice by inhibiting the activation of astrocytes in the spinal cord.

Correlation between mechanical pain threshold and local blood perfusion in male rat models of acute inflammation induced by carrageenan / 中国比较医学杂志

Objective To explore the relationship between mechanical withdrawal threshold ( MWTs) and local cutaneous blood perfusion ( BP ) in rats with acute inflammation induced by carrageenan.Methods Twenty male Sprague-Dawley ( SD) rats were randomly divided into control and model groups.The acute inflammatory rat model was established by subcutaneously injecting with carrageenan into the left hindpaw.MWTs were measured by Dynamic Plantar Aesthesiometer 37450 before injection ( as base) of carrageenan and at 4 h, 24 h, 48 h, 72 h after carrageenan injection. The local cutaneous BP was detected by Pericam Perfusion Speckle Imager ( Pericam PSI) at the time after measuring of MWTs.The above two behaviors were compared and the relationship between them was analyzed.Results MWTs of the model group rats were decreased while BP significantly increased than that in the control group ( P<0.01 ) .The MWTs and BP in the model rats showed a negative correlation, especially the correlation index showed significant differences at 4 h and 72 h after carrageenan injection ( P<0.01) .Conclusions Carrageenan-induced acute inflammation in rats causes significant changes in mechanical pain threshold, which has a negative correlation with local cutaneous blood perfusion.