Ratlarda nöroenflamasyonun nöropatik ağrıya etkisi

The aim of this experimental study is to investigate whether there is any association between the chronic neuroinflammation induced by Lipopolysaccharide (LPS) on neuropathic pain (NP) produced by applying the infraorbital nerve chronic constriction injury (IoN-CCI) and the alterations on microglia and astrocytes in CNS in rats. 24 male, 14-16 weeks adult, Sprague-Dawley rats with the weight of 200–250 g were used. Two experimental groups were randomly made according to the perineural injection they received Vehicule (Vhcl-saline) and LPS groups depend on the receiving 50 μL Vhcl or 50 μL of LPS in NaCl 0.5 % for each perineural injection. Each group was included 12 rats. Two different parameters (i) the evaluation of spontaneous pain by quantifying the isolated facial grooming (iFG) episodes and (ii) evaluation of mechanical static allodynia (MSA) by a graded series of Von Frey filament (VFF) testing were performed for behavioral assessments on day -1, 1, 8, 15, 22, 27, 31, 35, 39. CCI-IoN was performed on day 23. The detection of microglia and astrocytes alterations on spinal trigeminal nucleus caudalis (Sp5c) were performed immunohistochemically by using CD68 and GFAP antibodies, respectively. A significant increase was found in iFG responses of Vhcl and LPS groups (p<0.01). iFG (the spontaneous pain) in LPS was achieved on day 8, 22, and the increase rate of iFG in LPS group was more significant (p=0.001). There were significant differences in the mean VFF scores (MSA) of 10 gr between Vhcl and LPS groups on days 1 (p=0.045), while there were significant differences in the mean VFF scores (MSA) of 6 gr between Vhcl and LPS groups on days 8 (p=0.004). Repeated perineural LPS injections produced a significant increase in spontaneous pain as compared to Vhcl on days -1, 8, 22 (P < 0.001). A statistically significant increase was found in VFF scores (MSA) of 2,4,6,8,10 grs in Vhcl and LPS groups by time (p=0.001, p<0.01). Repeated perineural LPS injections produced a significant increase in VFF testing scores between day 1 and day 22 following the first injection, showing increased MSA, as compared to the Vhcl group. There were no statistical significances found in between groups and, the mean CD68 and GFAP-positivity according to both sides of Sp5c (p>0.05). The mean CD68 and GFAP-positivity in both sides in Vhcl and LPS groups were statistically significant (p<0.01). The increased GFAP-positivities both sides were found in each group. A negative correlation was found between CD68-positivities on both sides of Sp5c and VFF 4 gr in the LPS group (r=-0,828 and r=-0,828, p<0,05, respectively) while no correlation was found between iFG and CD68 and GFAP-positivities on both sides of Sp5c in Vhcl group (p>0,05). We concluded that (i) IoN-CCI induced NP connected with central sensitization, showed the reactive astrocytes and reflect mirror image MSA (ii) it supports the hypothesis that microglia can be significant for initiation, while astrocytes are important for the maintenance of NP.