Fig. 1:
Enhanced visceromotor response to colorectal distention was observed in response to adult colon inflammation in adult rats subjected previously to neonatal colon inflammation. A. Graph showing the responses of control, neonatal colon inflammation, adult colon inflammation and neonatal/adult inflammation rats to graded colorectal distention, 7 days after initiation of adult colitis, n=6. We found significant effects of both neonatal colon inflammation (F1,27=6.84, p=0.017) and adult colon inflammation (F1,27=19.4, p<0.001) on visceral sensitivity. The visceromotor response to colorectal distention was significantly greater in neonatal/adult inflammation rats vs. adult colon inflammation (*p=0.013), neonatal colon inflammation alone (*p=0.001) and control (*p<0.001) rats. The visceromotor response to colorectal distention in adult colon inflammation rats was significantly greater in adult colon inflammation rats vs. the control (#p=0.03) rats. There was no significant difference in the visceromotor response to colorectal distention between neonatal colon inflammation and control rats. B. Western blot panels and bar graphs showing that BDNF protein expression in lumbar-sacral spinal cord segments was significantly higher in neonatal/adult inflammation rats vs. adult colon inflammation (*p<0.001), control (*p<0.001) and neonatal colon inflammation (*p<0.001) rats. Spinal cord BDNF was also significantly greater in adult colon inflammation rats vs. control rats (#p<0.001, n=6). C. Graph showing BDNF mRNA expression in lumbar/sacral spinal cord segments normalized to 18S rRNA and expressed as fold change with respect to control BDNF mRNA was significantly upregulated in neonatal/adult inflammation vs. adult colon inflammation *p=0.003), control (*p<0.001) and neonatal colon inflammation (*p<0.001) rats, and it was significantly upregulated in adult colon inflammation vs. control (#p=0.013) rats; significant effect of adult colon inflammation: F1,27=32.1, p<0.001 and of neonatal colon inflammation: F1,27=7.63, p=0.012. n=6). D. Bar graph showing BDNF mRNA expression in colon projecting neurons from the S1 dorsal root ganglia that were isolated by laser capture microdissection. We detected a significant neonatal/adult inflammation interaction: F1,23= 9.15, p=0.008, n=5. BDNF mRNA was significantly upregulated in neonatal/adult inflammation vs. adult colon inflammation (*p<0.001), control (*p<0.001) and neonatal colon inflammation rats (*p<0.001), and it was significantly upregulated in adult colon inflammation vs. control (#p=0.035) and neonatal colon inflammation (#p=0.03) rats. There were no significant differences between control and neonatal colon inflammation (p=0.49). Separate groups of animals contributed to visceromotor response data and to tissue for molecular analyses.