Metabólitos de óxido nítrico no interstício da medula espinhal lombossacral e no líquido cefalorraquidiano em ratas com cistite aguda induzida por ciclofosfamida: um estudo in vivo com microdiálise

Abstract

Objective:To determine the concentration of nitrate/nitrite in the cerebrospinal fluid and in the dorsal horn interstice of the L6-S1 spinal cord boundary in rats with or without cystitis induced by cyclophosphamide.Methods:All experiments were conducted using Wistar female rats. A microdialysis probe was implanted in the subarachnoid space or in the spinal cord tissue at the L6-S1 segments (confirmed histologically). Two days later, the microdialysis probe was perfused with artificial cerebrospinal fluid, containing or not NGmonomethyl-L-arginine. Samples were collected every 15 minutes and kept at −20°C. Nitrite/nitrate concentrations were determined by chemiluminescence.Results:In normal animals, the mean values of nitrite/nitrate concentrations in the first microdialysate sample of the cerebrospinal fluid and of the spinal cord interstice were similar (482.5±90.2pmol/75μL, n=20, and 505.7±11.5pmol/75μL, n=6, respectively), whereas, in the samples from rats with cystitis, these values were significantly greater (955.5±66.3pmol/75μL, n=8, and 926.5±131.7pmol/75μL, n=11, respectively). In both groups, NGmonomethyl-L- arginine caused a significant reduction in the nitrite/nitrate concentration. Interestingly, the maximal reduction of nitrite/nitrate concentration caused by NG-monomethyl-L- arginine was no greater than 30% of the initial values.Conclusions:These results constitute the first demonstration that nitrite/nitrate concentrations in the cerebrospinal fluid and spinal cord interstice are elevated between 20- and 22 hours after cyclophosphamide-induced cystitis, and indicate that cystitis is associated with changes in the production of nitric oxide in the spinal cord segments, where most primary bladder afferents end.

Extracellular adenosine 5’-triphosphate concentrations changes in rat spinal cord associated with the activation of urinary bladder afferents. A microdialysis study

“…The procedure to implant the microdialysis probe was conducted as previously described. (17) Briefly, using a dental drill (with a 300μm diameter steel burr), a small hole was made in both lamina of L 2 vertebra. After that, a tubular fiber (200μm diameter) 6.0cm in length, coated with a thin layer epoxy (except for a 2mm middle region that remained uncoated constituting the effective zone for microdialysis) was introduced through these holes, in order to position it in the interstice of L 6 -S 1 spinal cord segment boundary to dialyze the dorsal horn and the dorsal commissure.…”