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Vinicius V. Oliveira, Nassim S. Calixto, Roberto T. Sudo, Adalmir M. Dantas; The Effect Of Local Anesthetics On Retinal Spreading Depression. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2460.
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Although many studies have been made about the pathophysilogy of spreading depression (SD), many questions still remain. The relationship between SD and many central nervous disorders have been described. In this context, we studied the effects of local anesthetics lidocaine, racemic bupivacaine(RB), R(+) bupivacaine, S(-) bupivacaine and S(-) ropivacaine in this phenomenom.
The protocol was approved by the Institutional Animal Care and Research of Federal University of Rio de Janeiro. The experiments were performed on strips of retina from White Leghorn chicks. Those strips were superfused with a modified Ringer solution (Rs) for 15 minutes and a mechanical stimulus was made by a sharpened needle of tungsten, as the control procedure. After that, local anesthetics were added to the Rs in crescent molarities with a 15 minutes superfusion time for each concentration. In the end of the experiment, the retina was superfused by Rs again. The extracellular slow voltage shift (SVS) was measured by a Grass polygraph with 2 electrodes positioned in the inner plexiform layer.
Results are shown on the tables as Mean±StdError. Table 1 shows the rate between the slow voltage shift (SVS) obtained after the anesthetic was administered and the control SVS. Table 2 shows the rate between the time necessary to the wave pass through the 2 electrodes after the anesthetic superfusion and the control procedure. Significant difference against the control p<0.001 is shown in italic underlined.
In our study we found S(-) bupivacaine > RB > R(+) bupivacaine > S(-) Ropivacaine > Lidocaine at decreasing effectiveness order on the blockage of SD. Over more, a dose-response effect was observed in all anesthetics diminishing the SVS and slowing the propagation velocity of the SD, and at the end, the last wave is very similar to the control wave. It is interesting because it follows the pattern of action on nervous effect of local anesthetics. Otherwise, the lack of effect of TTX over SD (Martins-Ferreira 1981), lead us to think that the retina presents a specific Na-channel TTX resistant.
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