Early preconditioning of the spinal cord was investigated in rabbits, as an eventual protection mechanism, immediately before a 30 min ischemic period. Eight-seven New Zealand rabbits divided into 6 groups were assigned to the study. Ischemia of the spinal cord was induced by crossclamping (C) the abdominal aorta distal to the emergence of the left renal artery. Preconditioning was stimulated by short and sometimes repetitive ischemic periods, underlined in the text, and followed by different periods of reperfusion. Group I - Control: In 20 animals the aorta was crossclamped for 30 min. In two of them (10%) motricity and sensitivity of the hind-legs and tail were entirely restored; the other 18(90%) became paraplegic. Group II - Sham operation: 10 animals were operated as the ones in the previous group except for the fact that the aorta was not clamped. All of them (100%) had their sensitive and motor functions entirely restored. Group III - Preconditioning: 10 animals - (C) 1 min <FONT FACE="Symbol">®</font> 15 min<FONT FACE="Symbol">®</font> (C) 30 min <FONT FACE="Symbol">®</font> final reperfusion. All animals became paraplegic. Group IV - Preconditioning: 6 animals - (C) 1 min <FONT FACE="Symbol">®</font> 5 min<FONT FACE="Symbol">®</font> (C) 2 min <FONT FACE="Symbol">®</font> 5 min <FONT FACE="Symbol">®</font> (C) 2 min <FONT FACE="Symbol">®</font> 5 min <FONT FACE="Symbol">®</font> (C) 30 min final reperfusion. Five rabgbits (83,33%) became paraplegic and 1 (16,66%) became monoplegic. Group V - Chlorpromazine: 20 animals were given chlorpromazine, intravenously, 2 mg/kg, 10 min before aortic crossclamping. Eleven animals (55%) had their sensitive and motor functions reestablished and 9 (45%) became paraplegic. Group VI - Clorpromazine + preconditioning: 21 animals were given chlorpromazine as those of group V and were preconditioned as follows: (C) 1 min <FONT FACE="Symbol">®</font> 5 min <FONT FACE="Symbol">®</font> (C) 1 min <FONT FACE="Symbol">®</font> 5 min <FONT FACE="Symbol">®</font> (C) 30 min <FONT FACE="Symbol">®</font> final reperfusion. Nine animals (32.8%) recovered the sensitive and motor functions and 2(9.52%) experienced partial recovery. The remaining ones (47.68%) became paraplegic. Statistical analysis of the results demonstrated that: 1) there was no significant difference between groups III and IV, and when both of them were compared to group I (p < 0.05); 2) there was no significant difference between groups V and VI, but the difference was significant when both of them were compared to group I (p<0.05). Hystologic study - Twelve animals were assigned exclusively to histologic study: 6 control animals and 6 that were preconditioned as follows: (C) 1 min <FONT FACE="Symbol">®</font> 5 min <FONT FACE="Symbol">®</font> (C) 1 min <FONT FACE="Symbol">®</font> 5 min <FONT FACE="Symbol">®</font> (C) 30 min <FONT FACE="Symbol">®</font> 5 h reperfusion. The percentage of ischemic neuronal cells showed a great dispersion of values, with no significant difference between groups, considering the median of those values (p < 0.005).
Isquemic preconditioning; Spinal chord; Spinal chord protection
