Preconditioning abolishion by midazolam in isolated hearts of rats.
OBJECTIVE
To study the effects of benzodiazepine midazolam in the coronary flow (Cflo), cardiac frequency (CF) and myocardial contractility in isolated hearts of rats subjected to ischemic preconditioning (IPC).


METHODS
30 Wistar rats were used, undistinguished by gender. After anesthesia with ethyl ether, the hearts were put into perfusion (Krebs-Henseleit solution, 95% O2 and 5% CO2, 37 degrees C, 110-120mmHg), in disposable Langendorff type system. Five groups of six animals were constituted: GI- Control; GII- Ischemia; GIII- IPC; GIV- Ischemia + 100mcg of midazolam; GV- IPC + 100mcg of midazolam. After stabilization (t0), and on times t5, t10, t15, t20 and t25, CF, Cflo, systolic pressure (SP) and diastolic pressure (DP) and dP/dt were recorded. DP was maintained at 5 +/- 2 mmHg. The statistical method ANOVA and Tukey Test were employed for p < or = 0.05.


RESULTS
No significant variations have occurred between Cflo and CF. On Pd/td, differences have occurred (p<0.05) between groups I and II (respectively 94.7+/-23.0 and 62.3+/-12.1%). The preconditioning (GIII), improved significantly the results in the group II (respectively 62.3+/-12.1 and 87.1+/-12.4 %). The decrease in dP/dt in group II was not prevented by midazolam (GIV) (62.3+/-12,1 and 60.5+/-15.8 %). In group III, dP/dt was 87.1+/-12.4%, whereas in group V, only 55.5+/-17.2% (p<0.05)


CONCLUSIONS
Midazolam, when administered before the ischemia, was unable to prevent the ischemic deterioration of the myocardium. When administered before the preconditioning, it has abolished its protective effect.
Gomes
Otoni Moreira
OM
Surgery Department, Minas Gerais Federal University, Belo Horizonte - MG, Brazil. gomes@servcor.com
Valladares
Ubirajara Fernandes
UF
Santos
Carlos Henrique Marques dos
CH
Abrantes
Rafael Diniz
RD
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects*; D004195:Disease Models, Animal; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D008874:Midazolam / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects*; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control; D051381:Rats; D017208:Rats, Wistar
D014151:Anti-Anxiety Agents; D008874:Midazolam