Effects Of NO Synthesis Inhibition On Pain Threshold And On Function Of NMDA Receptor And GABA_A Receptor Of Rats.

Abstract 1Effects of NO synthesis inhibition on pain threshold of ratsObjective:To investigate the effects of NO synthesis inhibition on the pain threshold of rats. Methods: Sprague-Dawley rats were divided into baseline group L-NAME groups and saline groups.L-NAME was administered via intraperitoneal injection at a dose of 50mg/kg .In acute experiment,study was carried 15 min and 30 min after the injection. In chronic experiment, L-NAME was administered twice a day at the same dose and last for 1, 4 and 7 days .Brief pulse of CO2 laser radiation was used to determine laser duration as parameter of pain threshold. Results: The baseline value of pain threshold was 95 ?3.78ms .Pain threshold had no significant changes in saline groups and in acute experiment. In chronic experiment,pain threshold increased in the 1-day group(133.33?7.51ms ) and the 4-days group ( 126.67 +10.33ms ) but had no changes in 7-days group(ll 1.67 +7.53ms). Conclusions: The pain threshold had no changes in acute experiment .In chronic experiment, the pain threshold increased in the 1-day group and the 4-days group but had no changes in the 7-days group .indicating that a mechanism of compensation occurred during the recovery of the painthreshold.