Effects of NO synthesis inhibition on pain threshold and binding capacity of NMDA receptor of hippocampus in rats
- VernacularTitle:一氧化氮合成阻滞对大鼠痛阈和脑海马NMDA受体活性的影响
- Author:
Yongwei WANG
;
Weidong MI
;
Pingping ZUO
- Publication Type:Journal Article
- Keywords:
Receptor, N-methyl-D-aspartate;
Nitric oxide;
Pain measarement
- From:
Chinese Journal of Anesthesiology
1996;0(08):-
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the effects of NO synthesis inhibition on pain threshold and binding capacity of NMDA receptor of hippocampus in rats. Methods Sixty-six SD rats of both sexes weighing (210 ? 20)g were randomly divided into 11 groups of six. Group I was used for determination of baseline values of pain threshold and binding capacity of NMDA receptor. In the five L-NAME groups (group Ⅱ-Ⅵ) 1% L-NAME in normal saline 50mg?kg-1 was given intraperitoneally (IP) . In the acute experiment pain threshold was determined 15 min (group Ⅱ ) and 30 min (group Ⅲ) after L-NAME IP injection. In the chronic experiment L-NAME 50mg?kg-1 was given IP twice a day for 1 day (group Ⅳ), 4 d (group Ⅴ) and 7 d (group Ⅵ) and pain threshold was measured 12h after last L-NAME administration. Group Ⅶ-Ⅺ served as control groups in which normal saline was given IP instead of L-NAME. Pain threshold was measured by response latencies following CO2 laser stimulation which was delivered to the medial surface of the ear. After determination of pain threshold the animals were decapitated and hippocampus was removed. The binding capacity of NMDA receptor with [3H] MK-801 was determined. Bmax and KD were determined by Scatchard analysis. Results There was no significant difference in pain threshold and binding capacity of NMDA receptor between group Ⅱ ,Ⅲ (acute experiment) and their control groups ( Ⅻ,Ⅷ). In chronic experiment pain threshold significantly increased after 1 and 4 d of L-NAME administration (group Ⅳ and Ⅴ) but return to the baseline value on the 7th day. NMDA receptor binding capacity increased in all three groups of chronic experiment. Bmax was significantly higher than the baseline value on the 4th and 7th day (group Ⅴ and Ⅵ). KD was significantly higher than the baseline value on the 4th day (group Ⅴ) but returned to the baseline on the 7th day (group Ⅵ) . Conclusions In chronic experiment NO synthesis inhibition can increase pain threshold to laser thermal nociceptive stimulation and induce changes in the affinity and density of NMDA receptor.
