Analgesic effect of adenosine A_1 receptor agonist administered into the brainstem medial pontine reticular formation in rats
- VernacularTitle:脑干网状结构内注射腺苷A_1受体激动剂对大鼠的镇痛作用
- Author:
Chunsheng FENG
;
Yun YUE
;
Haichun MA
- Publication Type:Journal Article
- Keywords:
Adenosine;
Analgesia;
Brain stem;
Reticular formation
- From:
Chinese Journal of Anesthesiology
1996;0(07):-
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the analgesic effect of adenosine A1 receptor agonist R( - )-N6-(2-phenylisopropyl)-adenosine (R-PIA) administered into the brainstem medial pontine reticular formation (mPRF) and the underlying mechanism. Methods Sixty male SD rats aged 8-10 weeks weighing 250-300 g were used in this study. The animals were anesthetized with intraperitoneal 10% chloral hydrate 300 mg?kg-1 .A 24-gauge stainless steel cannula was inserted into mPRF on one side using a stereotaxic apparatus. One week after operation the animals were randomly divided into 12 groups ( n=5 each) : groupⅠcontrol; groupⅡR-PIA 0.5?g; groupⅢR-PIA 1.0?g; groupⅣR-PIA 2.0?g; groupⅤtheophylline (an adenosine receptor antagonist) 5.0?g; groupⅥ8-cyclopentyl-1 ,3-dipropylxanthine (DPCPX, an adenosine A, receptor antagonist) 1.0?g; groupⅦglibenclamide (an ATP-sensitive K+ channel blocker) 5.0?g; groupⅧ4-aminopyridine (4-AP, a voltage dependent K+-channel blocker) 5.0?g; groupⅨtheophylline 5.0?g + R-PIA 2.0?g; groupⅩDPCPX 1.0?g + R-PIA 2.0?g; groupⅪglibenclamide 5.0?g + R-PIA 2.0?g and groupⅫ4-AP 5.0?g + R-PIA 2.0?g. All the drugs were injected into mPRF in 0.3?l of normal saline. In groupⅨ-ⅫR-PIA 2.0?g was administered 15 min after pretreatment with theophylline, DPCPX, glibenclamide or 4-AP. Analgesia was determined using the tailflick latency (TFL) (the time between the onset of the radiant heat stimulus and voluntary tail withdrawal) at 5, 15, 30, 45, 60 and 90 min after R-PIA injection into mPRF. The pain threshold was expressed as percentage of the maximal possible effect ( MPE) : MPE = (TFL after drug - baseline TFL)/( 10.0 -baseline TFL)?100% .Results R-PIA 0.5-2.0?g injected into mPRF produced significant analgesia in a dose-dependent manner. Pretreatment with theophylline or DPCPX completely reversed the analgesic effect of R-PIA while pretreatment with glibenclamide or 4-AP only partially reversed the analgesic effect of R-PIA.Conclusion R-PIA administered into mPRF produces analgesia through activation of both ATP-sensitive and voltage-dependent K+ -channel in mPRF.
