A specific taurine recognition site in the rabbit brain is responsible for taurine effects on thermoregulation
作者:Maria Frosini、Casilde Sesti、Simona Saponara、Lorenzo Ricci、Massimo Valoti、Mitri Palmi、Fabrizio Machetti、Giampietro Sgaragli
DOI:10.1038/sj.bjp.0705274
日期:2003.6
Taurine and GABA are recognized as endogenous cryogens. In a previous study, some structural analogues of taurine, namely 6‐aminomethyl‐3‐methyl‐4H‐1,2,4‐benzothiadiazine 1,1‐dioxide (TAG), 2‐aminoethylarsonic (AEA), 2‐hydroxyethanesulfonic (ISE) and (±)cis‐2‐aminocyclohexane sulfonic acids (CAHS) have been shown to displace [3H]taurine binding from rabbit brain synaptic membrane preparations, without interacting either with GABA‐ergic systems, nor with taurine uptake mechanism, thus behaving like direct taurinergic agents.
To answer the question whether the role of taurine as an endogenous cryogen depends on the activation of GABA receptors or that of specific taurine receptor(s), taurine or the above structural analogues were injected intracerebroventricularly in conscious, restrained rabbits singularly or in combination and their effects on rectal (RT)‐ and ear–skin temperature and gross motor behavior (GMB) were monitored.
Taurine (1.2 × 10−6–4.8 × 10−5 mol) induced a dose‐related hypothermia, vasodilation at ear vascular bed and inhibition of GMB. CAHS, at the highest dose tested (4.8 × 10−5 mol) induced a taurine‐like effect either on RT or GMB. On the contrary ISE, injected at the same doses of taurine, induced a dose‐related hyperthermia, vasoconstriction and excitation of GMB. AEA and TAG caused a dose‐related hyperthermia, but at doses higher than 1.2 × 10−7 mol caused death within 24 h after treatment.
CAHS (4.8 × 10−5 mol) antagonized the hyperthermic effect induced by TAG (1.2 × 10−6 mol), AEA (1.2 × 10−8 mol) or ISE (4.8 × 10−5 mol).
In conclusion, these findings may indicate the existence of a recognition site specific for taurine, responsible for its effects on thermoregulation.
British Journal of Pharmacology (2003) 139, 487–494. doi:10.1038/sj.bjp.0705274
牛磺酸和γ-氨基丁酸(GABA)被认可为内源性低温剂。在之前的实验中,发现了一些牛磺酸的结构类似物,包括6-氨基甲基-3-甲基-4H-1,2,4-苯并噻二嗪1,1二氧化物(TAG)、2-氨基乙基砷酸(AEA)、2-羟基乙烷磺酸(ISE)以及(±)-顺式-2-氨基环己烷磺酸(CAHS),这些化合物能够取代兔脑突触膜制备物中[3H]牛磺酸的结合位点,而不会与GABA系统或牛磺酸摄取机制发生相互作用,因而表现出直接的牛磺酸样作用。
为了探讨牛磺酸作为内源性低温剂的作用是否依赖于GABA受体的激活,或是特定的牛磺酸受体的激活,实验将牛磺酸或上述结构类似物单独或联合注入正常、束缚兔的脑室,观察其对肛门(RT)和耳部皮肤温度以及粗大运动行为(GMB)的影响。
实验结果显示,牛磺酸(1.2×10−6–4.8×10−5 mol)引起剂量相关的体温下降、耳部血管扩张和GMB抑制。CAHS在最高剂量(4.8×10−5 mol)时表现出与牛磺酸相似的对RT和GMB的影响。相反地,ISE在与牛磺酸相同剂量下引起剂量相关的体温上升、血管收缩和GMB兴奋。AEA和TAG引起剂量相关的体温上升,但剂量高于1.2×10−7 mol时,导致给药后24小时内死亡。
CAHS(4.8×10−5 mol)能够拮抗TAG(1.2×10−6 mol)、AEA(1.2×10−8 mol)或ISE(4.8×10−5 mol)引起的体温上升效应。
综上所述,这些研究结果可能表明存在一个特异性识别牛磺酸的结合位点,负责其对体温调节的作用。
《英国药理学杂志》(2003)139, 487–494. doi:10.1038/sj.bjp.0705274.