Yue J L, Goshima Y, Miyamae T, Misu Y
Department of Pharmacology, Yokohama City University School of Medicine, Japan.
Brain Res. 1993 Dec 3;629(2):310-4. doi: 10.1016/0006-8993(93)91336-q.
By microdialysis in the rostral ventrolateral medulla (RVLM) of anesthetized rats, the spontaneous L-3,4-dihydroxyphenylalanine (DOPA) release was partially Ca(2+)-dependent and tetrodotoxin-sensitive and was markedly reduced by alpha-methyl-p-tyrosine (alpha-MPT; 200 mg/kg, i.p.). K+ (50 mM) Ca(2+)-dependently evoked L-DOPA. By microinjections into unilateral RVLM, L-DOPA (30-300 ng) produced dose-dependent hypertension and tachycardia similarly in rats untreated, treated with i.p. 3-hydroxybenzylhydrazine, a central DOPA decarboxylase inhibitor, or with i.v.t. 6-hydroxydopamine. These responses were antagonized by L-DOPA methyl ester (1.5 micrograms), a competitive L-DOPA antagonist. D-DOPA, dopamine, noradrenaline or adrenaline (300 ng) produced no effect. Furthermore, L-DOPA methyl ester alone microinjected into bilateral RVLM (2 micrograms x 2) produced prolonged hypotension and bradycardia, which were abolished by alpha-MPT. These data suggest that L-DOPA is relevant to modulation of sympathetic activity in the rat RVLM.
通过对麻醉大鼠延髓头端腹外侧区（RVLM）进行微透析发现，L-3,4-二羟基苯丙氨酸（DOPA）的自发释放部分依赖于Ca(2+)且对河豚毒素敏感，并且可被α-甲基对酪氨酸（α-MPT；200毫克/千克，腹腔注射）显著降低。50毫摩尔/升的K+以Ca(2+)依赖的方式诱发L-DOPA释放。通过向单侧RVLM微量注射，L-DOPA（30 - 300纳克）在未处理的大鼠、腹腔注射中枢多巴脱羧酶抑制剂3-羟基苄基肼处理的大鼠或静脉注射6-羟基多巴胺处理的大鼠中，同样产生剂量依赖性的高血压和心动过速。这些反应可被竞争性L-DOPA拮抗剂L-DOPA甲酯（1.5微克）拮抗。D-DOPA、多巴胺、去甲肾上腺素或肾上腺素（300纳克）无作用。此外，单独向双侧RVLM微量注射L-DOPA甲酯（2微克×2）会产生持续的低血压和心动过缓，而α-MPT可消除这些现象。这些数据表明L-DOPA与大鼠RVLM中交感神经活动的调节有关。
