颈动脉注射17β -雌二醇对去缓冲神经大鼠延髓腹外侧头端区神经元放电活动的影响

本研究旨在观察17β-雌二醇(E2)对雄性大鼠延髓腹外侧头端区(RVLM)神经元自发放电活动的影响.在切断双侧缓冲神经的麻醉雄性Sprague-Dawley大鼠上,同步记录血压、心率和RVLM神经元的自发放电活动.颈动脉内注射E2 (10 ng/kg),30个RVLM神经元自发放电单位中有25个单位的放电频率由14.46±0.47降至9.73±0.33 spikes/s (P<0.05),与此同时血压和心率无明显改变.E2的抑制效应在1 min内起效,持续时间长于5 min.雌激素受体拮抗剂tamoxifen (5 mg/kg)不能阻断E2 的抑制效应.预先给予一氧化氮(NO)合酶阻断剂L-NAME (2.7 μg/kg)能明显阻断E2的抑制效应.应用NO供体SIN-1 (0.5 μg/kg)可增强E2的抑制效应.以上结果提示,E2可通过非基因组效应激活RVLM神经元的NOS而引发NO释放,进而抑制其自发放电活动.

Effects of intracarotid injection of 17beta-estradiol on electrical activity of rostral ventrolateral medullary neurons in male rats

The purpose of this study was to determine the effects of 17beta-estradiol (E(2)) on electrical activity of the rostral ventrolateral medulla (RVLM) neurons in rats. Male Sprague-Dawley rats were anesthetized with urethane (1.0 g/kg) and subjected to sino-aortic denervation. Blood pressure, heart rate and spontaneous discharge of RVLM neurons were recorded simultaneously. Intracarotid injection of E(2) (10 ng/kg) decreased the discharge rate from 14.46+/-0.47 to 9.73+/-0.33 spikes/s (P<0.001) in 25 out of 30 RVLM neurons, while blood pressure and heart rate showed no significant change. The inhibitory effect of E(2) on RVLM neuronal activity was rapid at the onset (within 1 min) and long-lasting (>5 min). Prior administration of antiestrogen tamoxifen (TAM) did not affect the effect of E(2). However, pretreatment with N( )-nitro-L-arginine-methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase, significantly attenuated the inhibitory effect of E(2). In addition, NO donor 3-morpholinosydnonimine (SIN-1) potentiated the effect of E(2). These results suggest that E(2) may inhibit spontaneous electrical activity of RVLM neurons, an effect which is mediated by the activation of NOS with the resultant of NO release via nongenomic actions.