Kim Y I, Dudley C A, Moss R L
Department of Physiology, University of Texas, Southwestern Medical Center, Dallas 75235-9040.
Synapse. 1989;3(3):213-24. doi: 10.1002/syn.890030307.
The role of norepinephrine (NE) in controlling the single-unit activity of paraventricular (PVN) neurons projecting to or passing through the caudal ventrolateral medulla (CVLM) was investigated in adult male rats anesthetized with urethane. Of 72 PVN neurons studied, 19 were antidromically activated by CVLM stimulation (Group I) and 48 were antidromically activated by posterior pituitary (PP) stimulation (Group II). The remaining 5 neurons were antidromically driven by both CVLM and PP stimulation (Group III). In 14 of the 19 Group I neurons and in all the 5 Group III neurons, iontophoretically applied NE was demonstrated to be inhibitory to the single-unit activity. No excitatory effect of NE was observed. In contrast, both excitatory and inhibitory actions of NE were observed in the Group II neurons. Of 37 Group II neurons tested, 28 were excited and 7 were inhibited by NE. The inhibitory effect of NE in Group I and Group III neurons was selectively blocked by the alpha antagonist, phentolamine, that was coiontophoresed with NE, but not by the beta antagonist, timolol (n = 9). The unit activity of Group I neurons that were inhibited by NE was not altered by an increase in arterial blood pressure (n = 3), whereas the unit activity of one NE-insensitive Group I neuron was decreased by an increase in blood pressure. Taken together, the results suggest that NE plays an alpha-adrenoreceptor-mediated inhibitory role in controlling the single-unit activity of caudally projecting PVN neurons. These neurons include a subpopulation of PVN neurons that project caudally as well as to the PP. The possible function associated with the NE-sensitive, caudally projecting PVN neurons may be other than the regulation of blood pressure.
在使用乌拉坦麻醉的成年雄性大鼠中，研究了去甲肾上腺素（NE）在控制投射至或穿过尾侧腹外侧延髓（CVLM）的室旁核（PVN）神经元单单位活动中的作用。在所研究的72个PVN神经元中，19个可被CVLM刺激逆向激活（I组），48个可被垂体后叶（PP）刺激逆向激活（II组）。其余5个神经元可被CVLM和PP刺激共同逆向驱动（III组）。在I组的19个神经元中的14个以及所有5个III组神经元中，离子电泳施加的NE被证明对单单位活动具有抑制作用。未观察到NE的兴奋作用。相比之下，在II组神经元中观察到了NE的兴奋和抑制作用。在测试的37个II组神经元中，28个被NE兴奋，7个被NE抑制。NE在I组和III组神经元中的抑制作用被与NE共同离子电泳的α拮抗剂酚妥拉明选择性阻断，但未被β拮抗剂噻吗洛尔阻断（n = 9）。被NE抑制的I组神经元的单位活动不会因动脉血压升高而改变（n = 3），而一个对NE不敏感的I组神经元的单位活动会因血压升高而降低。综上所述，结果表明NE在控制尾侧投射的PVN神经元单单位活动中发挥α-肾上腺素能受体介导的抑制作用。这些神经元包括尾侧投射以及投射至PP的PVN神经元亚群。与NE敏感的、尾侧投射的PVN神经元相关的可能功能可能不是调节血压。
