Bealer S L, Crowley W R
Department of Physiology, University of Tennessee, Memphis 38163, USA.
Am J Physiol. 1998 Mar;274(3):E453-8. doi: 10.1152/ajpendo.1998.274.3.E453.
Noradrenergic systems regulate the systemic release of oxytocin (OT) in lactating rats. However, a role for norepinephrine (NE) in release of OT within the magnocellular nuclei during suckling has not been established. These studies were designed to determine 1) if suckling induces NE release in the supraoptic (SON) and paraventricular (PVN) nuclei of conscious rats and 2) the role of NE in the central, intranuclear release of OT within these nuclei. Female Holtzman rats were implanted with microdialysis probes adjacent to the PVN or SON on lactation days 8-12. The following day, the pups were isolated from the dams for 4 h. Microdialysis probes were perfused with artificial cerebrospinal fluid (ACSF) or with ACSF containing an alpha- or a beta-adrenergic receptor antagonist. Dialysate was collected before, during, and after suckling and analyzed for NE or OT. In an additional experiment, an alpha- or beta-adrenergic agonist was administered via the microdialysis probes into the PVN in nonsuckled, lactating rats. Extracellular NE increased in the PVN during suckling but was not detectable in the SON. OT concentrations in dialysates from the PVN and SON significantly increased during suckling. Blockade of either alpha-(in both PVN and SON) or beta- (PVN) adrenergic receptors prevented the suckling-induced increase in central OT release. OT release was increased in nonsuckled, lactating rats by central application of either an alpha- or beta-adrenergic agonist. These data demonstrate that intranuclear NE release is increased in the PVN by suckling and that subsequent stimulation of both alpha- and beta-noradrenergic receptors mediates intranuclear OT release.
去甲肾上腺素能系统调节泌乳大鼠体内催产素（OT）的全身释放。然而，去甲肾上腺素（NE）在哺乳期间大细胞神经核团内OT释放中的作用尚未明确。这些研究旨在确定：1）哺乳是否会诱导清醒大鼠视上核（SON）和室旁核（PVN）中NE的释放；2）NE在这些核团内OT的中枢性、核内释放中的作用。在泌乳第8 - 12天，将雌性霍尔茨曼大鼠植入靠近PVN或SON的微透析探针。次日，将幼崽与母鼠分离4小时。微透析探针用人工脑脊液（ACSF）或含α-或β-肾上腺素能受体拮抗剂的ACSF灌注。在哺乳前、哺乳期间和哺乳后收集透析液，分析其中的NE或OT。在另一项实验中，通过微透析探针向未哺乳的泌乳大鼠PVN内注射α-或β-肾上腺素能激动剂。哺乳期间PVN中的细胞外NE增加，但在SON中未检测到。PVN和SON透析液中的OT浓度在哺乳期间显著增加。α-肾上腺素能受体阻断剂（在PVN和SON中均有作用）或β-肾上腺素能受体阻断剂（在PVN中）均可阻止哺乳诱导的中枢OT释放增加。通过向未哺乳的泌乳大鼠中枢应用α-或β-肾上腺素能激动剂可增加OT释放。这些数据表明，哺乳可使PVN内核内NE释放增加，随后α-和β-去甲肾上腺素能受体的刺激均介导核内OT释放。
