Li C, Chen P, Smith M S
Division of Neuroscience, Oregon Regional Primate Research Center, Department of Physiology and Pharmacology, Oregon Health Sciences University, 505 NW 185th Avenue, Beaverton, OR 97006, USA.
Brain Res. 1999 Apr 10;824(2):267-76. doi: 10.1016/s0006-8993(99)01217-2.
Activation of the neuropeptide Y (NPY) neuronal system in the arcuate nucleus of the hypothalamus (ARH) during lactation in the rat is likely due to the neural impulses arising from the suckling stimulus. However, the afferent neuronal input to the ARH that is activated during lactation and is responsible for activation of NPY neurons is currently unknown. Previously, using cFos as a marker for neuronal activation, we identified several brain areas in the lactating animals that were activated by the suckling stimulus. Thus, the objective of the present study was to determine if these activated areas observed in the lactating animals project directly into the ARH. The retrograde tracer, fluorogold (FG), was injected into the ARH on day 4 postpartum. Chronically suckled rats were then deprived of their eight-pup litters on day 9 postpartum, and 48 h later, the pups were returned to the females to reinitiate the suckling stimulus for 90 min to induce cFos expression. The animals were then perfused and the brains were subjected to double-label immunohistochemistry to visualize both FG- and cFos-positive cells. Substantial FG/cFos double-labeled cells were found in forebrain regions, including the medial preoptic area, periventricular preoptic area, bed nucleus of the stria terminalis, and the medial amygdala, and in brainstem regions including the lateral parabrachial nucleus, peripeduncular area and ventrolateral medulla. The results of the present study demonstrate that specific areas in the brain are activated during lactation and send direct projections to the ARH. Thus, these areas are potentially important candidates for mediating the activation of the NPY neuronal system in the ARH during lactation.
在大鼠哺乳期，下丘脑弓状核（ARH）中神经肽Y（NPY）神经元系统的激活可能是由于哺乳刺激产生的神经冲动所致。然而，目前尚不清楚在哺乳期被激活并负责激活NPY神经元的ARH传入神经元输入是什么。此前，我们使用cFos作为神经元激活的标志物，在哺乳期动物中鉴定出了几个被哺乳刺激激活的脑区。因此，本研究的目的是确定在哺乳期动物中观察到的这些激活区域是否直接投射到ARH。在产后第4天，将逆行示踪剂荧光金（FG）注入ARH。然后，在产后第9天，将长期哺乳的大鼠与它们的八只幼崽分开，48小时后，将幼崽放回母鼠身边，重新开始90分钟的哺乳刺激以诱导cFos表达。然后对动物进行灌注，并对大脑进行双重标记免疫组织化学，以观察FG和cFos阳性细胞。在前脑区域，包括内侧视前区、室周视前区、终纹床核和内侧杏仁核，以及脑干区域，包括外侧臂旁核、脚周区和延髓腹外侧，发现了大量FG/cFos双重标记细胞。本研究结果表明，大脑中的特定区域在哺乳期被激活，并直接投射到ARH。因此，这些区域可能是介导哺乳期ARH中NPY神经元系统激活的重要候选区域。
