Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo, Av. Lineu Prestes, 2415, CEP 05508-000 Sao Paulo, SP, Brazil.
Neurosci Lett. 2011 Sep 1;501(3):157-62. doi: 10.1016/j.neulet.2011.07.006. Epub 2011 Jul 18.
The dorsal premammillary nucleus (PMd) is one of the most responsive hypothalamic sites during exposure to a predator or its odor, and to a context previously associated with a predatory threat; and lesions or pharmacological inactivation centered therein severely reduced the anti-predatory defensive responses. Previous studies have shown that beta adrenergic transmission in the PMd seems critical to the expression of fear responses to predatory threats. In the present study, we have investigated the putative sources of catecholaminergic inputs to the PMd. To this end, we have first described the general pattern of catecholaminergic innervation of the PMd by examining the distribution and morphology of the tyrosine hydroxylase (TH) immunoreactive fibers in the nucleus; and next, combining Fluoro Gold (FG) tracing experiments and TH immunostaining, we determined the putative sources of catecholaminergic inputs to the nucleus. Our results revealed that the PMd presents a moderately dense plexus of catecholaminergic fibers that seems to encompass the rostral pole and ventral border of the nucleus. Combining the results of the FG tract-tracing and TH immunostaining, we observed that the locus coeruleus was the sole brain site that contained double FG and TH immunostained cells. In summary, the evidence suggests that the locus coeruleus is seemingly a part of the circuit responding to predatory threats, and, as shown by the present results, is the sole source of catecholaminergic inputs to the PMd, providing noradrenergic inputs to the nucleus, which, by acting via beta adrenoceptor, seems to be critical for the expression of anti-predatory responses.
背侧前乳头体核（PMd）是在暴露于捕食者或其气味以及与先前与捕食威胁相关联的环境中最敏感的下丘脑部位之一；而其中央的损伤或药理学失活严重降低了抗捕食防御反应。先前的研究表明，PMd 中的β肾上腺素能传递对于对捕食威胁的恐惧反应的表达似乎至关重要。在本研究中，我们研究了 PMd 中儿茶酚胺能传入的假定来源。为此，我们首先通过检查核内酪氨酸羟化酶（TH）免疫反应纤维的分布和形态，描述了 PMd 的儿茶酚胺能传入的一般模式；接下来，结合氟金（FG）示踪实验和 TH 免疫染色，我们确定了核内儿茶酚胺能传入的假定来源。我们的结果表明，PMd 具有中等密度的儿茶酚胺能纤维丛，似乎包含核的喙状突和腹侧边界。结合 FG 束追踪和 TH 免疫染色的结果，我们观察到蓝斑是唯一包含双 FG 和 TH 免疫染色细胞的脑区。总之，证据表明蓝斑似乎是对捕食威胁做出反应的回路的一部分，并且，如本结果所示，是 PMd 中儿茶酚胺能传入的唯一来源，为核提供去甲肾上腺素能传入，通过β肾上腺素能受体起作用，对于抗捕食反应的表达似乎至关重要。
