Parsons Matthew P, Li Sa, Kirouac Gilbert J
Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, Newfoundland and Labrador, A1B 3V6, Canada.
Synapse. 2006 Jun 15;59(8):480-90. doi: 10.1002/syn.20264.
The paraventricular nucleus of the thalamus (PVT) receives afferents from the brainstem and has been thought to relay arousal related information to specific limbic forebrain areas, including the nucleus accumbens. More recent anatomical observations suggest that the PVT also receives afferents from various hypothalamic nuclei. The present anatomical experiments investigated the innervation of the PVT by fibers immunoreactive for orexin and cocaine and amphetamine related transcript (CART), two feeding-related peptides highly concentrated in the hypothalamus. Emphasis was placed on identifying the relationship between these neuropeptides and PVT neurons projecting to the shell of the nucleus accumbens (NacSh). Infusion of a retrograde tracer into the NacSh labeled numerous cells of the midline and intralaminar thalamus, most of which were restricted to the PVT. The retrograde tracer, orexin fibers, and CART fibers were immunopositive throughout the entire PVT whereas no overlap between signals was evident within adjacent thalamic regions. High-magnification light and confocal microscopy showed that both orexin and CART fibers made frequent contact with retrogradely labeled neurons throughout the anteroposterior PVT. Furthermore, single PVT cells retrogradely labeled from the NacSh were apposed by both orexin and CART fibers. The present experiments provide the first evidence suggesting a role for the PVT as a relay of hypothalamic activity to the nucleus accumbens. The PVT may function to link visceral arousal signals with limbic regions involved in behavioral responses.
丘脑室旁核（PVT）接收来自脑干的传入神经，一直被认为是将与觉醒相关的信息传递到包括伏隔核在内的特定边缘前脑区域。最近的解剖学观察表明，PVT也接收来自各种下丘脑核团的传入神经。本解剖学实验研究了食欲素和可卡因及苯丙胺调节转录肽（CART）免疫反应性纤维对PVT的支配，这两种与进食相关的肽高度集中在下丘脑。重点在于确定这些神经肽与投射到伏隔核壳（NacSh）的PVT神经元之间的关系。向NacSh注射逆行示踪剂标记了中线和丘脑板内核的大量细胞，其中大多数局限于PVT。逆行示踪剂、食欲素纤维和CART纤维在整个PVT中均呈免疫阳性，而在相邻丘脑区域内信号之间没有明显重叠。高倍光学显微镜和共聚焦显微镜显示，食欲素和CART纤维在整个前后PVT中都经常与逆行标记的神经元接触。此外，从NacSh逆行标记的单个PVT细胞同时被食欲素和CART纤维所包围。本实验提供了首个证据，表明PVT作为下丘脑活动向伏隔核传递的中继站发挥作用。PVT可能起到将内脏觉醒信号与参与行为反应的边缘区域联系起来的作用。
