Department of Anatomy, School of Medicine, Biomedical Science Research Building #414, Konkuk University, 143-701 Seoul, Republic of Korea.
Brain Res. 2013 Jan 15;1490:72-82. doi: 10.1016/j.brainres.2012.08.022. Epub 2012 Sep 5.
Brainstem aminergic and cholinergic nuclei are essential components of reticular activating system which are under the control of hypothalamic sleep/arousal centers. In contrast to well-known role of hypocretin (Hcrt) as a potent wake-promoting substance, only recent reports stated that melanin-concentrating hormone (MCH) plays a role in the maintenance of rapid eye movement (REM) sleep. As the sequel to our report concerning the MCH/Hcrt projection to the brainstem cholinergic nuclei (Hong et al., 2011), in the present study we examined the differential projection from MCH/Hcrt neurons in medial and lateral subdivisions of the lateral hypothalamus (LH) to the dorsal raphe (DR) or the nuclear core of the locus coeruleus (LC) of the rat. Following the injection of Red Retrobeads into the LC core (n=6), the proportions of retrogradely labeled (retro-) MCH neurons over the total retro-cells were 4.4% ± 0.5% (medial subdivision) and 7.4% ±0 .6% (lateral one), whereas those of retro-Hcrt cells over the total retro-cells were 69.4% ± 3.6% (medial) and 64.4% ± 5.2% (lateral). Following midline-DR injections (n=6), the proportions of retro-MCH neurons over the total retro-cells were 14.3% ± 2.9% (medial) and 12.3% ± 1.6% (lateral), while those of retro-Hcrt cells over the total retro-cells were 46.5% ± 6.2% (medial) and 51.3% ± 9.5% (lateral). Following lateral wing-DR injections (n=3), the proportions of retro-MCH neurons over the total retro-cells were 15.5% ± 1.2% (medial) and 11.9% ± 3.1% (lateral), while those of retro-Hcrt cells over the total retro-cells were 48.5% ± 2.7% (medial) and 52.8% ± 2.3% (lateral). The statistical analysis showed that MCH neurons projecting to the LC core or DR were outnumbered by Hcrt cells (P<0.01) and that retro-MCH cells exhibited lateral predominance in LC injection cases (P<0.05). Based on our present as well as previous (Hong et al., 2011) observations, we suggested that MCH and Hcrt neurons in the LH provide preferential projections to the brainstem cholinergic and aminergic nuclei, respectively and that MCH projections to the nuclear core of the LC exhibit differential distribution within LH subdivisions.
脑于的单胺能和胆碱能核团是网状激活系统的重要组成部分，网状激活系统受下丘脑睡眠/觉醒中枢的控制。与众所周知的下丘脑泌素（Hcrt）作为一种有效的促觉醒物质的作用相反，只有最近的报道指出黑色素浓缩激素（MCH）在维持快速眼动（REM）睡眠中起作用。作为我们关于中脑胆碱能核团内 MCH/Hcrt 投射的报告的后续（Hong 等人，2011），在本研究中，我们检查了来自内侧和外侧下丘脑（LH）的 MCH/Hcrt 神经元对背缝核（DR）或蓝斑核（LC）核心的差异投射。在将红色逆行标记物注射到 LC 核心（n=6）后，逆行标记（retro-）MCH 神经元占总逆行细胞的比例为 4.4%±0.5%（内侧部分）和 7.4%±0.6%（外侧），而逆行 Hcrt 细胞占总逆行细胞的比例为 69.4%±3.6%（内侧）和 64.4%±5.2%（外侧）。在中线-DR 注射后（n=6），逆行 MCH 神经元占总逆行细胞的比例为 14.3%±2.9%（内侧）和 12.3%±1.6%（外侧），而逆行 Hcrt 细胞占总逆行细胞的比例为 46.5%±6.2%（内侧）和 51.3%±9.5%（外侧）。在外侧翼-DR 注射后（n=3），逆行 MCH 神经元占总逆行细胞的比例为 15.5%±1.2%（内侧）和 11.9%±3.1%（外侧），而逆行 Hcrt 细胞占总逆行细胞的比例为 48.5%±2.7%（内侧）和 52.8%±2.3%（外侧）。统计分析表明，投射到 LC 核心或 DR 的 MCH 神经元数量少于 Hcrt 细胞（P<0.01），并且逆行 MCH 细胞在 LC 注射病例中表现出外侧优势（P<0.05）。基于我们目前以及之前的（Hong 等人，2011）观察结果，我们认为 LH 中的 MCH 和 Hcrt 神经元分别优先投射到脑干胆碱能和单胺能核团，并且 MCH 投射到 LC 核的核心表现出 LH 细分中的差异分布。
