Cline Mark A, Nandar Wint, Bowden Christie, Hein Pyae Phyo, Denbow D Michael, Siegel Paul B
Department of Biology, Radford University, Radford, VA 24142, USA.
Life Sci. 2008 Aug 1;83(5-6):208-13. doi: 10.1016/j.lfs.2008.06.003. Epub 2008 Jun 17.
This study was conducted to compare the effects of central alpha-MSH, a potent anorexigenic signal, in lines of chickens that have undergone long-term divergent selection for low (LWS) or high (HWS) body weight. Chicks from both lines were centrally injected with 0, 24, 120 or 600 pmol alpha-MSH and feed and water intake were concurrently measured thereafter for a total of 180 min. The LWS line responded to all doses of alpha-MSH with a similar potent decrease in feed intake at all observation times. The HWS line only responded to 600 pmol alpha-MSH with decreased feed intake. alpha-MSH did not influence water intake in either line. To determine if differential hypothalamic signaling was associated with the anorexigenic effect, c-Fos immunoreactivity was measured in appetite-related hypothalamic nuclei after 600 pmol central alpha-MSH injections. c-Fos immunoreactivity was increased in the dorsomedial hypothalamus, paraventricular nucleus (PVN) and ventromedial hypothalamus in both lines after alpha-MSH; however, the magnitude of increase was greater in LWS than in HWS chicks at the PVN (136% vs. 47% increase over controls, respectively). Based on behavior observations, the number of feeding and exploratory pecks is decreased with greater magnitude after alpha-MSH in the LWS line. Additionally, alpha-MSH was associated with increased deep rest in both lines, and may be a secondary effect to reduced ingestion. These data support that the LWS line has a lower threshold for the anorexigenic effect of central alpha-MSH while in the HWS line this threshold is higher, and that this difference may be associated with differential hypothalamic signaling. Genetic variation exists in the threshold of anorexigenic response for central alpha-MSH in LWS and HWS lines of chickens with possible implications to other species including humans.
本研究旨在比较中枢α-促黑素（一种有效的食欲抑制信号）对长期进行低体重（LWS）或高体重（HWS）差异选择品系鸡的影响。来自两个品系的雏鸡分别接受0、24、120或600 pmol α-促黑素的中枢注射，随后同时测量180分钟内的采食量和饮水量。LWS品系对所有剂量的α-促黑素均有反应，在所有观察时间点采食量均显著下降。HWS品系仅对600 pmol α-促黑素产生反应，采食量下降。α-促黑素对两个品系的饮水量均无影响。为了确定下丘脑信号差异是否与食欲抑制作用相关，在注射600 pmol中枢α-促黑素后，检测与食欲相关的下丘脑核团中的c-Fos免疫反应性。注射α-促黑素后，两个品系的下丘脑背内侧核、室旁核（PVN）和下丘脑腹内侧核中的c-Fos免疫反应性均增加；然而，PVN中LWS品系的增加幅度大于HWS品系（分别比对照组增加136%和47%）。基于行为观察，LWS品系在注射α-促黑素后，啄食和探索性啄食的次数下降幅度更大。此外，α-促黑素与两个品系的深度休息增加有关，可能是摄食减少的继发效应。这些数据表明，LWS品系对中枢α-促黑素食欲抑制作用的阈值较低，而HWS品系的阈值较高，这种差异可能与下丘脑信号差异有关。鸡的LWS和HWS品系对中枢α-促黑素的食欲抑制反应阈值存在遗传变异，这可能对包括人类在内的其他物种具有潜在影响。
