Lincoln G A
MRC Human Reproductive Sciences Unit Centre for Reproductive Biology, 37 Chalmers Street Edinburgh EH3 9ET, UK.
Reprod Suppl. 2002;59:131-47.
Marked seasonality, responsiveness to photoperiod, diurnal behaviour, large body size, long lifespan and adaptability in captivity are characteristics that make the Soay ram a useful model for neuroendocrine research. Adult rams are routinely housed indoors under artificial lighting of alternating 16 week periods of long and short days to entrain the seasonal cycles in reproduction, growth and metabolism. The long-term cycles in individuals are monitored directly (measurements of testis diameter, androgen-dependent skin coloration, food intake, pelage moult, locomotor activity) and retrospectively (measurements of reproductive and metabolic hormone concentrations in peripheral blood). A wide spectrum of experimental procedures, including serial blood and cerebrospinal fluid (CSF) sampling with hormone or drug treatments, tissue biopsy, stereotaxic cerebral implantation and surgical lesions, not feasible in smaller species, are used to investigate the multiple interactive neuroendocrine systems regulating seasonality. The results from a recent experiment in which rams received a lesion of the caudal arcuate nucleus (caudal ARCX) or hypothalamo-pituitary disconnection (HPD) are presented to demonstrate the fidelity of long-term data derived from the Soay ram model. The results support the view that the melatonin signal that encodes photoperiod acts within the mediobasal hypothalamus to time the gonadotrophin/gonadal cycle, but acts directly within the pituitary gland to time the prolactin/pelage cycle.
明显的季节性、对光周期的反应性、昼夜行为、体型大、寿命长以及圈养适应性等特征，使得索艾羊成为神经内分泌研究的有用模型。成年公羊通常饲养在室内，处于长短交替的16周人工光照下，以同步繁殖、生长和代谢的季节性周期。直接监测个体的长期周期（测量睾丸直径、雄激素依赖性皮肤颜色、食物摄入量、换毛、运动活动），并进行回顾性监测（测量外周血中的生殖和代谢激素浓度）。一系列广泛的实验程序，包括在较小物种中不可行的激素或药物治疗下的连续血液和脑脊液（CSF）采样、组织活检、立体定向脑植入和手术损伤，被用于研究调节季节性的多个相互作用的神经内分泌系统。展示了最近一项实验的结果，在该实验中，公羊接受了尾侧弓状核（尾侧ARCX）损伤或下丘脑-垂体切断术（HPD），以证明从索艾羊模型获得的长期数据的可靠性。结果支持这样一种观点，即编码光周期的褪黑素信号在下丘脑内侧基底部起作用，以确定促性腺激素/性腺周期的时间，但在垂体腺内直接起作用，以确定催乳素/换毛周期的时间。
