Wen Jarvi C, Dhabhar Firdaus S, Prendergast Brian J
Department of Psychology and Institute for Mind and Biology, University of Chicago, Chicago, IL 60637, USA.
Horm Behav. 2007 Jan;51(1):31-9. doi: 10.1016/j.yhbeh.2006.08.001. Epub 2006 Oct 4.
Siberian hamsters (Phodopus sungorus) exhibit reproductive and immunological responses to photoperiod. Short (<10-h light/day) days induce gonadal atrophy, increase leukocyte concentrations, and attenuate thermoregulatory and behavioral responses to infection. Whereas hamster reproductive responses to photoperiod are dependent on pineal melatonin secretion, the role of the pineal in short-day induced changes in immune function is not fully understood. To examine this, adult hamsters were pinealectomized (PINx) or sham-PINx, and transferred to short days (9-h light/day; SD) or kept in their natal long-day (15-h light/day; LD) photoperiod. Intact and PINx hamsters housed in LD maintained large testes over the next 12 weeks; sham-PINx hamsters exhibited gonadal regression in SD, and PINx abolished this effect. Among pineal-intact hamsters, blood samples revealed increases in leukocyte, lymphocyte, CD62L+ lymphocyte, and T cell counts in SD relative to LD; PINx did not affect leukocyte numbers in LD hamsters, but abolished the SD increase in these measures. Hamsters were then treated with bacterial lipopolysaccharide (LPS), which induced thermoregulatory (fever), behavioral (anorexia, reductions in nest building), and somatic (weight loss) sickness responses in all groups. Among pineal-intact hamsters, febrile and behavioral responses to LPS were attenuated in SD relative to LD. PINx did not affect sickness responses to LPS in LD hamsters, but abolished the ameliorating effects of SD on behavioral responses to LPS. Surprisingly, PINx failed to abolish the effect of SD on fever. In common with the reproductive system, PINx induces the LD phenotype in most aspects of the immune system. The pineal gland is required for photoperiodic regulation of circulating leukocytes and neural-immune interactions that mediate select aspects of sickness behaviors.
西伯利亚仓鼠（Phodopus sungorus）对光周期表现出生殖和免疫反应。短日照（<10小时光照/天）会导致性腺萎缩、白细胞浓度增加，并减弱对感染的体温调节和行为反应。虽然仓鼠对光周期的生殖反应依赖于松果体褪黑素的分泌，但松果体在短日照诱导的免疫功能变化中的作用尚未完全明确。为了研究这一点，将成年仓鼠进行松果体摘除术（PINx）或假手术（sham-PINx），然后转移到短日照（9小时光照/天；SD）环境中，或保持在其出生时的长日照（15小时光照/天；LD）光周期环境中。饲养在长日照环境中的完整仓鼠和松果体摘除仓鼠在接下来的12周内睾丸保持较大；假手术的仓鼠在短日照环境中表现出性腺退化，而松果体摘除则消除了这种影响。在松果体完整的仓鼠中，血液样本显示，与长日照相比，短日照下白细胞、淋巴细胞、CD62L +淋巴细胞和T细胞计数增加；松果体摘除术不影响长日照仓鼠的白细胞数量，但消除了短日照下这些指标的增加。然后用细菌脂多糖（LPS）处理仓鼠，所有组均出现体温调节（发热）、行为（厌食、筑巢减少）和躯体（体重减轻）疾病反应。在松果体完整的仓鼠中，与长日照相比，短日照下对LPS的发热和行为反应减弱。松果体摘除术不影响长日照仓鼠对LPS的疾病反应，但消除了短日照对LPS行为反应的改善作用。令人惊讶的是，松果体摘除术未能消除短日照对发热的影响。与生殖系统一样，松果体摘除术在免疫系统的大多数方面诱导出长日照表型。松果体对于光周期调节循环白细胞以及介导疾病行为某些方面的神经-免疫相互作用是必需的。
