Lonstein J S, Stern J M
Department of Psychology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, USA.
J Neurosci. 1997 May 1;17(9):3364-78. doi: 10.1523/JNEUROSCI.17-09-03364.1997.
the upright, crouched, or kyphotic, nursing posture of lactating rats is dependent on suckling stimulation from pups. Because of the neuroanatomical connections of the periaqueductal gray (PAG) and its sensorimotor integration of the analogous lordosis posture displayed by sexually receptive female rats, the possible role of the PAG in kyphosis was investigated using c-fos immunocytochemistry and electrolytic lesions. Lactating rats interacting with and nursing a litter of suckling pups showed greater Fos-immunoreactive nuclei in the lateral and ventrolateral caudal PAG (cPAGl,vl) compared with dams receiving nonsuckling somatosensory, distal, or no stimulation from pups. In contrast, this pattern was not evident in the rostral PAG, where the highest Fos levels occurred in nonsuckled dams, or in five other brainstem sites with either no group differences (peripenduncular, dorsal raphe, and pontine nuclei) or negligible Fos (ventral tegmental area, spinal trigeminal nuclei). After bilateral electrolytic lesions of the cPAGl,vl during gestation or on day 7 postpartum, active maternal behaviors, such as retrieval and licking of pups, and total nursing time were essentially normal. Kyphotic nursing, however, was reduced by 85%, nursing in prone and supine postures increased substantially, and 24 hr litter weight gains were reduced, particularly early in lactation (by 26%). Furthermore, lesioned rats attacked a strange male twice as often as controls did, which is suggestive of reduced fearfulness. These results extend the known roles of the PAG in reproductive and defensive behaviors to the postural control of suckling-induced kyphotic nursing and the modulation of maternal aggression.
哺乳期大鼠直立、蹲伏或驼背的哺乳姿势取决于幼崽的吮乳刺激。由于中脑导水管周围灰质（PAG）的神经解剖学连接及其与处于性接受期的雌性大鼠所表现出的类似脊柱前凸姿势的感觉运动整合，因此使用c-fos免疫细胞化学和电解损伤法研究了PAG在驼背中的可能作用。与接受来自幼崽的非吮乳体感刺激、远端刺激或无刺激的母鼠相比，与一窝吮乳幼崽互动并哺乳的哺乳期大鼠在尾侧PAG的外侧和腹外侧（cPAGl，vl）显示出更多的Fos免疫反应性细胞核。相比之下，这种模式在嘴侧PAG中并不明显，在未哺乳的母鼠中Fos水平最高，在其他五个脑干部位也没有明显差异（室周、中缝背核和脑桥核）或Fos可忽略不计（腹侧被盖区、三叉神经脊束核）。在妊娠期间或产后第7天对cPAGl，vl进行双侧电解损伤后，诸如找回和舔舐幼崽等积极的母性行为以及总哺乳时间基本正常。然而，驼背哺乳减少了85%，俯卧和仰卧姿势的哺乳大幅增加，并且24小时内幼崽体重增加减少，尤其是在哺乳期早期（减少了26%）。此外，损伤的大鼠攻击陌生雄性的频率是对照组的两倍，这表明其恐惧性降低。这些结果将PAG在生殖和防御行为中的已知作用扩展到了对吮乳诱导的驼背哺乳的姿势控制以及母性攻击的调节。
