Mann Phyllis E, Babb Jessica A
Department of Biomedical Sciences, Tufts University School of Veterinary Medicine, 200 Westboro Road, N. Grafton, MA 01536, United States.
Brain Res. 2004 Oct 29;1025(1-2):51-8. doi: 10.1016/j.brainres.2004.07.064.
Virgin female rats do not respond maternally to foster pups due to an endogenous neural circuit that actively inhibits the display of maternal behavior. Once pregnant, primigravid rats will continue to avoid foster pups until just prior to or at parturition. Anosmia or lesions of the olfactory tract, medial amygdala, and areas of the hypothalamus will stimulate virgin females to display maternal behavior rapidly, but little is known of the effect of these lesions in primigravid rats. The objective of the present study was to determine if neurotoxic lesions of the dorsomedial (DMH) and ventromedial nuclei (VMH) of the hypothalamus will advance the onset of maternal behavior in primigravid rats. Nulliparous Sprague-Dawley female rats were mated and then on day 8 of gestation bilaterally infused with N-methyl-d-aspartic acid (NMDA; 8 microg/0.2 microl/side) or vehicle directed toward either the DMH or VMH. Beginning on day 15 of gestation until parturition, females were tested daily for maternal responsiveness. DMH and VMH lesions significantly advanced the onset of maternal behavior (5-6 days vs. 0-1 day before parturition) in first-time pregnant rats. These results indicate that the DMH and VMH are involved in the regulation of maternal behavior and may be part of an endogenous neural circuit that inhibits maternal behavior during pregnancy.
未孕雌性大鼠不会对寄养幼崽表现出母性行为，这是由于一种内源性神经回路会主动抑制母性行为的表现。一旦怀孕，初孕大鼠会继续避开寄养幼崽，直到临产前或分娩时。嗅觉缺失或嗅束、内侧杏仁核以及下丘脑区域的损伤会促使未孕雌性大鼠迅速表现出母性行为，但对于这些损伤在初孕大鼠中的影响却知之甚少。本研究的目的是确定下丘脑背内侧核（DMH）和腹内侧核（VMH）的神经毒性损伤是否会使初孕大鼠的母性行为提前出现。将未孕的斯普拉-道来雌性大鼠进行交配，然后在妊娠第8天，向双侧的DMH或VMH注入N-甲基-D-天冬氨酸（NMDA；8微克/0.2微升/侧）或溶剂。从妊娠第15天开始直至分娩，每天对雌性大鼠进行母性反应测试。DMH和VMH损伤显著提前了初孕大鼠母性行为的出现时间（分娩前5 - 6天与0 - 1天相比）。这些结果表明，DMH和VMH参与了母性行为的调节，并且可能是孕期抑制母性行为的内源性神经回路的一部分。
