Early weaning induces anxiety and precocious myelination in the anterior part of the basolateral amygdala of male Balb/c mice

Neuroscience. 2008 Oct 28;156(4):1103-10. doi: 10.1016/j.neuroscience.2008.07.078. Epub 2008 Aug 22.


Weaning is one of the most important events that occur during the early stages of life. For example, precocious weaning is known to increase anxiety-related behaviors in rodents. Here, we demonstrate that in addition to increasing anxiety, early-weaning manipulations alter the accumulation of galactosylceramide, a specific myelin constituent, and the axonal structure of myelinated fibers in the amygdala of male Balb/c mice. We found that early-weaned male mice entered the open arms of an elevated plus-maze less frequently than normally weaned mice at 3 and 5 weeks of age, which indicates persistently higher anxiety levels. However, early-weaned females exhibited fewer entries into the open arms only at 5 weeks of age. Lipid analysis of mice amygdalas showed the early accumulation of galactosylceramide in early-weaned male, but not female, mice at 5 weeks. The precocious accumulation of galactosylceramide was observed only in the amygdala; galactosylceramide accumulation was not observed in the prefrontal cortex or hippocampus of early-weaned male mice. Electron microscopy showed an increase in the number and a decrease in the diameter of myelinated axons in the anterior part of the basolateral amygdala in early-weaned male mice at 5 weeks. These results suggest that the higher anxiety levels observed in early-weaned male mice could be related to precocious myelin formation in the anterior part of the basolateral amygdala.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Amygdala / metabolism*
  • Amygdala / pathology
  • Amygdala / ultrastructure
  • Animals
  • Animals, Newborn
  • Anxiety / etiology*
  • Anxiety / pathology
  • Axons / metabolism
  • Axons / ultrastructure
  • Behavior, Animal
  • Female
  • Galactosylceramides / metabolism
  • Lipid Metabolism
  • Male
  • Maze Learning / physiology
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Electron, Transmission / methods
  • Myelin Sheath / metabolism*
  • Myelin Sheath / ultrastructure
  • Sex Characteristics*
  • Statistics, Nonparametric
  • Weaning*


  • Galactosylceramides