Early weaning induces anxiety and precocious myelination in the anterior part of the basolateral amygdala of male Balb/c mice.
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.
Ono
M
M
Graduate School of Humanities and Sciences, Ochanomizu University, Bunkyo-ku, Tokyo, Japan.
Kikusui
T
T
Sasaki
N
N
Ichikawa
M
M
Mori
Y
Y
Murakami-Murofushi
K
K
D000367:Age Factors; D000679:Amygdala / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D000818:Animals; D000831:Animals, Newborn; D001007:Anxiety / Q000209:etiology* / Q000473:pathology; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D001522:Behavior, Animal; D005260:Female; D005699:Galactosylceramides / Q000378:metabolism; D050356:Lipid Metabolism; D008297:Male; D018782:Maze Learning / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009186:Myelin Sheath / Q000378:metabolism* / Q000648:ultrastructure; D012727:Sex Characteristics; D018709:Statistics, Nonparametric; D014886:Weaning
D005699:Galactosylceramides