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Neonatal maternal separation increases microglial activation in brainstem regions controlling the laryngeal chemoreflex
Author(s) -
Baldy Cécile,
BoisjolyVilleneuve Samuel,
Fournier Stéphanie,
Tremblay MarieÈve,
Kinkead Richard
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.991.2
Subject(s) - microglia , brainstem , dorsal motor nucleus , biology , immunostaining , medicine , neuroscience , anatomy , pathology , vagus nerve , immunohistochemistry , inflammation , stimulation
Laryngeal chemoreflex (LCR) is immature in preterm infants and results in prolonged apneas, O 2 desaturations and bradycardias. Previous work from our laboratory has shown that in newborn rat, neonatal maternal separation (NMS) interferes with LCR development and aggravates cardio‐respiratory complications. This effect was more important in males. Microglia are the immune cells of the central nervous system; during early life, they contribute to brain development by playing an important role in synaptic pruning. These cells are activated during stress and their activation is characterized by morphological changes. Indeed, activated microglia are more round (ameboid shaped) with short and few processes like macrophages, whereas inactivated microglia have several ramified processes scanning for abnormal cells and contacting synapses. Because neonatal stress (in the form of NMS) affects LCR development, we hypothesised that NMS increases microglial activation in regions which are involved in the LCR, particularly the nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus nerve (NX). Rat pups were separated from their mother 3 hours each day during 10 days from post‐natal day 3 to 12 (P3 to P12). Control animals were left undisturbed. At post‐natal days 14–15, brains were harvested for Iba‐1 immunostaining. Microglia were counted in the NTS and NX by light microscopy. Cell morphology was assessed in each microglia by measuring morphological index (ratio between cell body and arborisation areas), cell density and scattering (nearest neighbour distance) in NTS and NX. Stress increase significantly morphological index in both region of interest and in males and females. NMS increases microglia density in males in NTS and NX. Stress increases also microglial scattering in the N10 but this effect is significant only on P15 males and females. We conclude that NMS elicits microglial activation in the NTS and NX in a sex‐dependent fashion. Based on these morphological changes we propose that NMS may interfere with microglia's ability to perform synaptic pruning during early life. This, in turn may contribute to abnormal LCR function in pups. Support or Funding Information This research was supported by CIHR (RK).