Alcohol deters the outgrowth of serotonergic neurons at midgestation.
We have previously demonstrated that treatment of pregnant C57BL mice from gestation days 8 to 14 with alcohol with 20% ethanol-derived calories (EDC) reduced the number of serotonin (5-HT) neurons and retarded their migration in the fetal brains. In the present study, we obtained similar results with the use of 25% EDC and extended our previous findings by demonstrating that besides the alteration of the number of 5-HT neurons, prenatal alcohol exposure also affects their projecting fibers in their early development. Pregnant C57BL mice were divided into an alcohol-exposed (ALC) group given 25% EDC (4.49%, v/v), a pair-fed group to the ethanol-fed group (PF) and a chow-fed group (Chow). The PF and Chow groups served as controls. Our results showed that in the ALC group, when compared with the control groups, prenatal alcohol exposure with 25% EDC reduced the number of 5-HT-immunoreactive neurons in both the median and dorsal raphe, and the amount of 5-HT-immunoreactive fibers in the medial forebrain bundle (MFB). The diameter of the 5-HT-immunoreactive MFB was also reduced as a result of treatment. No significant differences of the above parameters were found between the PF and Chow groups. The previous and present work confirmed that alcohol reduces the normal formation and growth of 5-HT neurons in the midbrain. Furthermore, the projection of 5-HT fibers, in density as well as in distribution, is reduced in the major trajectory bundle. This may affect the amount of 5-HT fibers available to the forebrain. In light of the importance of the 5-HT system in brain development, alcohol may affect the growth of the forebrain through its effect on 5-HT signaling.
Sari
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Department of Anatomy and Cell Biology, Indiana University School of Medicine, 65 Barnhill Drive, Indianapolis, IN 46202, USA.
Powrozek
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Zhou
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D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004622:Embryo, Mammalian / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D000431:Ethanol / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D063647:Fetal Alcohol Spectrum Disorders / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D005865:Gestational Age; D007150:Immunohistochemistry; D008297:Male; D008474:Medial Forebrain Bundle / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000737:chemistry / Q000187:drug effects* / Q000473:pathology; D011247:Pregnancy; D011903:Raphe Nuclei / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D012701:Serotonin / Q000276:immunology / Q000378:metabolism*
D012701:Serotonin; D000431:Ethanol