title: Localization of p450scc and 5alpha-reductase type-2 in the cerebellum of fetal and newborn sheep.
abstract: Prenatally, neuroactive steroids that modulate GABAergic activity may be synthesized de novo within the fetal brain. We have examined changes in immunoreactivity staining for the steroidogenic enzymes cholesterol P450 side-chain cleavage (P450scc), and 5alpha-reductase type-2 in the cerebellum of late gestation (130-145 days gestation) fetal sheep and newborn lambs (1-4 weeks of age). Both enzymes were predominantly localized in the Purkinje cell body and dendrites of the fetal and newborn cerebellum, with weaker immunoreactivity in a few cells of the inner granular layer. P450scc immunoreactivity was present in Purkinje neurons expressing either of the neuronal microtubule associated proteins MAP1b/5 or MAP2a/b, but was absent from GFAP and HNK-1 positive cells. Soma of Purkinje neurons were also immunopositive for 5alpha-reductase type-2 in the fetuses, but expression decreased to just detectable levels in the 1-2 and 2-4 week old lambs. Both MAP1b/5- and MAP2a/b-positive Purkinje neurons showed 5alpha-reductase type-2 expression in the fetus, whereas the residual 5alpha-reductase staining in the newborn lamb was present only in MAP2a/b-positive Purkinje neurons. Allopregnanolone in the cerebellum decreased from 21.8+/-1.9 ng/g wet weight in fetuses at 140-145 days gestation to 6.7+/-0.5 ng/g in 2-4 week old lambs (P<0. 05). Thus, synthesis of neuroactive steroids from cholesterol is possible in cerebellar neurons in late gestation and persists into neonatal life, 5alpha-reductase type-2 expression is greater in the fetus compared to the neonate, and allopregnanolone concentrations in the cerebellum decrease significantly after birth.
authors.affiliation: Department of Physiology, Monash University, Victoria 3800, Clayton, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Petratos
authors.forename: J J
authors.initials: JJ
authors.lastname: Hirst
authors.forename: S
authors.initials: S
authors.lastname: Mendis
authors.forename: P
authors.initials: P
authors.lastname: Anikijenko
authors.forename: D W
authors.initials: DW
authors.lastname: Walker
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D002531:Cerebellum / Q000166:cytology / Q000196:embryology* / Q000201:enzymology*; D042944:Cholestenone 5 alpha-Reductase; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D010088:Oxidoreductases / Q000378:metabolism*; D011247:Pregnancy; D011280:Pregnanolone / Q000494:pharmacology; D011689:Purkinje Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D011963:Receptors, GABA-A / Q000378:metabolism; D012756:Sheep
chemical_list: D011963:Receptors, GABA-A; D011280:Pregnanolone; D010088:Oxidoreductases; D002786:Cholesterol Side-Chain Cleavage Enzyme; D042944:Cholestenone 5 alpha-Reductase