Localization of p450scc and 5alpha-reductase type-2 in the cerebellum of fetal and newborn sheep.
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.
Petratos
S
S
Department of Physiology, Monash University, Victoria 3800, Clayton, Australia.
Hirst
J J
JJ
Mendis
S
S
Anikijenko
P
P
Walker
D W
DW
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
D011963:Receptors, GABA-A; D011280:Pregnanolone; D010088:Oxidoreductases; D002786:Cholesterol Side-Chain Cleavage Enzyme; D042944:Cholestenone 5 alpha-Reductase