Heterotypic sprouting of serotonergic forebrain fibers in the brindled mottled mutant mouse.
The brindled mottled mouse has a mutation on the X-chromosome which causes alterations in copper metabolism. One role for copper is as a cofactor for dopamine-beta-hydroxylase (DBH), the enzyme that converts dopamine to norepinephrine (NE). This may explain the fact that the hemizygous males have low concentrations of NE, as well as high concentrations of 5-hydroxyindoleacetic acid (5-HIAA) in the brainstem and forebrain. The present study quantified serotonin (5-HT) immunoreactive fibers in the cerebral cortex and striatum of hemizygous males and control littermates on postnatal (P) days 7, 10, 12 and 14. The density of 5-HT immunoreactive fibers was measured using a digitized imaging system in conjunction with darkfield microscopy. Measurements of 5-HT innervation showed an age-dependent increase in density of 5-HT immunoreactive fibers in all layers of the cerebral cortex, with fiber density in brindled mice approximately 70% greater than controls by P14. High performance liquid chromatography confirmed the increased concentrations of 5-HT and 5-HIAA, and the low concentration of NE, in several regions. We believe that these results are an example of heterotypic sprouting of 5-HT neurons, similar to that observed in neonatal rats given 6-hydroxydopamine (6-OHDA). If so, these data provide the first description of 5-HT heterotypic sprouting in mice, and the first description of 5-HT heterotypic sprouting resulting from a natural disease state, rather than an experimentally induced lesion.
Martin
P
P
Department of Pathology, University of North Carolina, Chapel Hill 27599.
Ohno
M
M
Southerland
S B
SB
Mailman
R B
RB
Suzuki
K
K
D000818:Animals; D001933:Brain Stem / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000196:embryology / Q000254:growth & development; D002851:Chromatography, High Pressure Liquid; D005260:Female; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008818:Mice, Neurologic Mutants; D009412:Nerve Fibers / Q000502:physiology*; D011247:Pregnancy; D016548:Prosencephalon / Q000166:cytology* / Q000254:growth & development* / Q000378:metabolism; D012701:Serotonin / Q000502:physiology*
D012701:Serotonin