FUNCTIONAL OPENING OF THE 4TH VENTRICULAR OUTLET IN C57BL 6J AND DELAYED SPLOTCH MOUSE EMBRYOS/

To compare the functional development of the fourth ventricular outlet in the myeloschisis-Chiari malformation complex with that of a normal brain, the chronological development of the outlet in C57BL/6J non-ne ural-tube defect mouse embryos was examined as the first step, Then we compared the results with those of homozygotic delayed splotch (Spd) mouse embryos which had neural-tube defects (NTDs). Ferrous chloride ( Prussian blue) solution was injected into the lateral or mesencephalic ventricle on gestation days 13-16 in the case of control C57BL/6J mou se embryos and on gestation days 14-16 in the case of homozygotic Spd mouse embryos which had open spinal NTDs and hindbrain anomalies compa rable to human Chiari malformation, At 30 min after the injection, aci d fixative was infused through the heart to set off the Prussian blue reaction, which makes the dye visible by the precipitation of ferric c hloride, According to the present method, more than 75% of C57BL/6J mo use (non-NTD control) embryos showed the evidence of function of the f ourth ventricular (4V) outlet from gestation day 15. It was difficult to apply the same method to Spd mouse embryos with NTDs due to the sma ll size of ventricles. Only 4 injections were successful, of which 3 s howed the functioning evidence of the 4V outlet, Though the number of mouse embryos with NTDs studied was small, the results suggest that th e chronological progress of functional opening of the fourth ventricle in mouse embryos with NTDs is similar to that of control non-NTD embr yos.