Stimulatory effects of melatonin on ependymal epithelium of choroid plexuses in Golden Hamsters

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Abstract
Ependymal epithelial cells from the choroid plexuses (CPs) separately of lateral (I+II), IIIrd and IVth ventricles of male Golden Hamsters were studied by electron microscopy and morphometry. The 16 hamsters were distributed between three injection groups: vehicle only, 25μg and 2500μg melatonin (M) by subcutaneous injection daily at L11 to L11.75 in a LD 14∶10 daily photoperiod. After 28 consecutive daily injections, animals were killed and the CPs were dissected, fixed and prepared for electronmicroscopy. Thirteen measures of the CP ependymal cells were made, by planimetry, morphometry or direct counting or linear measurement on the EM prints. Effects of melatonin occurred only on the cells from the lateral ventricles. Here M at high dosage caused cell swelling (averaging 50% increase in area), and other cellular changes were graded in relation to M dosage. These were increase (to 26 %) in mitochondrial area per cell, and increase (to 50 %) in length of apical microvilli. Since in other work the latter form a major locus of ouabain-sensitive Na+, K+-ATPase, it is suggested that M may possibly have a stimulatory effect on transport and related CSF secretory activities by these cells.