Changes in the surface features of choroid plexus of the rat following the administration of acetazolamide and other drugs which affect CSF secretion.

The surface of the choroid plexus of the rat was examined by scanning electron microscopy before and after administration of acetazolamide and other drugs (cardiac glycosides and pilocarpine) which affect the rate of secretion of the CSF. In control animals, bleb-covered cells were more common on the IVth ventricle choroid plexus than on the lateral ventricle choroid plexus (20 per specimen compared to 0-3 per specimen). Following administration of acetazolamide the number of bleb-covered cells was reduced significantly (P less than 0-001). The effects of the other drugs were less well defined. Since acetazolamide is known to interfere with the active transport of the extra chloride ions normally added to the CSF in the IVth ventricle, it is suggested that the bleb-covered cells of the IVth ventricle choroid plexus are the specific site for chloride secretion.