Ion channels in epithelial cells of the choroid plexus isolated from the lateral ventricle of rat brain.

Whole-cell patch clamp methods were used to determine the expression of ion channels in the epithelial cells of choroid plexus isolated from the lateral ventricle of the rat brain. A single population of cells with a mean capacitance of 61.5+/-1.7 pF was identified in 103 recordings. This value is significantly greater than that measured for cells from the fourth ventricle (P<0.01 by unpaired t-test), indicating that cells from the lateral ventricle have a greater surface area. Voltage-dependent, outward currents were recorded using a K(+)-rich electrode solution. These currents were partially inhibited by 10 nM margatoxin or 10 nM dendrotoxin-K and blocked by 5 mM TEA(+). An inward-rectifying chloride conductance was observed in K(+)-free solutions. The relative permeability of this conductance to anions was P(I)>P(Cl)>P(aspartate). A volume-sensitive anion conductance was observed when cell swelling was induced using a hypertonic electrode solution. The properties of each conductance were similar to conductances previously identified in fourth ventricle choroid plexus cells. Furthermore, there were no significant differences between the magnitudes of any of the conductances in cells from the lateral and fourth ventricle choroid plexus. Thus, the ionic conductances expressed in rat lateral and fourth ventricle choroid plexus are very similar.