Abnormal chloride and potassium conductances in cultured embryonic tongue muscle from trisomy 16 mouse

Trisomy 16 (Ts16) mouse is considered an animal model of Down syndrome (human trisomy 21). Whole-cell patch-clamp was used to evaluate potassium and chloride currents of cultured tongue muscle cells from fetal Ts16 and diploid mice. No difference was found in membrane capacitance between the two groups. K⁺ and Cl^- currents were pharmacologically isolated. K⁺ conductance was reduced by 31% in Ts16 cells (373 pS/pF) compared with diploid cells (539 pS/pF). Cl^- conductance was 51% larger in Ts16 cells (103 pS/pF) compared with diploid cells (68 pS/pF). However kinetics for K⁺ and Cl^- currents did not differ between the cell types. An increase in Cl^- conductance and a decrease in K⁺ conductance in Ts16 muscle cells, if present in muscle of Down syndrome subjects, might account for the observed hypotonia in these subjects. (C) 2000 Elsevier Science B.V.