A CHLORIDE CHANNEL RECONSTITUTED FROM FETAL-RAT BRAIN GROWTH CONES

Chloride channels were reconstituted into planar lipid bilayers isolat ed from a preparation of growth cone particles (GCPs) isolated from fe tal rat brain. One type of channel was predominantly seen and some of its biophysical and pharmacological properties were studied. The singl e channel i-V relationship was curvilinear with a chord conductance of 75 pS at +30 mV in symmetric 200 mM NaCl solutions buffered with phos phate. The channel was inactivated by depolarization, and this inactiv ation was reversed rapidly upon returning to -25 mV. The Cl- channel w as significantly permeant to Na+ ions (P-Na/P-Cl = 0.26), and the rela tive halide permeabilities were determined to be: I(1.92) > Br(1.73) > Cl(1.0) > F(0.34). The channel was inhibited by the common stilbene c ompounds (DIDS, SITS, DNDS), as well as by Zn2+ ions and an indanyloxy acetic acid derivative. A developmental role for the GCP Cl- channel i s suggested by the observation that adult rat brain synaptosomal membr anes were nearly devoid of this type of Cl- channel.