Journal of Neuroscience, Vol 1, 1180-1192, Copyright © 1981 by Society for Neuroscience
Membrane potential of olfactory bulb synaptosomal fractions: characterization with the lipophilic cation tetraphenylphosphonium
S Rochel, D Lichtstein, AJ Blume and FL Margolis
The membrane potential of olfactory bulb synaptosomal fractions was
monitored with the lipophilic cation tetraphenylphosphonium (TPP+), which
has been reported to distribute across membranes according to the Nernst
equation. The properties of the synaptosomal membrane potential as
monitored with TPP+ were similar to those reported for neural tissues using
other measurement techniques. There is an electrical potential (delta psi)
of -64 and -77 mV in the P1 and P2 synaptosomal fractions, respectively.
This potential is due primarily to the K+ diffusion gradient across the
synaptosomal membrane. The influence of ouabain on TPP+ accumulation
indicates that the (Na+,K+)-ATPase electrogenicity contributes about -20 mV
to the resting synaptosomal membrane potential. Veratridine induced a
decline in TPP+ accumulation which was blocked by tetrodotoxin or by the
omission of Na+ from the medium. A significant mitochondrial contribution
to TPP+ accumulation, which varied as a complex function of TPP+
concentration in the medium in a manner indicating that TPP+ interfered
with the maintenance of mitochondrial potential, was observed. This
mitochondrial contribution could be eliminated by performing the
experiments anaerobically in the presence of oligomycin. The results are
discussed with relation to the future possible use of TPP+ for delta psi
measurements in synaptosomal preparations.