| Effect of tetanus toxin on the accumulation of the permeant lipophilic cation tetraphenylphosphonium by guinea pig brain synaptosomes | |||||||||||
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| Accumulation of the permeant lipophilic cation [3H]tetraphenylphosphonium (TPP+) by synaptosome preparations from guinea pig brain cerebral cortex is inhibited 1:10 by medium containing 193 mM K+ and by veratridine. A further 1:10 to 1:15 decrease in TPP+ uptake occurs under nitrogen and in the presence of mitochondrial inhibitors such as oligomycin, whereas starvation and succinate supplementation have no effect. These data indicate that, in analogy to intact neurons, there is an electrical potential (ΔΨ, interior negative) of -60 to -80 mV across the synaptosomal membrane that is due primarily to a K+ diffusion gradient (K+in→K+out). The data also indicate that mitochondria entrapped within the synaptosome but not free mitochondria make a large contribution to the TPP+ concentration gradients observed. | |||||||||||
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