Na⁺ regulates release of Ca⁺⁺ sequestered in synaptosomal mitochondria

The interactions of Na⁺ and Ca⁺⁺ were examined in synaptosomes and mitochondria. Na⁺ decreased both ⁴⁵Ca⁺⁺ binding to synaptosomes and loss of ⁴⁵Ca⁺⁺ from mitochondria. The ability of low concentrations of a local anesthetic, N,N-diethylamino-octyl 3,4,5-trimethoxybenzoate, to inhibit movement of Ca from intracellular bound stores was found to be associated with increased uptake of Ca by synaptosomes. A Na⁺-dependent regulatory effect was postulated between mitochondrial binding of Ca and influx of Ca into the nerve terminal. In addition, the results suggest difficulties in distinguishing between Na⁺-dependent and Ca⁺⁺-dependent processes in synaptosomal function.