Calcium binding sites of hamster parasympathetic neurons

Sites of Ca localization in hamster submandibular ganglion cells have been studied by electron microscopy using the technique of Oschman et al. [11]. Electron-dense deposits, which we assume to contain Ca, are found: (i) on axonal plasma membranes; (ii) on the plasma membranes of neuron soma and its processes; (iii) on the membrane of clear vesicles in the nerve terminal; and (iv) in the matrix of mitochondria. Intracellularly injected Ca accumulates in the mitochondria. Caffeine reduces the electron-dense deposits seen in mitochondria. Caffeine induces a swelling of Golgi apparatus when applied with CaCl2, but this swelling is not observed without CaCl2. These results are discussed in the light of Ca-activated K-conductance increases, which induce 4 types of membrane potential changes [18, 19].