SYNAPTOGENESIS AND CALCIUM CURRENT DISTRIBUTION IN CULTURED LEECH NEURONS

The distribution of calcium (Ca2+) currents was studied by loose-patch technique in Retzius cells isolated from the leech central nervous sy stem. Ca2+ tail currents were recorded in patches held at the equilibr ium potential for potassium (E(K)). Measurements were made from single cells and paired cells that had formed chemical or electrical synapse s in culture. In single Retzius cells, Ca2+ currents in the stump of t he initial process were three times larger than in the middle part of the soma; intermediate amplitudes were found in the polar region of th e soma. After the formation of chemical synapses, Ca2+ currents at the stumps of postsynaptic cells and in the polar region of the somas of presynaptic cells were reduced. The formation of electrical synapses d id not affect Ca2+ current distribution.