Synaptogenesis and calcium current distribution in cultured leech neurons

Abstract

The distribution of calcium (Ca$^{+}$) currents was studied by loose-patch technique in Retzius cells isolated from the leech central nervous system. Ca$^{+}$ tail currents were recorded in patches held at the equilibrium potential for potassium (E$_{\text{K}}$). Measurements were made from single cells and paired cells that had formed chemical or electrical synapses in culture. In single Retzius cells, Ca$^{+}$ currents in the stump of the initial process were three times larger than in the middle part of the soma; intermediate amplitudes were found in the polar region of the soma. After the formation of chemical synapses, Ca$^{+}$ 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 did not affect Ca$^{+}$ current distribution.