QUANTAL SECRETION RECORDED FROM VISUALIZED BOUTONS

A method is described for recording the electrical signs of transmissi on at single boutons. Monopolar rat pelvic ganglion cells are electric ally compact and receive an innervation from either single hypogastric or pelvic nerves that consists of a set of boutons which innervate th e soma of the cells; each bouton possesses an active zone and can be o bserved with the confocal microscope after dextran-rhodamine orthograd e labelling of the hypogastric nerves. Extracellular electrodes of abo ut 8 mu m diameter can be positioned in the loose-patch configuration over visualized boutons following their fluorescence with the vital dy e, 3,3-diethyloxardicarbocyanine iodide (DiOC(2)(5)). Excitatory post- synaptic currents (EPSCs), due to stimulation of the hypogastric nerve , can be recorded from boutons in this way, provided that [Ca2+](0) is lowered sufficiently to ensure failure of the initiation of the soma action potential by the EPSCs.