Poststimulation Increase of Synaptic Vesicle Number in the Preganglionic Nerve Terminals of the Cat Sympathetic Ganglion In Vivo

Abstract

Vesicular release of neurotransmitter has been suggested in a variety of nerve endings by morphological reports in which tetanic stimulation is shown to cause the reduction of synaptic vesicles (SVs) in number and simultaneously to depress the postsynaptic response (Ceccarelli et al., 1973; Heuser and Reese, 1973; Pysh and Wiley, 1974; Zimmerman and Whittaker, 1974a, b). Vesicular release of transmitter via exocytosis is supposed to be followed by the subsequent reformation of vesicles by endocytotic retrieval of terminal plasmamembrane by coated vesicles (recycling hypothesis of synaptic-vesicle membrane) (Heuser and Reese, 1973). Questions remains, however, concerning the vesicle hypothesis of the release of quanta of neurotransmitter (Zimmerman, 1979; Ceccarelli and Hurlbut, 1980; Tauc, 1979; Israel and Manarche, 1985). In addition, recent articles have shown the low rate of coated vesicles in the SV reformation, having implied the necessities of examinations for other mechanisms for supplying SVs during transmitter release (Kadota and Kadota, 1982; Meshul and Pappas, 1984; Parducz, 1986; Torri-Tarelli et al., 1987). The purpose of this study is to examine the ultrastructural changes in an neuro-neuronal synapse under normal supply of blood. The preganglionic nerve terminal of the cat superior cervical ganglion (SCG) was employed as the experimental material in the present experiment. It was simple to maintain this ganglion under intact blood sypply and to fix rapidly by perfusion via the lingual artery (Kadota and Kadota, 1982).