[The synaptology of 2 types of neurons in the sympathetic ganglia of the frog].
This work is based on the selective section of the B or C preganglionic fibres innervating respectively the B or C neurons of the last two abdominal ganglia of the sympathetic chain in the frog. A quantitative study of three morphological features of their synapses was performed for each of the two neuronal types. Significant differences were observed in the mean size of the preganglionic ending sections; on the contrary there were no differences in the mean length of the active zones. The subsynaptic apparatus, which is fairly frequent in this material, is not restricted to one neuronal type, although much more frequent in the synapses of B neurons. The modifications of the innervation of ganglionic neurons after selective section of one type of preganglionic fibres were followed measuring the synaptic density, using a synaptic index and an index of simple contacts. It appeared that, after selective degeneration of preganglionic C fibres, their regeneration being prevented, the preganglionic B fibres were able to from functional synapses on C neurons with a short latency, normal values of synaptic density being reached within 2 months. On the contrary, after degeneration of the preganglionic B fibres, the preganglionic C fibres reinnervated B neurons with a limited efficiency, in such a way that the synaptic density remained after several months much lower than normal and that electrophysiological recordings of synaptic transmission were limited to 44% of the impaled neurons. Possible interpretations of these data are discussed.
Taxi
J
J
Institut des Neurosciences, Université Pierre et Marie Curie, Paris, France.
Eugene
D
D
D000818:Animals; D005728:Ganglia, Sympathetic / Q000648:ultrastructure*; D009412:Nerve Fibers / Q000648:ultrastructure; D009474:Neurons / Q000145:classification / Q000648:ultrastructure*; D011898:Ranidae; D013569:Synapses / Q000145:classification / Q000648:ultrastructure*
Sinaptologiia dvukh tipov neĭronov simpaticheskikh gangliev liagushki.