Modification by Temperature of Conduction and Ganglionic Transmission in the Gastropod Nervous System

The pedal ganglia of the terrestrial gastropod Ariolimax contain junctions between nerve fibers which are shown to be preferential points of fatigue and which exhibit facilitation (summation) of preganglionic impulses to produce a postganglionic spike. These characteristics in conjunction with others previously reported (reversible susceptibility to nicotine, convergence of preganglionic impulses, and inhibition of transmission through setting up a refractory state in the postganglionic fiber) are considered sufficient to indicate synaptic transmission in the pedal ganglia. The mean conduction velocity of the fastest fibers in the pedal nerves is 0.52 meter per second for preganglionic and 0.50 meter per second for postganglionic fibers at 7.56 degrees C. The conduction rates at 21.76 degrees C. are respectively 0.80 meter per second and 0.83 meter per second. The mean ganglionic delay is 0.033 second at 7.56 degrees C. and 0.019 second at 21.76 degrees C. The mean Q(10)'s for conduction velocity are thus 1.37 for preganglionic and 1.42 for postganglionic fibers. The mean Q(10) for ganglionic delay is 1.49. If the assumption is made that the Q(10) for ganglionic delay is that of a limiting reaction, this figure then represents a value below which the Q(10) for synaptic delay is statistically improbable.