The intrinsic "spontaneous" activity of a nerve center can vary in number of active units and in unit frequencies. An analysis of a synchronous nerve center, the Limulus heart ganglion, has recently been made (Prosser, '43). A partial analysis of an asynchronous center, the abdominal ganglia of the crayfish, was made by Prosser ( '40 a). It was found that the activity of the crayfish ganglia increased when potassium in the bathing saline was low and activity diminished when potassium was high, there was little effect of calcium, and most of the changes in activity were due to changes in the number of units active. Prosser ( '40 b) also noted that under conditions of increased intrinsic activity synaptic summation was enhanced and in lowered intrinsic activity synaptic transmission was depressed.
Roeder ('41) repeated the experiments of Prosser ('Ma) and his results disagreed. He found that both high and low potassium decreased intrinsic activity ; the gross frequency was greatest when the potassium concentration was slightly higher than in the standard saline. Roeder also observed calcium antagonism of the potassium effects.
The present paper is (1) an explanation of the difference between the results of Roeder and Prosser, (2) an analysis of the effects of potassium and calcium upon single units in the crayfish ganglia, and (3) an .examination of the effects of monovalent cations and of anions upon the intrinsic activity in crayfish ganglia.
PROCEDURE
There are four principal differences between the procedures of Roeder and Prosser :
- Roeder used an impulse integrator which added and counted in nearly continuous record all the impulses above a given magnitude, while Prosser recorded intermittently by photographing an oscillograph. The two methods of recording should and probably do yield similar results with respect to gross frequency, but. the integrator gives no evidence regarding the behavior of single units.