CALCIUM IONS NECESSARY TO SYNAPTIC TRANSMISSION IN PARASYMPATHETIC, NOT IN SYMPATHETIC, GANGLIA

¹ Department of Physiology, Stanford University, California

1. The parasympathetic paths to the sphincter pupillae of the cat are temporarily paralyzed by proper intravenous injections of sodium citrate—the paralysis probably being at synapses in the ganglia of the pathways just as has been demonstrated to be the case, in an earlier study, with respect to synapses in the cardiac ganglia of the parasympathetic pathways to heart muscle of the frog.

2. A sodium citrate injection which completely paralyzes synapses, for a few minutes, in the parasympathetic pathways mentioned above, does not paralyze sympathetic pathways to the constrictor musculature of the visceral blood vessels, to the chromaffin cells of the adrenal medulla, to the dilator pupillae, or to the retractor smooth muscle of the nictitating membrane, in the cat.

3. The parasympathetic and the sympathetic pathways studied differ from each other in that calcium ions are necessary for functioning at cholinergic synapses in the two parasympathetic ganglia but are not demonstrably necessary at cholinergic synapses in the four sympathetic ganglia studied.

4. Since other workers have shown the special importance of potassium ions at synapses of sympathetic ganglia, it is suggested that synapses in cholinergic ganglia may be of two classes, functionally—viz., calcium-cholinergic and potassium-cholinergic.