Distribution of 45Ca in the superior cervical ganglion of the cat

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Abstract
Superior cervical ganglia isolated from immature cats accumulated 0.9 ng atoms of 45Ca per mg wet weight during 10‐min incubations at 37°C; when expressed as an equivalent volume of medium the accumulation was four times the uptake of 3H‐inulin. Orthodromic stimulation of the ganglia doubled 45Ca accumulation, whereas excitation with 50 mM KCl, 5 mM glutamate, or antidromic stimulation increased accumulation by one‐half. Hexamethonium reduced the increment in 45Ca accumulation due to orthodromic stimulation only, but another ganglionic blocking agent, tetraethylammonium, did not reduce accumulation in any case. Both agents blocked ganglionic transmission monitored electrophysiologically. To resolve this discrepancy, and to approach the localization of 45Ca within the ganglia, the efflux of previously accumulated 45Ca was examined. The data could be fitted by an equation incorporating the sum of three exponentials, representing a rapidly exchanging compartment plus two more slowly exchanging ones. The latter two appeared to reflect the pre‐ and postganglionic elements in the ganglia: 45Ca content of the “preganglionic” compartment was increased by orthodromic but not by antidromic stimulation, and was not decreased by either blocking agent; conversely, 45Ca content of the “postganglionic” compartment was increased by both orthodromic and antidromic stimulation, and was decreased by both blocking agents after orthodromic stimulation. The lack of effect of tetraethylammonium on the whole ganglion resulted from an increase in “preganglionic” accumulation that offset the “postganglionic” decrease. After preganglionic denervation, the 45Ca content of the “preganglionic” compartment was reduced by two‐thirds, while the 45Ca content of the “postganglionic” compartment was unchanged. Chemical stimulation increased 45Ca accumulation in both compartments. Diphenylhydantoin, 0.1 mM, decreased the increment in 45Ca accumulation due to electrical stimulation and to 50 mM KCl; this inhibition occurred in the “preganglionic” compartment (and perhaps also in the “postganglionic”), and was accompanied by an increased efflux of 45Ca.