IT HAS recently been shown that nerve cell activity, induced in an excised sympathetic ganglion by stimulation of its preganglionic nerve, increases the rate of labelling of phosphatidyl inositol by 32P from inorganic phosphate (LARRABEE, KLINGMAN and LEICHT, 1963). The increase in rate of labelling can be as great as two-fold. No increase in labelling was observed in any of the other phospholipids examined, which included phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidic acid, although other investigators have reported that labelling of phosphatidic acid can be increased by stimulating sympathetic ganglia with acetylcholine plus eserine (HOKIN, HOKIN and SHELP, 1960).The purpose of the present experiments was to investigate the locus of the effect of neuronal activity on labelling of phosphatidyl inositol. Was it presynaptic or postsynaptic? Did it occur in dendrites, cell bodies, or axons? Was it related to impulse conduction or to synaptic transmission ?The investigation included a comparison of various ganglia and nerve trunks, the effects of block of ganglionic transmission with tubocurarine, the effects of impulses conducted antidromically into a sympathetic ganglion, and chemical as well as electrical stimulation.
M E T H O D SThe majority of the experiments were made on tissues excised from adult white rats, usually females weighing 180-220 g, anaesthetized with urethane. The tissues included superior cervical ganglia in continuity with lengths of preganglionic and postganglionic nerves, cervical sympathetic (preganglionic) nerve trunks, vagus nerve trunks, the non-synaptic (sensory) ganglion nodosum of the vagus nerve, and phrenic nerves. For comparison, a few superior cervical ganglia from mice, hamsters, and rabbits were studied. Before incubation, connective tissue sheaths were removed from the sympathetic ganglia of rats and rabbits, from the preganglionic nerves, and from the vagal ganglia. The sheaths were not removed from phrenic nerves or from the mouse or hamster ganglia.Typical wet weights of the preparations (in /cg) were as follows. Sympathetic ganglia: rat, 820; mouse, 130; hamster, 450; rabbit, 4200. Vagus ganglia from rat, 500. Rat nerve trunks: cervical sympathetic, 70; vagus, 750; phrenic, 940. Ratios of wet weight to dry weight for superior cervical ganglia of rats, determined occasionally during the course of these experiments, averaged 5.2 i 0.1 (mean f s.E.M., N = 9).The tissues were incubated at 37", typically for 4 hrs, in a bicarbonate-buffered physiological solution containing glucose. To this was added inorganic [32P]phosphate, usually about 20 pc/ml, and about 10 /cc/ml of glucose, uniformally labelled with 14C (specific activity at least 60 mc/m-mole). Carrier-free [32P]phosphate was obtained from E. R. Squibb and Sons, and labelled glucose from Nuclear Chicago Corp. or New England Nuclear Corp. The solution was kept in motion around the preparation by continual bubbling of 5 % C02-95 % 02.
