Effects of physostigmine on the afterdischarge and slow postsynaptic potentials of bullfrog sympathetic ganglia.

1. The effects of anticholinesterases (anti-ChEs) (physostigmine, prostigmine and TEPP) on the afterdischarges and the extracellular and intracellular slow potentials of bullfrog sympathetic ganglia were studied.2. The anti-ChEs augmented the early afterdischarge, the late negative potential and the slow excitatory postsynaptic potential. This indicated that the nature of the early afterdischarge was cholinergic (muscarinic) and that the late negative potential or the slow excitatory postsynaptic potential generated the early afterdischarge.3. Since the anti-ChEs increased the positive potential, the depression of the early afterdischarge observed in the presence of an antiChE was explained to be caused by the increased inhibitory effect of the enhanced positive potential.4. Prostigmine and tetraethyl pyrophosphate did not show any appreciable effects on the late afterdischarge, the late late negative potential nor the late slow excitatory postsynaptic potential. This indicated that the nature of the late afterdischarge was non-cholinergic and that the late late negative potential or the late slow excitatory postsynaptic potential generated the late afterdischarge.5. Physostigmine reversibly depressed the late afterdischarge, the late late negative potential and the late slow excitatory postsynaptic potential. The depressant action of physostigmine was not due to its anti-ChE action.