Antidromic inhibition of acetylcholine release from presynaptic nerve terminals in bullfrog's sympathetic ganglia.

In isolated bullfrog's sympathetic ganglia it was examined if the release of acetylcholine (ACh) from presynaptic nerve terminals was changed when postsynaptic ganglion cells were activated antidromically. The fast excitatory postsynaptic potential (fast EPSP) of ganglion cells was found to be depressed, whereas the nicotinic ACh potential of these cells was not depressed, immediately after these ganglion cells were activated by antidromic axonal or direct intracellular stimulations. This indicates that activation of ganglion cells results in inhibiton of the release of ACh from their presynaptic nerve terminals. Such an antidromic inhibition of ACh release could not be clearly observed when preparations were perfused with Ca2+-deficient solution or when adrenaline (10(-5) M) was added to the superfusion solution. Frequency of the spontaneous miniature EPSP was also found to be decreased after antidromic activation of ganglion cells. On the basis of these results it was concluded that some kind of transmitter was released from activated ganglion cells which inhibited ACh release by acting on preganglionic nerve terminals. This putative neurotransmitter was suggested to be adrenaline.