Post-tetanic potentiation in ganglia which are blocked with hexamethonium

1 Post-tetanic potentiation (p.t.p.) of the compound action potential in the presence of hexamethonium was observed in the isolated stellate ganglion of the hamster using extracellular postganglionic recordings. 2 The magnitude of the p.t.p. was small (less than a 20% increase) in the control solution, but increased as the depth of blockade with hexamethonium was increased. 3 The magnitude of the p.t.p. was frequency-dependent between 1 and 40 Hz. 4 Atropine partially blocked the p.t.p. 5 McN-A-343, a muscarinic agonist, potentiated ganglionic transmission which had been partially blocked by hexamethonium. 6 Repetitive stimulation in the presence of hexamethonium potentiated the discharges induced by DMPP, a nicotonic agonist. The potentiation was blocked by atropine. 7 It was concluded that the p.t.p. in the presence of hexamethonium has the same characteristics as p.t.p. in the control solution. There appears to be both a muscarinic component and a presynaptic component of the p.t.p.