Effect of splanchnic nerve stimulation on epinephrine and norepinephrine release from gastrointestinal sympathetic postganglionic endings in the frog.

Gastrointestinal vascular perfusates in bullfrogs before and after splanchnic nerve stimulation were collected and analyzed for epinephrine and norepinephrine. Catecholamine in the perfusate before stimulation was predominantly epinephrine. Upon stimulation a marked increase in epinephrine release without any significant change in norepinephrine release was observed in experiments at 8-10 degrees C as well as 16-21 degrees C, showing that in frogs epinephrine is the sympathetic neurotransmitter and that the release of epinephrine is not affected by low temperatures.