Electrically-evoked release of [3H]-histamine from the guinea-pig hypothalamus.

1 [3H]-histamine was taken up by slices of guinea-pig hypothalamus against a concentration gradient. 2 Electrical field stimulation of the superfused slices resulted in an increased efflux of radioactivity, the major part of which was shown to be associated with histamine by paper chromatography. 3 The evoked release of histamine was dependent on calcium ions in the superfusate and was increased by 56% when the frequency of stimulation was doubled from 5 to 10 Hz.