The effects of adrenaline on the isolated frog's heart at 27 degrees C are not antagonized by phentolamine (1.5 x 10(-6)M) but are abolished at 7 degrees C.2. At 27 degrees C isoprenaline was more potent than noradrenaline, but at 7 degrees C noradrenaline was more potent than isoprenaline.3. Phenoxybenzamine (1.5 x 10(-5)M) or dibenamine (1.5 x 10(-5)M) at 7 degrees C abolished the work output induced by adrenaline. When the temperature was raised to 24 degrees C, adrenaline caused an increase in work output.4. It is concluded that in the isolated frog heart there are at least two pools of adrenoceptors, the availability of which can be governed by temperature.
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Buckley et al. (1970) studied this question.
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