Pharmacological Receptors in the Rat Stomach Fundus

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Abstract
The heating procedure of Fleisch and Ehrenpreis is a poorly selective but useful tool for approaching the chemical nature of the pharmacolog ical receptors. According to their stability to a 47°C temperature, for 20 min, receptors may be considered as heat-labile (protein-receptors?) and heat-stable receptors (protein-stable or nonprotein receptors). Both dexamphetamine- and 5-hydroxytryptamine-induced contractions of isolated rat stomach fundal strips werefound to be inhibited by heating. The finding that both amines act on heat-labile receptors should provide a further support for the hypothesis of a common receptor. The mild temperature employed causes some extensive tissue damage, in addition to the denaturation of the heat-labile receptors for dexamphetamine, 5-HT and BaCl2. It alters slightly the cell membrane, as shown by a transient inhibition of the electrically-induced contraction, by inconstantly occurring modifications of the electrical activity, and more, by the net and slowly reversible blockade of the KCl-provoked contraction. The strong inhibition of the BaCl2-induced contraction suggests that barium ions bind with heat-labile membrane structures. Finally, the cholinergic drug furtrethonium acts on heat-stable receptors.

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