Effect of dithiothreitol on histamine receptors in rabbit colon and guinea-pig ileum.

1. Dithiothreitol, an agent which reduces disulphide linkages to sulphydryl groups, potentiated the contractile responses of the rabbit colon and guinea-pig ileum to histamine, but had no effect on the resting tone or on the responses of these preparations to acetylcholine. 2. The potentiation was greater than that produced by antagonism of histamine's weak inhibitory action by metiamide, and still occurred after blockade of H2-receptors with metiamide; it is concluded that DTT potentiates responses to stimulation of H1-receptors in both preparations. 3. In this respect, these H1-receptors resemble those in vascular smooth muscle in the rabbit but not in the guinea-pig; it is concluded that there is a tissue variation rather than a species variation in the response of H1-receptors in the rabbit and guinea-pig to DTT.