Effect of histamine and of the anaphylactic reaction on isolated guinea pig atria.

Addition of specific antigen to the isolated atria of sensitized guinea pigs and of histamine to those of nonsensitized animals resulted in an increase of both frequency and amplitude of contraction and in the appearance of rhythmic activity in the isolated left atrium. On a quantitative basis the anaphylactic response looks like the effects of histamine in concentrations between 10~ and 10~ mM/L. Xo qualitative differences between the effects of histamine and those of the anaphylactic reaction were observed. Since isolated atria thus are seen to participate in tissue sensitization, the heart should be considered as a potential shock organ in the anaphylactic reaction.