Abstract: The present Work deals with a study on the authenticity and specificity of the antagonistic action of aminophylline upon the negative dromotropic effect of exogenous adenosine in guinea pig. Negative dromotropic agents (adenosine, acetylcholine, MnCl₂) and their antagonists (aminophylline, atropine) were injected into the auricle successively through two pre-inser-ted cannulae to expose their hidden interrelaions in terms of electrocardio-graphic manifestations. Experimental results disclosed that 0.06～0.18mL of 0.5mg/mL adenosine could invariably give rise to a second-degree A-V block, whereas 0.1～0.2mL of 30mg/mL aminophylline was capable of antagonizing completely the nega-tive dromotropic effeet induced by adenosine at the same dosage mentioned above in almost all the guinea pigs tested. The substitution of acetylcholine (5μg/mL ,0.03～0.20mL)or manganese chloride (10mg/mL, 0.3～1.5mL)for adenosine could achieve A-V block likewise, but the negative dromotropic effect of ACh andMnCl₂ was characterized by its inability to be antagonized by aminophylline. Atropine was noted for its evoking a blockade on the negative dromotropic effect of acetylcholine, but failed to exert any inf-luence upon the A-V block caused by adenosine. This study confirmed the authenticity of the autagonistic action of aminophylline on the negative dromotropic effect of adenosine, and moreover, testified the specificity of the antagonistic interaction between aminophylline and adenosine as compared with other A-V block-inducing agents like acetylcholine and MnCl₂.

Key words: adenosine, aminophylline, negative dromotropic effect, specific antagonistic action