EVIDENCE FOR 2 ADENINE DERIVATIVE RECEPTORS IN RAT ILEUM WHICH ARE NOT INVOLVED IN THE NONADRENERGIC, NONCHOLINERGIC RESPONSE

The receptors mediating inhibition of the rat ileum by adenosine and adenine nucleotides were studied. ATP and ADP were more potent than AMP or adenosine. Theophylline antagonized the effects of adenosine and AMP but not those of ATP or ADP. Preparations desensitized to ATP or ADP were still inhibited by adenosine and vice versa. The nonadrenergic, noncholinergic inhibition produced by field stimulation or nicotine was not attenuated by the presence of theophylline or desensitization to ATP. These data indicate that more than one adenine derivative receptor is present in rat ileum and that ATP and adenosine are unlikely candidates for the unknown transmitter.