Evidence from desensitization studies for distinct receptors for ATP and UTP on the rat superior cervical ganglion.

Prolonged contact of the rat superior cervical ganglia (SCG) with the purine alpha,beta-methylene-ATP (alpha,beta-Me-ATP) selectively depressed responses to ATP and alpha,beta-Me-ATP but not responses to uridine 5'-triphosphate (UTP), potassium or adenosine. Prolonged contact with the pyrimidine UTP selectively depressed responses to UTP but not responses evoked by alpha,beta-Me-ATP, potassium or adenosine. These results are consistent with the presence of P2-purinoceptors and pyrimidinoceptors on the rat SCG and the hypothesis that pyrimidinoceptors exist within the nervous system.