Effects of adenosine and its analogues on isolated internal carotid arteries from newborn and adult pigs.

Vasorelaxant effects of adenosine and its analogues, 5'-N-(ethylcarboxamide) adenosine (NECA), N6-(l-phenylisopropyl)-adenosine (l-PIA) and N6-cyclohexyladenosine (CHA), on isolated internal carotid arteries from newborn (1-3 days) and adult (6 months) pigs were compared. The order of vasorelaxant potencies of adenosines was: NECA greater than l-PIA greater than adenosine greater than CHA for the adult arteries and NECA greater than l-PIA greater than adenosine = CHA for the newborn arteries. Sensitivities of vessels from the newborn and mature animals to CHA and l-PIA did not differ. However, carotid arteries from the newborn pigs were less sensitive to NECA and adenosine than the adult arteries (p less than 0.05). Theophylline caused an approximately 3-fold shift to the right of the relaxant concentration-response curves to all the four adenosines on arteries from pigs of both age groups. These data suggest that adenosine is not as effective a vasodilator in the newborn as it is in the adult.