effects of the adenosine analogs r-n6-phenylisopropyl-adenosine ( r-pia ) and 5'-n-ethylcarboxamidoadenosine ( neca ) , alone and in combination with caffeine , were studied in squirrel monkeys trained to respond under multiple fixed-interval fixed-ratio schedules of reinforcement .
C0001443
adenosine
C0050789
5