to investigate the opioid receptor involved in mediating this response , morphine ( 3.5-105 nmol ) , [ d-ala2-d-leu5 ] enkephalin ( dadl , 1.05-35 nmol ) and u50 , 488h ( 35-1160 nmol ) , relatively selective ligands for the mu , delta and kappa receptors respectively , were injected intracerebroventricularly into conscious rats and the levels of catecholamines in plasma determined at the peak of the response .
C0034801
opioid receptor
C0064239
kappa receptors