the putative regulatory effect of opioids on adenylate cyclase was investigated in two different preparations containing , respectively , two different populations of opioid receptors : the rabbit cerebellum ( greater than 75 % mu-opioid receptors ) and the guinea pig cerebellum ( greater than 80 % kappa-opioid receptors ) .
C0034801
opioid receptors
C0064239
kappa-opioid receptors