All
 D12 Amino Acids, Peptides, and Proteins D000602 +
 D12.776 Proteins D011506 +
 D12.776.543 Membrane Proteins D008565 +
 D12.776.543.750 Receptors, Cell Surface D011956 +
 D12.776.543.750.750 Receptors, Peptide D018000 +
 D12.776.543.750.750.555 Receptors, Neuropeptide D018013 +
 D12.776.543.750.750.555.610 Receptors, Opioid D011957 +
 D12.776.543.750.750.555.610.550 Receptors, Opioid, mu D017450 
 D12.776.543.750.750.555.610.200 Receptors, Opioid, delta D017465 
 D12.776.543.750.750.555.610.400 Receptors, Opioid, kappa D017473 
 D12.776.543.750.750.555.610.775 Receptors, sigma D017480