A series of analogues of the potent and selective n receptor ligand 1, 3-ditolylguanidine (DTG) were synthesized and demonstrated to have high affinity for the u receptor as measured by in-vitro [3H] DTG displacement studies using guinea pig brain tissue. Three of these l-aryl-3-(l-adamantyl) guanid~ es were radiolabeled-two with carbon-11 and one with fluorine-18. Radiochemical yields and specific activities were sufficient for these ...
