Developmental differences in dopamine synthesis inhibition by (±)-7-OH-DPAT
The proposed D3-selective ligand (+/-)-7-hydroxy-N,N-dipropylaminotetralin (7-OH-DPAT) inhibited tyrosine hydroxylase in vitro (IC50 = 0.6-0.7 microM) and dihydroxyphenylalanine (DOPA) accumulation in vivo (ID50 = 4.8-6.4 mg/kg) in two autoreceptor models in extrapyramidal and limbic tissue in rat forebrain, without consistent regional selectivity. Some limbic selectivity (ID50 = 10 vs. 29 mg/kg) was found in an in vivo model permitting expression of postsynaptic D3 and D2 receptor activity. The effects were partially blocked by S(-)-eticlopride alone, and fully after reserpine pretreatment. The results suggest that 7-OH-DPAT activates D3 or D2 autoreceptors, alters dopamine storage or release, and may interact with some limbic selectivity at postsynaptic D3 and D2 receptors as a partial agonist.