CGP 25454A is a novel and selective presynaptic dopamine autoreceptor antagonist.In vitro: CGP 25454A increase the field-stimulated [3H]- and [14C]-overflow from rat striatal slices preloaded with [3H]dopamine and [14C]choline, indicating that CGP 25454A is able to enhance the release of both dopamine (DA) and acetylcholine (ACh). However, CGP 25454A is 12.9 times more potent in increasing, by 1/6 of the apparent maximal increase, the release of [3H]DA than that of [14C]ACh.In vivo: CGP 25454A increase [3H]spiperone binding to receptors of the D2 family in rat striatum by 90-110% (ED50: 13 mg/kg i.p.). As a similar increase in [3H]spiperone binding is found with a variety of agents which increase the synaptic concentration of endogenous DA, the effect of CGP 25454A most probably reflects an enhanced release of DA under in vivo conditions. At 30-100 mg/kg, CGP 25454A inhibit [3H]spiperone binding in the pituitary of the same animals as a result of a blockade of postsynaptic DA receptors. Form:Solid