Quinelorane is an octahydropyrimido[4,5-g]quinolone derivative patented by American pharmaceutical company Eli Lilly and Co. as for the treatment anxiety, Parkinson's syndrome, depression, and hypertension. Quinelorane acts as an agonist of dopamine agonist for the D2 and D3 receptors. In preclinical studies Quinelorane (IM) treatment produced dose-dependent effects on male sexual responding. Penile erections and masturbation were markedly facilitated following treatment with either 2.5 or 5 micrograms/kg quinelorane. Higher doses of quinelorane (10 and 25 micrograms/kg) generally did not further augment sexual responding but rather resulted in a return in sexual responding to control vehicle levels. Quinelorane had a biphasic effect on yawning behavior of the monkeys with low doses (2.5 and 5 micrograms/kg) facilitating yawning and high doses (25 micrograms/kg) inhibiting yawning.

Oxidopamine (6-Hydroxydopamine) is an antagonist of the neurotransmitter dopamine with potential antineoplastic activity. 6-Hydroxydopamine (6-HOD) can be taken up by selective adrenergic terminals, thereby causing acute degeneration of adrenergic terminals that leads to depletion of norepinephrine, and of dopamine in the dopamine-sensitive sites. This agent is auto-oxidated at physiological pH that leads to the formation of reactive free radicals, thereby leading to cytotoxicity in neural cells. 6-Hydroxydopamine is often used to induce CNS and sympathetic neural lesions that model aging and various nervous disorders in animal systems. The growth of C-1300 neuroblastoma was markedly slowed in 6-hydroxydopamine-treated mice. The growth of the A-10 breast adenocarcinoma was also significantly retarded in 6-hydroxydopamine-treated mice but the growth of B-16 melanoma was not affected.

Quinpirole (LY 171,555) is a psychoactive drug and research chemical which acts as a selective D2 and D3 receptor agonist. Quinpirole is the most widely used D2 agonist in in vivo and in vitro studies. Specific quinpirole binding in rat brain was saturable, and dependent on temperature, membrane concentration, sodium concentration and guanine nucleotides. Saturation analysis revealed high affinity binding characteristics (KD = 2.3 nM) which were confirmed by association-dissociation kinetics. The regional distribution of [3H]quinpirole binding sites roughly paralleled the distribution of [3H]spiperone binding sites, with greatest densities present in the striatum, nucleus accumbens and olfactory tubercles. A variety of drugs, most notably monoamine oxidase inhibitors (MAOls), inhibit the binding of [3H]quinpirole, but not [3H]spiperone or [3H](-)N-n-Propylnorapomorphine, in rat striatal membranes by a mechanism that does not appear to involve the enzymatic activity of MAO. Clinically antidepressant MAOIs exhibited selectivity between sites labeled by [3H]quinpirole and [3H]spiperone as did a number of structurally related propargylamines and N-acylethylenediamine derivatives and other drugs such as debrisoquin and phenylbiguanide. Quinpirole has been shown to increase locomotion and sniffing behavior in mice and induces compulsive behavior symptomatic of obsessive compulsive disorder in rats.

Bifeprunox, code name DU-127,090 is an atypical antipsychotic agent, which combines minimal D2 receptor agonism with 5-HT receptor agonism. Bifeprunox was in phase III of clinical trials for the treatment of schizophrenia, Bipolar Depression and in phase I for Parkinson's disease, but these studies were discontinued because efficacy data did not support pursuing the existing development strategy of stabilization of non-acute patients with schizophrenia.

Pardoprunox is a partial D2/3 dopamine receptor agonist and full 5-HT1A serotonin receptor agonist. Partial D(2/3) dopamine (DA) receptor agonists provide a novel approach to the treatment of the motor symptoms of Parkinson's disease that may avoid common dopaminergic side effects, including dyskinesia and psychosis. Pardoprunox passed phase III clinical trial for the treatment of Parkinson's disease.

Odapipam is a benzazepine with high affinity and selectivity for D1-dopamine receptors. Labeled with C-11, it has been used as a PET radiotracer to visualize D1 receptors both in striatal and extrastriatal areas, such as the prefrontal cortex. Odapipam inhibits dopamine D1 receptor binding in vitro with low nanomolar to picomolar dissociation constants. The affinity of [11C]NNC 756 for D1 receptors is 0.18 nM. Odapipam was tested in phase I of clinical trials for the treatment of psychotic disorders, but failed.

Nolomirole (CHF1035) is an orally active, selective dopamine agonist, primarily activating DA2- and alpha2 receptors, thereby inhibiting norepinephrine release, which may be beneficial in heart failure. Nolomirole is able to attenuate the heart failure signs in the monocrotaline-induced congestive heart failure. CHF1035 is a mixture of two enantiomers, CHF1800 (+) and CHF1810 (-). CHF1035 and its metabolite CHF1024 significantly decreased the IOP in rabbits, and are potential novel IOP lowering agents. Especially, CHF1035 produced a substantial decrease in IOP for a prolonged period of time, and thus may prove useful in glaucoma therapy. Nolomirole is a pre-synaptic stimulator of DA2-dopaminergic and α2-adrenergic receptors in peripheral sympathetic nerve endings. These receptors act as a negative feedback mechanism, inhibiting norepinephrine secretion. In early phase clinical studies lasting 1–3 months, nolomirole reduced peripheral systemic resistance and 24 hour blood pressure and increased cardiac output. In a study of 29 patients with heart failure, followed for 10 days, a reduction in plasma norepinephrine was demonstrated. In spite of the fact that Nolomirole was in clinical trials for the treatment of heart failure, its development was discontinued.

Lirexapride serotonin 5-HT4 receptor and dopamine D2 receptor agonists. It had been in phase II clinical trials for the treatment of irritable bowel syndrome. However, this research has been discontinued.

Berupipam (also known as NNC 22-0010), a dopamine antagonist with a high affinity and selectivity for D1 receptor has been studied for patients with psychotic disorders. Berupipam participated in phase I clinical trials; however, further development of this drug was discontinued

Adoprazine (SVL-313) is a full 5-HT1A receptor agonist and full D2/3 receptor antagonist possessing characteristics of an atypical antipsychotic, representing a potential novel treatment for schizophrenia and bipolar disorder. This drug together with some others, e.g. Mazapertine succinate, PF-217830 was discontinued from clinical trials due to either non-optimal pharmacokinetic properties or insufficient therapeutical efficacy.