Antipsychotic properties of new N-(4-substituted-1-piperazinylethyl)- and N-(4-substituted-1-piperidinylethyl)-phthalimides

Design, synthesis, and evaluation of bitopic arylpiperazine-phthalimides as selective dopamine D3 receptor agonists

The dopamine D3 receptor (D3R) is a proven therapeutic target for the treatment of neurological and neuropsychiatric disorders. In particular, D3R-selective ligands that can eliminate side effects associated with dopamine D2 receptor (D2R) therapeutics have been validated. However, the high homology in signaling pathways and the sequence similarity between D2R and D3R have rendered the development of D3R-selective ligands challenging. Herein, we designed and synthesized a series of piperazine-phthalimide bitopic ligands based on a fragment-based and molecular docking inspired design. Compound 9i was identified as the most selective D3R ligand among these bitopic ligands. Its selectivity was improved compared to reference compounds 1 and 2 by 9- and 2-fold, respectively, and it was 21-fold more potent than compound 2. Molecular docking demonstrated that the orientation of Leu2.64 and Phe7.39 and the packing at the junction of helices may affect the specificity for D3R over D2R. Functional evaluation revealed that D3R-selective ligand 9i displayed a subpicomolar agonist activity at D3R with a 199-fold increase in potency compared to quinpirole. These results may be useful for the fragment-based design of bitopic compounds as selective D3R ligands.

Comparative studies of sulpiride and classical neuroleptics on induction of catalepsy, locomotor activity, and brain dopamine metabolism in mice

The effects of the peripheral administration of sulpiride on the induction of catalepsy, the vertical (VMA) and horizontal (HMA) locomotor activities, and on the dopamine metabolism in the limbic system, striatum, and nucleus accumbens were examined using mice up to 7.5 h after administration of drugs. These effects were compared to those of pimozide and haloperidol. Sulpiride (1.25-160 mg/kg, IP) clearly induced catalepsy similar to pimozide (0.0625-4 mg/kg, IP) and haloperidol (0.0375-0.3 mg/kg, IP). During the induction of catalepsy, the intensity was the strongest at 4.5 h after administration and the ED50 value showed 11.5 mg/kg at that time. However, a moderate dose of sulpiride at 10-20 mg/kg did not show the induction of a dose- and time-dependent catalepsy. During the locomotor activity, the VMA was significantly inhibited at 1.5 h and 6 h after administration of pimozide (0.25 mg/kg, IP) and haloperidol (0.075 mg/kg, IP) as compared to the control group, while the HMA was significantly inhibited at 1.5 h after administration of sulpiride (40 mg/kg, IP) and pimozide (0.25 mg/kg, IP). Subsequently, in the dopamine metabolism, sulpiride, pimozide, and haloperidol: 1) considerably accelerated the turnover in the dopamine metabolism in three distinct brain areas; 2) increased the levels of the DOPAC, HVA, and 3-MT even 6 h after administration, as well as at 1.5 h after administration; and 3) decreased the levels of dopamine in the nucleus accumbens at 1.5 h after administration. These results indicate that sulpiride displays a mode of action different from pimozide and haloperidol with regard to the induction of catalepsy, but not with regard to the locomotion and brain dopamine metabolism.

New hybrids of quipazine and trazodone as selective inhibitors of uptake of 5-hydroxytryptamine

Two new congeners, 4-(chloropropyl)-1-(2-quinolyl)piperazine- and 2-[3-[4-[2-(quinolyl)]-1-piperazinyl]propyl]-1,2,4-triazolo] 4,3-a]pyridin-3(2H)-one, of trazodone were synthesized and found to be potent and selective inhibitors of synaptosomal uptake of 5-hydroxytryptamine [5-HT, serotonin; IC50 = norepinephrine greater than 5 microM, 5-HT = 210-890 nM], with minimal effects in antagonizing (-)-apomorphine-induced climbing behavior and suppression of spontaneous locomotor activity in mice (ED50 greater than 50 mg/kg). The two compounds behaved like atypical antidepressants, since they weakly antagonized reserpine-induced hypothermia. The acute toxicity studies have shown that these compounds were less lethal when compared with imipramine or quipazine. Furthermore, chronic treatments (20 mg/kg, daily for 10 and 21 days) significantly decreased the isoprenaline-induced increase in cyclic AMP in the rat brain cortex, suggesting desensitization of beta-adrenoceptors. These findings point to the effects of these compounds as potential antidepressants dealing with specific serotonergic mechanisms.