Combined dopamine D 2 receptor antagonism and serotonin (5-HT) 1A receptor agonism may improve efficacy and alleviate some side effects associated with classical antipsychotics. The present study describes the in vitro and in vivo characterization of 1-(2,3-dihydrobenzo[1,4]dioxin-5-yl)-4-[5-(4-fluoro-phenyl)-pyridin-3-ylmethyl]-piperazine monohydrochloride (SLV313), a D 2/3 antagonist and 5-HT 1A agonist. SLV313 possessed high affinity at human recombinant D 2 , D 3 , D 4 , 5-HT 2B , and 5-HT 1A receptors, moderate affinity at 5-HT 7 and weak affinity at 5-HT 2A receptors, with little-no affinity at 5-HT 4 , 5-HT 6 , a 1 , and a 2 (rat), H 1 (guinea pig), M 1 , M 4 , 5-HT 3 receptors, and the 5-HT transporter. SLV313 had full agonist activity at cloned h5-HT 1A receptors (pEC 50 ¼ 9.0) and full antagonist activity at hD 2 (pA 2 ¼ 9.3) and hD 3 (pA 2 ¼ 8.9) receptors. In vivo, SLV313 antagonized apomorphine-induced climbing and induced 5-HT 1A syndrome behaviors and hypothermia, the latter behaviors being antagonized by the 5-HT 1A antagonist WAY100635. In a drug discrimination procedure SLV313 induced full generalization to the training drug flesinoxan and was also antagonized by WAY100635. In the nucleus accumbens SLV313 reduced extracellular 5-HT and increased dopamine levels in the same dose range. Acetylcholine and dopamine were elevated in the hippocampus and mPFCx, the latter antagonized by WAY100635, suggesting possible 5-HT 1A -dependent efficacy for the treatment of cognitive and attentional processes. SLV313 did not possess cataleptogenic potential (up to 60 mg/kg p.o.). The number of spontaneously active dopamine cells in the ventral tegmental area was reduced by SLV313 and clozapine, while no such changes were seen in the substantia nigra zona compacta following chronic administration. These results suggest that SLV313 is a full 5-HT 1A receptor agonist and full D 2/3 receptor antagonist possessing characteristics of an atypical antipsychotic, representing a potential novel treatment for schizophrenia. Neuropsychopharmacology (2007) 32, 78-94.

Background: Neuropeptidases metabolize regulatory peptides and hormones. Results: A new type of neuropeptidase inhibitor binds away from the catalytic site, is noncompetitive with short peptide substrates, and promotes the open enzyme conformation. Conclusion:The inhibitor restricts a conformational change associated with substrate cleavage. Significance: Inhibitors of this class will allow more specific modulation of neuropeptidases, aiding therapeutic development.

Present Parkinson's disease treatment strategies are far from ideal for a variety of reasons; it has therefore been suggested that partial dopamine receptor agonism might be a potential therapeutic approach with potentially fewer side effects. In the present study, we describe the in vitro characterization of the nonergot ligand SLV308 (7-[4-methyl-1-piperazinyl]-2(3H)-benzoxazolonemonohydrochloride). SLV308 binds to dopamine D(2), D(3), and D(4) receptors and 5-HT(1) (A) receptors and is a partial agonist at dopamine D(2) and D(3) receptors and a full agonist at serotonin 5-HT(1) (A) receptors. At cloned human dopamine D(2,L) receptors, SLV308 acted as a potent but partial D(2) receptor agonist (pEC(50) = 8.0 and pA(2) = 8.4) with an efficacy of 50% on forskolin stimulated cAMP accumulation. At human recombinant dopamine D(3) receptors, SLV308 acted as a partial agonist in the induction of [(35)S]GTPgammaS binding (intrinsic activity of 67%; pEC(50) = 9.2) and antagonized the dopamine induction of [(35)S]GTPgammaS binding (pA(2) = 9.0). SLV308 acted as a full 5-HT(1) (A) receptor agonist on forskolin induced cAMP accumulation at cloned human 5-HT(1) (A) receptors but with low potency (pEC(50) = 6.3). In rat striatal slices SLV308 concentration-dependently attenuated forskolin stimulated accumulation of cAMP, as expected for a dopamine D(2) and D(3) receptor agonist. SLV308 antagonized the inhibitory effect of quinpirole on K(+)-stimulated [(3)H]-dopamine release from rat striatal slices (pA(2) = 8.5). In the same paradigm, SLV308 had antagonist properties in the presence of quinpirole (pA(2) = 8.5), but the partial D(2) agonist terguride had much stronger antagonistic properties. In conclusion, SLV308 combines high potency partial agonism at dopamine D(2) and D(3) receptors with full efficacy low potency serotonin 5-HT(1) (A) receptor agonism and is worthy of profiling in in vivo models of Parkinson's disease.

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