Enantiomeric Separation, Absolute Configuration by X-ray Crystallographic Analysis, and Functional Evaluation of Enantiomers of the Dual Ligand, SYA0340 at 5-HT1A and 5-HT7A Receptors.

We have previously identified 5-chloro-2-methyl-2-(3-(4-(pyridin-2-yl)piperazin-1-yl)propyl)-2,3-dihydro-1H-inden-1-one (SYA0340) as a dual 5-HT1A and 5-HT7 receptor ligand, and we posited such ligands might find utility in the treatment of various CNS related illnesses including cognitive and anxiolytic impairments. However, SYA0340 has a chiral center and its enantiomers may confound the readouts for their functional characteristics. Thus, in this study, we resynthesized SYA0340, separated the enantiomers, identified the absolute configurations, and evaluated their binding affinities and functional characteristics at both the 5-HT1A and 5-HT7A receptors. The results of this study show that the (+)-SYA0340-P1 [specific rotation [α] = +18.4 (deg.mL)/(g.dm)] has a binding affinity constant, Ki = 1.73 ± 0.55 nM at 5-HT1AR and Ki = 2.20 ± 0.33 nM at 5-HT7AR and (-)-SYA0340-P2 [specific rotation [α] = -18.2 (deg.mL)/(g.dm)] has Ki = 1.06 ± 0.32 nM (5-HT1AR) and 4.7 ± 1.1 nM (5-HT7AR). Using X-ray crystallographic techniques, the absolute configuration of the P2 isomer was identified as the S-enantiomer and, therefore, the P1 isomer as the R-enantiomer. Functionally, both SYA0340-P1 (EC50 = 1.12 ± 0.41 nM; Emax = 94.6 ± 3.1%) and SYA0340-P2 (EC50 = 2.21 ± 0.59 nM; Emax = 96.8 ± 5.1%) display similar agonist properties at the 5-HT1AR while both enantiomers display antagonist properties at the 5-HT7AR with P1 (IC50 = 32.1 ± 9.2 nM) displaying over 8 times greater potency as P2 (IC50 = 277 ± 46 nM). Thus, based on the functional evaluation results, SYA0340-P1 is considered as the eutomer of the pair of enantiomers of SYA0340. It is expected that these enantiomers will serve as new pharmacological probes for the 5-HT1A and 5-HT7A receptors.

New dual 5-HT1A and 5-HT7 receptor ligands derived from SYA16263.

We have previously reported that dual 5-HT1A and 5-HT7 receptor ligands might find utility as treatment options for various CNS related conditions including cognitive and anxiolytic impairments. We have also more recently reported that SYA16263 has antipsychotic-like properties with an absence of catalepsy in animal models ascribed to its ability to recruit ß-arrestin to the D2 receptor. However, SYA16263 also binds with very high affinity to 5-HT1AR (Ki = 1.1 nM) and a moderate affinity at 5-HT7R (Ki = 90 nM). Thus, it was of interest to exploit its pharmacophore elements in designing new dual receptor ligands. Using SYA16263 as the lead molecule, we have conducted a limited structure-affinity relationship (SAFIR) study by modifying various structural elements in the arylalkyl moiety, resulting in the identification of a new dual 5-HT1AR and 5-HT7R ligand, 6-chloro-2-methyl-2-(3-(4-(pyridin-2-yl)piperazin-1-yl)propyl)-2,3-dihydro-1H-inden-1-one (21), which unlike SYA16263, has a sub-nanomolar (5-HT1AR, Ki = 0.74 nM) and a low nanomolar (5-HT7R, Ki = 8.4 nM) affinity for these receptors. Interestingly, 21 is a full agonist at 5-HT1AR and antagonist at the 5-HT7R, functional characteristics which point to its potential as an antidepressant agent.

Taar1 gene variants have a causal role in methamphetamine intake and response and interact with Oprm1.

We identified a locus on mouse chromosome 10 that accounts for 60% of the genetic variance in methamphetamine intake in mice selectively bred for high versus low methamphetamine consumption. We nominated the trace amine-associated receptor 1 gene, Taar1, as the strongest candidate and identified regulation of the mu-opioid receptor 1 gene, Oprm1, as another contributor. This study exploited CRISPR-Cas9 to test the causal role of Taar1 in methamphetamine intake and a genetically-associated thermal response to methamphetamine. The methamphetamine-related traits were rescued, converting them to levels found in methamphetamine-avoiding animals. We used a family of recombinant inbred mouse strains for interval mapping and to examine independent and epistatic effects of Taar1 and Oprm1. Both methamphetamine intake and the thermal response mapped to Taar1 and the independent effect of Taar1 was dependent on genotype at Oprm1. Our findings encourage investigation of the contribution of Taar1 and Oprm1 variants to human methamphetamine addiction.

Commonalities and Distinctions Among Mechanisms of Addiction to Alcohol and Other Drugs.

BACKGROUND: Alcohol abuse is comorbid with abuse of many other drugs, some with similar pharmacology and others quite different. This leads to the hypothesis of an underlying, unitary dysfunctional neurobiological basis for substance abuse risk and consequences. METHODS: In this review, we discuss commonalities and distinctions of addiction to alcohol and other drugs. We focus on recent advances in preclinical studies using rodent models of drug self-administration. RESULTS: While there are specific behavioral and molecular manifestations common to alcohol, psychostimulant, opioid, and nicotine dependence, attempts to propose a unifying theory of the addictions inevitably face details where distinctions are found among classes of drugs. CONCLUSIONS: For alcohol, versus other drugs of abuse, we discuss and compare advances in: (i) neurocircuitry important for the different stages of drug dependence; (ii) transcriptomics and genetical genomics; and (iii) enduring effects, noting in particular the contributions of behavioral genetics and animal models.