New perspectives for the treatment of disorders of sleep and arousal

Synthesis and evaluation of aporphine analogs containing C1 allyl isosteres at the h5-HT(2A) receptor

A series of C1 aporphine analogs related to compound 5 and that contain substituted allylic, alkynyl, nitrile, ester and benzyl groups was synthesized and evaluated for affinity at h5HT2A and α1A receptors in functional activity assays that measure calcium release. The presence of branched allylic substituent groups diminished affinity for the h5HT2A receptor. Likewise, the alkynyl, nitrile and ester derivatives evaluated displayed lower 5-HT2A receptor affinity as compared to 5. Hydrophobic, steric and electronic effects impact the affinity of p-substituted benzyl derivatives 8i-8k but in different ways. High hydrophobicity and size favor 5-HT2A affinity whereas, high electronegativity disfavors 5-HT2A affinity. p-Bromobenzyl analog 8k was identified as a 5-HT2A receptor selective ligand, with the highest 5-HT2A receptor affinity of any aporphine known to date. Most of the other analogs were selective for the 5-HT2A versus the α1A receptor. ChemScore binding energies from docking studies correlated qualitatively with the observed trends in affinity for 8i-8k, although the binding energies were not well differentiated quantitatively.

The role of melatonin in patients with chronic kidney disease undergoing haemodialysis

Patients with chronic kidney disease including those undergoing haemodialysis have deranged sleep-wake pattern. In large part this is due to an abnormal circadian cycle of melatonin, a hormone secreted by the pineal gland in the evening and induces sleep. Subjects undergoing automated peritoneal dialysis or nocturnal haemodialysis have better sleep profile compared to those on daytime dialysis. Studies have shown that exogenous melatonin improves sleep-wake cycle in daytime haemodialysis patients. However, large randomised controlled trials are needed in order to establish its role in this patient population.

Affinity of aporphines for the human 5-HT2A receptor: insights from homology modeling and molecular docking studies

Analogs of nantenine were docked into a modeled structure of the human 5-HT(2A) receptor using ICM Pro, GLIDE, and GOLD docking methods. The resultant docking scores were used to correlate with observed in vitro apparent affinity (K(e)) data. The GOLD docking algorithm when used with a homology model of 5-HT(2A), based on a bovine rhodopsin template and built by the program MODELLER, gives results which are most in agreement with the in vitro results. Further analysis of the docking poses among members of a C1 alkyl series of nantenine analogs, indicate that they bind to the receptor in a similar orientation, but differently than nantenine. Besides an important interaction between the protonated nitrogen of the C1 alkyl analogs and residue Asp155, we identified Ser242, Phe234, and Gly238 as key residues responsible for the affinity of these compounds for the 5-HT(2A) receptor. Specifically, the ability of some of these analogs to establish a H-bond with Ser242 and hydrophobic interactions with Phe234 and Gly238 appears to explain their enhanced affinity as compared to nantenine.

Synthesis, structure-affinity relationships, and modeling of AMDA analogs at 5-HT2A and H1 receptors: structural factors contributing to selectivity

Histamine H(1) and serotonin 5-HT(2A) receptors present in the CNS have been implicated in various neuropsychiatric disorders. 9-Aminomethyl-9,10-dihydroanthracene (AMDA), a conformationally constrained diarylalkyl amine derivative, has affinity for both of these receptors. A structure-affinity relationship (SAFIR) study was carried out studying the effects of N-methylation, varying the linker chain length and constraint of the aromatic rings on the binding affinities of the compounds with the 5-HT(2A) and H(1) receptors. Homology modeling of the 5-HT(2A) and H(1) receptors suggests that AMDA and its analogs, the parent of which is a 5-HT(2A) antagonist, can bind in a fashion analogous to that of classical H(1) antagonists whose ring systems are oriented toward the fifth and sixth transmembrane helices. The modeled orientation of the ligands are consistent with the reported site-directed mutagenesis data for 5-HT(2A) and H(1) receptors and provide a potential explanation for the selectivity of ligands acting at both receptors.

Examination of association of genes in the serotonin system to autism

Autism is characterized as one of the pervasive developmental disorders, a spectrum of often severe behavioral and cognitive disturbances of early development. The high heritability of autism has driven multiple efforts to identify genetic variation that increases autism susceptibility. Numerous studies have suggested that variation in peripheral and central metabolism of serotonin (5-hydroxytryptamine) may play a role in the pathophysiology of autism. We screened 403 autism families for 45 single nucleotide polymorphisms in ten serotonin pathway candidate genes. Although genome-wide linkage scans in autism have provided support for linkage to various loci located within the serotonin pathway, our study does not provide strong evidence for linkage to any specific gene within the pathway. The most significant association (p = 0.0002; p = 0.02 after correcting for multiple comparisons) was found at rs1150220 (HTR3A) located on chromosome 11 ( approximately 113 Mb). To test specifically for multilocus effects, multifactor dimensionality reduction was employed, and a significant two-way interaction (p value = 0.01) was found between rs10830962, near MTNR1B (chromosome11; 92,338,075 bp), and rs1007631, near SLC7A5 (chromosome16; 86,413,596 bp). These data suggest that variation within genes on the serotonin pathway, particularly HTR3A, may have modest effects on autism risk.

Effects of common medications used for sleep disorders

Sleep disorders are common and their diagnosis is becoming more widespread with improved awareness among clinicians and patients. The armamentarium for the pharmacologic treatment of sleep disorders is rapidly growing, demanding that clinicians be aware of their indications, adverse effects, and interactions. As disorders, such as narcolepsy, shift-work sleep disorder, and RLS are more readily identified, pharmacologic treatments for these conditions will also become more common.