Targeting Serotonin1A Receptors for Treating Chronic Pain and Depression

The association of chronic pain with depression is becoming increasingly recognized. Treating both the conditions together is essential for an effective treatment outcome. In this regard, it is important to identify a shared mechanism involved in the association of chronic pain with depression. Central serotonin (5-hydroxytryptamine; 5-HT) neurotransmission has long been known to participate in the processing of signals related to pain. It also plays a key role in the pathogenesis and treatment of depression. Although functional responses to serotonin are mediated via the activation of multiple receptor types and subtypes, the 5-HT1A subtype is involved in the processing of nociception as well as the pathogenesis and treatment of depression. This receptor is located presynaptically, as an autoreceptor, on the perikaryon and dendritic spines of serotonin-containing neurons. It is also expressed as a heteroreceptor on neurons receiving input from serotonergic neurons. This arti-cle targets the 5-HT1A receptors to show that indiscriminate activation of pre and postsynaptic 5-HT1A receptors is likely to produce no therapeutic benefits; biased activation of the 5-HT heteroreceptors may be a useful strategy for treating chronic pain and depression individually as well as in a comorbid condition.

MAOA-uVNTR polymorphism in male recidivist violent offenders in the Indian population

INTRODUCTION

An association of MAOA-uVNTR polymorphism with aggression and violence has been demonstrated in many studies; however, this association is inconclusive due to the allelic variation in different populations. Allelic variants and the frequency of this polymorphism among recidivist violent offenders could provide more information about this complex behaviour. Hence, the association between violence and the polymorphism of variable numbers of tandem repeats located upstream of the MAOA gene needs to be ruled out.

MATERIAL AND METHODS

Identified recidivist violent offenders by various laws of 'Offences against Human Body and Property' of the Indian Penal Code and natives of the southern state of India, Kerala, were the cases. Individuals without a history of any offences, from the same locality, were taken as controls. DNA extracted from the buccal epithelial cells from the subjects was genotyped using PCR methods for identifying MAOA-uVNTR polymorphism.

RESULTS

In the subjects (n = 67), polymorphism in the promoter region of the MAOA gene, which comprises of 30bp repeats, 3.5 and 4.5 repeat alleles were observed statistically significantly (p = 0.015). Both 3.5 and 4.5 repeat alleles were present in the participants belonging to the control group. All the participants belonging to experiment group had 3.5 repeats only.

CONCLUSIONS

This candidate gene-environment interaction (cGxE) may be one of the reasons for the development of psychopathology in violent offenders. This is the first study among offenders in this regard in India, and data generated will be a significant contribution to the aetiology of various psychiatric disorders and population-specific genome database.

Estrogen and Serotonin: Complexity of Interactions and Implications for Epileptic Seizures and Epileptogenesis

A burgeoning literature documents the confluence of ovarian steroids and central serotonergic systems in the in-junction of epileptic seizures and epileptogenesis. Estrogen administration in animals reduces neuronal death from seizures by up-regulation of the prosurvival molecule i.e. Bcl-2, anti-oxidant potential and protection of NPY interneurons. Serotonin modulates epileptiform activity in either direction i.e administration of 5-HT agonists or reuptake inhibitors leads to the acti-vation of 5-HT3 and 5-HT1A receptors tending to impede focal and generalized seizures, while depletion of brain 5-HT along with the destruction of serotonergic terminals leads to expanded neuronal excitability hence abatement of seizure threshold in experimental animal models. Serotonergic neurotransmission is influenced by the organizational activity of ster-oid hormones in the growing brain and the actuation effects of steroids which come in adulthood. It is further established that ovarian steroids bring induction of dendritic spine proliferation on serotonin neurons thus thawing a profound effect on sero-tonergic transmission. This review features 5-HT1A and 5-HT3 receptors as potential targets for ameliorating seizure-induced neurodegeneration and recurrent hypersynchronous neuronal activity. Indeed 5-HT3 receptors mediate cross-talk be-tween estrogenic and serotonergic pathways, and could be well exploited for combinatorial drug therapy against epileptogen-esis.

Study of the Effects of L-tryptophane Nanoparticles on Motor Behavior in Alzheimer's Experimental Models

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the progressive and incapacitating decay of cognitive, neuropsychiatric, and behavioral manifestations. L-tryptophan is the precursor amino acid of serotonin, which is a neurotransmitter responsible for mood balance and the sense of well-being and can be administered in the form of nanoparticles.

OBJECTIVE

This study analyzed the effectiveness of L-tryptophan nanoparticles and L-tryptophan on behavioral physiological alterations resulting from AD in animal models.

METHODS

The sample consisted of 50 Rattus norvegicus rats, divided in 10 groups with 5 animals each: one negative control (NC), three positive control groups (C3, C7, and C21), three groups treated with L-tryptophan nanoparticles (T3N, T7N, and T21N) at the concentration of 1.5 mg, and three groups treated with L-tryptophan (T3L, T7L, and T21L) at the concentration of 1.5 mg. The rats underwent stereotactic surgery to induce AD through the injection of amyloid beta-amyloid peptide1-42 in the intracerebroventricular region. All rats were submitted to pre- and post-surgery and post-treatment motor behavior evaluation through the Later Water Maze (LWM) and elevated cross-labyrinth (ECL). Histological analysis was performed to verify the presence of senile plaques, and the statistical analysis used the unpaired T-test.

RESULTS

Significant intergroup differences were observed in some of the evaluated parameters between treated and untreated groups.

CONCLUSION

It was concluded that the treatment with L-tryptophan nanoparticles was beneficial to improve behavioral reactions in the Alzheimer's model.

Pharmacophore Comparison and Development of Recently Discovered Long Chain Arylpiperazine and Sulfonamide Based 5-HT7 Ligands

The serotonin system exerts its effects on the CNS and many peripheral systems. Of the 14 serotonin receptors, the 5-HT7 receptor is the most recently discovered. The 5-HT7 receptor has been shown to be involved in stress reduction, depression, and nociceptive control. Despite the 20 years since the discovery of 5-HT7R, there are still few truly selective ligands. Two of the common scaffolds for 5-HT7R ligands are long chain arylpiperazines (LCAPs) and sulfonamide containing compounds. This review focuses on recently developed (2014-2016) 5-HT7R ligands, their selectivity for the receptor, and suggests the possible new pharmacophore models for these ligands.

Clozapine-induced obsessive-compulsive symptoms in schizophrenia: a critical review

Obsessive-compulsive disorder (OCD) is rarely associated with schizophrenia, whereas 20 to 30% of schizophrenic patients, suffer from comorbid obsessive-compulsive symptoms (OCS). So far no single pathogenetic theory convincingly explained this fact suggesting heterogeneous subgroups. Based on long-term case observations, one hypothesis assumes that second-onset OCS in the course of schizophrenia might be a side effect of second generation antipsychotics (SGA), most importantly clozapine (CLZ). This review summarizes the supporting epidemiological and pharmacological evidence: Estimations on prevalence of OCS increase in more recent cross-sectional studies and in later disease stages. Longitudinal observations report the de novo-onset of OCS under clozapine treatment. This association has not been reported with first generation antipsychotics (FGA) or SGAs with mainly dopaminergic mode of action. Finally, significant correlations of OCS-severity with duration of treatment, dose and serum levels suggest clozapine-induced OCS. However, supposed causal interactions need further verifications. It is also unclear, which neurobiological mechanisms might underlie the pathogenetic process. Detailed genotypic and phenotypic characterizations of schizophrenics with comorbid OCS regarding neurocognitive functioning and activation in sensitive tasks of functional magnetic imaging are needed. Multimodal large-scaled prospective studies are necessary to define patients at risk for second-onset OCS and to improve early detection and therapeutic interventions.

IL1beta- and LPS-induced serotonin secretion is increased in EC cells derived from Crohn's disease

Gut mucosal enterochromaffin (EC) cells are regarded as key regulators of intestinal motility and fluid secretion via secretion of serotonin (5HT), are increased in numbers in mucosal inflammation and located in close proximity to immune cells. We examined whether interleukin (IL)1beta and Escherichia coli lipopolysaccharide (LPS) induced EC cell 5HT release through Toll-like/IL-1 (TIL) receptor activation, nuclear factor kappa B (NFkappaB) and mitogen-activated protein kinase (MAPK) phosphorylation and evaluated whether somatostatin could inhibit this phenomenon. Pure (>98%) human intestinal EC cells were isolated by fluorescent activated cell sorting from preparations of normal (n = 5) and Crohn's colitis (n = 6) mucosa. 5HT release was measured (ELISA), and NFkappaB and ERK phosphorylation quantitated (ELISA) in response to IL1beta and LPS. 5HT secretion was increased by both E. coli LPS (EC(50) = 5 ng mL(-1)) and IL1beta (EC(50) = 0.05 pmol L(-1)) >2-fold (P < 0.05) in Crohn's EC cells compared with normal EC cells. Secretion was reversible by the TLR4 antagonist, E. coli K12 LPS (IC(50) = 12 ng mL(-1)) and the IL1beta receptor antagonist (ILRA; IC(50) = 3.4 ng mL(-1)). IL1beta caused significant (P < 0.05) NFkappaB and MAPK phosphorylation (40-55%). The somatostatin analogue, lanreotide inhibited IL1beta-stimulated secretion in Crohn's (IC(50) = 0.61 nmol L(-1)) and normal EC cells (IC(50) = 1.8 nmol L(-1)). Interleukins (IL1beta) and bacterial products (E. coli LPS) stimulated 5HT secretion from Crohn's EC cells via TIL receptor activation (TLR4 and IL1beta). Immune-mediated alterations in EC cell secretion of 5HT may represent a component of the pathogenesis of abnormal bowel function in Crohn's disease. Inhibition of EC cell-mediated 5HT secretion may be an alternative therapeutic strategy in the amelioration of inflammatory bowel disease symptomatology.