Vilazodone does not inhibit sexual behavior in male rats in contrast to paroxetine: A role for 5-HT1A receptors?

Computational Chemistry in Structure-Based Solute Carrier Transporter Drug Design: Recent Advances and Future Perspectives

Solute carrier transporters (SLCs) are a class of important transmembrane proteins that are involved in the transportation of diverse solute ions and small molecules into cells. There are approximately 450 SLCs within the human body, and more than a quarter of them are emerging as attractive therapeutic targets for multiple complex diseases, e.g., depression, cancer, and diabetes. However, only 44 unique transporters (∼9.8% of the SLC superfamily) with 3D structures and specific binding sites have been reported. To design innovative and effective drugs targeting diverse SLCs, there are a number of obstacles that need to be overcome. However, computational chemistry, including physics-based molecular modeling and machine learning- and deep learning-based artificial intelligence (AI), provides an alternative and complementary way to the classical drug discovery approach. Here, we present a comprehensive overview on recent advances and existing challenges of the computational techniques in structure-based drug design of SLCs from three main aspects: (i) characterizing multiple conformations of the proteins during the functional process of transportation, (ii) identifying druggability sites especially the cryptic allosteric ones on the transporters for substrates and drugs binding, and (iii) discovering diverse small molecules or synthetic protein binders targeting the binding sites. This work is expected to provide guidelines for a deep understanding of the structure and function of the SLC superfamily to facilitate rational design of novel modulators of the transporters with the aid of state-of-the-art computational chemistry technologies including artificial intelligence.

Extract of Pfaffia glomerata Ameliorates Paroxetine-Induced Sexual Dysfunction in Male Mice and the Characterization of Its Phytoconstituents by UPLC-MS

Pfaffia glomerata extract (PGE) has a variety of biological activities. However, its ameliorative effect on and exact working mechanism in male sexual dysfunction are still poorly understood. This study aims to evaluate the ameliorative effect of PGE on paroxetine (PRX)-induced sexual dysfunction in male mice and uses molecular docking technology to investigate its underlying mechanism. In this work, PRX-induced sexual dysfunction was caused and PGE was gavaged in mice for 28 days. The results show that PGE significantly improved the sexual performance of mice and reduced the damage to testicular tissues. Further studies showed that PGE restored serum sex hormones to normal levels and increased nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) levels as well as nitric oxide synthase (NOS) activity in penile tissues, while also decreasing phosphodiesterase-5 (PDE-5) activity, thereby maintaining normal penile erection in mice. In addition, PGE improved the activities of enzymes (LDH, ACP, and ALP) related to energy metabolism in the testis and significantly increased sperm count and viability in mice. Furthermore, the molecular docking results show that all eight compounds in PGE could form a stable complex with PDE-5 and inhibit the activity of PDE-5. In conclusion, PGE had an ameliorative effect on PRX-induced sexual dysfunction, suggesting that PGE has a potential protective effect on male sexual health.

The pathophysiology of Post SSRI Sexual Dysfunction - Lessons from a case study

BACKGROUND

Although Post-SSRI Sexual Dysfunction (PSSD) has finally been recognized by the European Medicines Agency as a medical condition that can outlast discontinuation of SSRI and SNRI antidepressants, this condition is still largely unknown by patients, doctors, and researchers, and hence, poorly understood, underdiagnosed, and undertreated.

OBJECTIVE

Becoming familiar with the symptomatology of PSSD and understanding the underlying mechanisms and treatment options.

METHOD

We applied a design thinking approach to innovation to 1) provide insights into the medical condition as well as the personal needs and pains of a targeted patient; and 2) generate ideas for new solutions from the perspective of this particular patient. These insights and ideas informed a literature search on the potential pathophysiological mechanisms that could underlie the patient's symptoms.

RESULTS

The 55-year-old male patient developed symptoms of low libido, delayed ejaculation, erectile dysfunction, 'brain zaps', overactive bladder and urinary inconsistency after discontinuation of the SNRI venlafaxine. In many of these symptoms a dysregulation in serotonergic activity has been implicated, with an important role of 5-HT_1A receptor downregulation and possible downstream effects on neurosteroid and oxytocin systems.

CONCLUSIONS

The clinical presentation and development of symptoms are suggestive of PSSD but need further clinical elaboration. Further knowledge of post-treatment changes in serotonergic - and possibly noradrenergic - mechanisms is required to improve our understanding of the clinical complaints and to inform appropriate treatment regimes.

Effects of paroxetine treatment and its withdrawal on neurosteroidogenesis

Selective serotonin reuptake inhibitors (SSRI) show high efficacy in treating depression, however during treatment side effects, like for instance sexual dysfunction, may appear, decreasing compliance. In some cases, this condition will last after drug discontinuation, leading to the so-called post-SSRI sexual dysfunction (PSSD). The etiology of PSSD is still unknown, however a role for neuroactive steroids may be hypothesized. Indeed, these molecules are key physiological regulators of the nervous system, and their alteration has been associated with several neuropathological conditions, including depression. Additionally, neuroactive steroids are also involved in the control of sexual function. Interestingly, sexual dysfunction induced by SSRI treatment has been also observed in animal models. On this basis, we have here evaluated whether a subchronic treatment with paroxetine for two weeks and/or its withdrawal (i.e., a month) may affect the levels of neuroactive steroids in brain areas (i.e., hippocampus, hypothalamus, and cerebral cortex) and/or in plasma and cerebrospinal fluid of male rats. Data obtained indicate that the SSRI treatment alters neuroactive steroid levels and the expression of key enzymes of the steroidogenesis in a brain tissue- and time-dependent manner. Indeed, these observations with the finding that plasma levels of neuroactive steroids are not affected suggest that the effect of paroxetine treatment is directly on neurosteroidogenesis. In particular, a negative impact on the expression of steroidogenic enzymes was observed at the withdrawal. Therefore, it is possible to hypothesize that altered neurosteroidogenesis may also occur in PSSD and consequently it may represent a possible pharmacological target for this disorder.

The Sexual Motivation of Male Rats as a Tool in Animal Models of Human Health Disorders

Normal or dysfunctional sexual behavior seems to be an important indicator of health or disease. Many health disorders in male patients affect sexual activity by directly causing erectile dysfunction, affecting sexual motivation, or both. Clinical evidence indicates that many diseases strongly disrupt sexual motivation and sexual performance in patients with depression, addiction, diabetes mellitus and other metabolic disturbances with obesity and diet-related factors, kidney and liver failure, circadian rhythm disorders, sleep disturbances including obstructive sleep apnea syndrome, developmental and hormonal disorders, brain damages, cardiovascular diseases, and peripheral neuropathies. Preclinical studies of these conditions often require appropriate experimental paradigms, including animal models. Male sexual behavior and motivation have been intensively investigated over the last 80 years in animal rat model. Sexual motivation can be examined using such parameters as: anticipatory behavior and 50-kHz ultrasonic vocalizations reflecting the emotional state of rats, initiation of copulation, efficiency of copulation, or techniques of classical (pavlovian) and instrumental conditioning. In this review article, we analyze the behavioral parameters that describe the sexual motivation and sexual performance of male rats in the context of animal experimental models of human health disorders. Based on analysis of the parameters describing the heterogeneous and complex structure of sexual behavior in laboratory rodents, we propose an approach that is useful for delineating distinct mechanisms affecting sexual motivation and sexual performance in selected disease states and the efficacy of therapy in preclinical investigations.

Modified Suanzaorentang Had the Treatment Effect for Generalized Anxiety Disorder for the First 4 Weeks of Paroxetine Medication: A Pragmatic Randomized Controlled Study

Background. Paroxetine does not show satisfactory therapeutic effect for generalized anxiety disorder (GAD) patients for the first 2–4 weeks of medication. Diazepam is always concurrently used although it has some shortcomings such as physical dependence and withdrawal reactions. In this study, we aimed to identify whether modified Suanzaorentang (MSZRT), a combined Chinese formula including Suanzaorentang (SZRT) and Zhizichitang (ZZCT), could control the anxiety of GAD for the first 4 weeks of paroxetine medication. Methods. 156 GAD patients were randomized to the treatment of paroxetine, paroxetine-diazepam, or paroxetine-MSZRT for 4 weeks. Hamilton Anxiety Scale (HAMA) Test and Self-Rating Anxiety Scale (SAS) Test were determined each week as the evaluation of clinical efficacy. Adverse events (AEs) were also closely observed by performing the Treatment Emergent Symptom Scale (TESS) Test. Results. Both paroxetine-MSZRT and paroxetine-diazepam decreased more HAMA and SAS total scores than paroxetine from weeks 1 to 3. Paroxetine-MSZRT as well as paroxetine-diazepam had an obviously higher onset rate than paroxetine in each week. After 4 weeks' treatment, the overall effectiveness rate in the paroxetine-MSZRT group (90.00%) was obviously higher than those of the paroxetine group (74.42%) but did not significantly differ from the paroxetine-diazepam group (93.88%). Conclusion. MSZRT had the treatment effect for GAD when paroxetine was used for the first 4 weeks.