5-HT1A Serotonergic, α-Adrenergic and Opioidergic Receptors Mediate the Analgesic Efficacy of Vortioxetine in Mice.

Vortioxetine is a multimodal antidepressant drug that affects several brain neurochemicals and has the potential to induce various pharmacological effects on the central nervous system. Therefore, we investigated the centrally mediated analgesic efficacy of this drug and the mechanisms underlying this effect. Analgesic activity of vortioxetine (5, 10 and 20 mg/kg, p.o.) was examined by tail-clip, tail-immersion and hot-plate tests. Motor performance of animals was evaluated using Rota-rod device. Time course measurements (30-180 min) showed that vortioxetine (10 and 20 mg/kg) administrations significantly increased the response latency, percent maximum possible effect and area under the curve values in all of the nociceptive tests. These data pointed out the analgesic effect of vortioxetine on central pathways carrying acute thermal and mechanical nociceptive stimuli. Vortioxetine did not alter the motor coordination of mice indicating that the analgesic activity of this drug was specific. In mechanistic studies, pre-treatments with p-chlorophenylalanine (serotonin-synthesis inhibitor), NAN-190 (serotonin 5-HT1A receptor antagonist), α-methyl-para-tyrosine (catecholamine-synthesis inhibitor), phentolamine (non-selective α-adrenoceptor blocker), and naloxone (non-selective opioid receptor blocker) antagonised the vortioxetine-induced analgesia. Obtained findings indicated that vortioxetine-induced analgesia is mediated by 5-HT1A serotonergic, α-adrenergic and opioidergic receptors, and contributions of central serotonergic and catecholaminergic neurotransmissions are critical for this effect.

Adrenergic ß2-receptors mediates visceral hypersensitivity induced by heterotypic intermittent stress in rats.

Chronic visceral pain in patients with irritable bowel syndrome (IBS) has been difficult to treat effectively partially because its pathophysiology is not fully understood. Recent studies show that norepinephrine (NE) plays an important role in the development of visceral hypersensitivity. In this study, we designed to investigate the role of adrenergic signaling in visceral hypersensitivity induced by heterotypical intermittent stress (HIS). Abdominal withdrawal reflex scores (AWRs) used as visceral sensitivity were determined by measuring the visceromoter responses to colorectal distension. Colon-specific dorsal root ganglia neurons (DRGs) were labeled by injection of DiI into the colon wall and were acutely dissociated for whole-cell patch-clamp recordings. Blood plasma level of NE was measured using radioimmunoassay kits. The expression of ß2-adrenoceptors was measured by western blotting. We showed that HIS-induced visceral hypersensitivity was attenuated by systemic administration of a ß-adrenoceptor antagonist propranolol, in a dose-dependent manner, but not by a α-adrenoceptor antagonist phentolamine. Using specific ß-adrenoceptor antagonists, HIS-induced visceral hypersensitivity was alleviated by ß2 adrenoceptor antagonist but not by ß1- or ß3-adrenoceptor antagonist. Administration of a selective ß2-adrenoceptor antagonist also normalized hyperexcitability of colon-innervating DRG neurons of HIS rats. Furthermore, administration of ß-adrenoceptor antagonist suppressed sustained potassium current density (IK) without any alteration of fast-inactivating potassium current density (IA). Conversely, administration of NE enhanced the neuronal excitability and produced visceral hypersensitivity in healthy control rats, and blocked by ß2-adrenoceptor antagonists. In addition, HIS significantly enhanced the NE concentration in the blood plasma but did not change the expression of ß2-adrenoceptor in DRGs and the muscularis externa of the colon. The present study might provide a potential molecular target for therapy of visceral hypersensitivity in patents with IBS.

UPLC-MS/MS determination of phentolamine in human plasma and its application to a pharmacokinetic study.

A sensitive and rapid ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed to determine phentolamine in human plasma. Sample preparation was accomplished through a simple liquid-liquid extraction with ethyl acetate. Chromatographic separation was carried out on an Acquity UPLC BEH C18 column using an isocratic mobile phase system composed of acetonitrile and 1% formic acid in water (33:67, v/v) at a flow rate of 0.45 mL/min. Mass spectrometric analysis was performed using a QTrap5500 mass spectrometer coupled with an electro-spray ionization (ESI) source in the positive ion mode. The MRM transitions of m/z 282.1 → 212.0 and m/z 237.1 → 194.2 were used to quantify for phentolamine and carbamazepine (internal standard, IS), respectively. The linearity of this method was found to be within the concentration range of 0.5-100.0 ng/mL with a lower limit of quantification of 0.5 ng/mL. Only 1.0 min was needed for an analytical run. This fully validated method was successfully applied to the pharmacokinetic study after oral administration of 60 mg phentolamine to 20 Chinese healthy male volunteers.

Stability and compatibility of doxofylline with phentolamine mesilate in 0.9% sodium chloride or 5% dextrose injection for intravenous infusion.

WHAT IS KNOWN AND OBJECTIVE: The use of extemporaneously prepared admixtures of drugs must be supported by documentation of their chemical stability. The objective was to assess the physical compatibility and the chemical stability of doxofylline with phentolamine mesilate in 0.9% sodium chloride or 5% dextrose injection for intravenous infusion. METHODS: Total volumes of 20 and 1 mL of doxofylline solution and phentolamine mesilate solution, respectively, were added to 250 mL polyolefin bags containing 5% dextrose injection or 0.9% sodium chloride injection. Bags were stored for 24 h at 20-25 °C. Chemical compatibility was measures with high-performance liquid chromatography, and physical compatibility was determined visually. RESULTS: The samples were clear and colourless when viewed in normal fluorescent room light. The pH value and particulate content of the admixtures exhibited little change. The retentions of the initial concentration of doxofylline and phentolamine mesilate in the admixtures were within 97-105%. Doxofylline and phentolamine mesilate were stable in 5% dextrose injection or in 0.9% sodium chloride for up to 24 h at 20-25 °C. WHAT IS NEW AND CONCLUSION: Doxofylline and phentolamine mesilate mixed in both 5% dextrose injection and 0.9% sodium chloride injection in 250 mL multilayer polyolefin bags at concentrations of 0.74 mg/mL and 36.9 µg/mL, respectively, were stable for up to 24 h at 20-25 °C.

Flow-injection chemiluminescence determination of phentolamine based on its enhancing effect on the luminol-potassium ferricyanide system.

It was found that the light emission produced by the oxidation of luminol by potassium ferricyanide in the basic medium was enhanced by phentolamine, a drug recently used to treatment of male and female sexual dysfunction. The optimum conditions for this chemiluminescent reaction were studied in detail by a flow-injection system. A new, simple and rapid method has been developed under the optimum conditions for determination of phentolamine. This method has the advantages of high sensitivity, good reproducibility and low detection limit. On the basis of investigation of chemiluminescent, fluorescent and UV spectra of phentolamine in basic solution containing potassium ferricyanide and luminol, a possible mechanism of this reaction was proposed. In the optimum conditions, CL intensities are proportional to concentrations of the phentolamine in the 0.01-1 microg/mL range. The limit of detection is 3.0 ng/mL for phentolamine. The method has been applied to the determination of phentolamine in the commercial preparations, synthetic samples and biological fluids with satisfactory results.

Three-dimensional pharmacophore hypotheses for the locust neuronal octopamine receptor (OAR3). Part 2: agonists.

Three-dimensional pharmacophore hypotheses were built from a set of 43 agonists against octopamine receptor class 3 (OAR3) in locust nervous tissue. Among the 10 chemical-featured models generated by program Catalyst/Hypo, a hypothesis including hydrogen-bond acceptor (HBA), hydrophobic (Hp), and hydrophobic aliphatic (HpA1) features was considered to be important and predictive in evaluating OAR3 agonists. While the ideal and null hypotheses had a cost of 156.40 and 239.20, respectively, the 10 resulting hypotheses possessed costs from 169.89 to 175.81. The best hypothesis that was confirmed to have a 95% chance of true correlation yielded a low RMS of 0.757 and high regression r of 0.933. Active agonists mapped well onto all the features of the hypothesis such as HBA, Hp, and HpA1. On the other hand, inactive compounds were shown to be difficult to achieve the energetically favorable conformation which is found in the active molecules in order to fit the 3-D chemical feature pharmacophore models.

Vasoactive cocktails for erectile dysfunction: chemical stability of PGE1, papaverine and phentolamine.

PURPOSE: Vasoactive cocktails are widely used in diagnosing and treating erectile dysfunction, especially in poor responders to prostaglandin E1 (PGE1). However, very little information as to their chemical interactions and stability is available, despite the huge amount of published work regarding their clinical efficacy. Obviously, medical and legal problems are involved. MATERIALS AND METHODS: We analyzed four kinds of vasoactive cocktails, composed of papaverine, phentolamine and PGE1 in different combinations, using High Performance Liquid Chromatography analysis after 5 to 60 days of storage at temperatures between 2 and 8C. SPSS MANOVA analysis and a t-test for paired samples were used for statistical purposes. RESULTS: Papaverine and phentolamine concentrations showed no significant variations during the 2 month study, ranging from a minimum of 96.75+/-1.20 to a maximum of 103.00+/-0.20% of the starting values. In the same period, PGE1 showed an accelerated degradation profile, reaching concentration values, after 60 days, of 76.00+/-2.28% and 70.20+/-2.02% when added to phentolamine or papaverine respectively and 70.00+/-2.40% with both. CONCLUSIONS: Papaverine and phentolamine are characterized by chemical stability when blended together or with PGE1. Papaverine and/or phentolamine increase the naturally occurring degradation of PGE1 in physiological solution. This effect is most evident in the first 10 days. Papaverine has the greatest deteriorating effect on PGE1. A safe and proper use of these cocktails should take into account the variations of PGE1 concentration.

Pharmacological characterization of alpha-adrenoceptors in the bovine median caudal artery.

This study was initiated to characterize alpha-adrenoceptors in the isolated bovine median caudal (tail) artery preparation for use as a model of blood vessels in the extremities of cattle. Prazosin shifted the concentration-response relationship for noradrenaline and phenylephrine to the right with pA2 values of 8.74 and 9.04, respectively. Against noradrenaline, phentolamine yielded a pA2 of 7.36. The concentration-response relationship for medetomidine was not inhibited by rauwolscine or idazoxan. The noradrenaline KA was 3.11 microM. These results suggest that catecholamines elicit alpha-adrenoceptor-mediated contractions primarily through alpha1-adrenoceptors and not alpha2-adrenoceptors.

[Investigations on the stability of therapeutic drugs derived from imidazole. XII. Qualitative and quantitative stability evaluation of phentolamine hydrochloride solutions]. / Badania trwalosci srodków leczniczychpochodnych imidazoliny.XII. Jakosciowa i ilosciowa ocena trwalosci roztworów chlorowodorku fentolaminy.

Hydrolysis of phentolamine hydrochloride in aqueous solutions, and at pH 1.0 and pH 8.0 was studied by means of thin-layer chromatography. A spectrophotometric method for quantitative assessment of phentolamine hydrochloride hydrolysis has been elaborated, and thermodynamic parameters of this reaction were determined.