In Vivo Imaging of [60]Fullerene-Based Molecular Spherical Nucleic Acids by Positron Emission Tomography.

18F-Labeled [60]fullerene-based molecular spherical nucleic acids (MSNAs), consisting of a human epidermal growth factor receptor 2 (HER2) mRNA antisense oligonucleotide sequence with a native phosphodiester and phosphorothioate backbone, were synthesized, site-specifically labeled with a positron emitting fluorine-18 and intravenously administrated via tail vein to HER2 expressing HCC1954 tumor-bearing mice. The biodistribution of the MSNAs was monitored in vivo by positron emission tomography/computed tomography (PET/CT) imaging. MSNA with a native phosphodiester backbone (MSNA-PO) was prone to rapid nuclease-mediated degradation, whereas the corresponding phosphorothioate analogue (MSNA-PS) with improved enzymatic stability showed an interesting biodistribution profile in vivo. One hour after the injection, majority of the radioactivity was observed in spleen and liver but also in blood with an average tumor-to-muscle ratio of 2. The prolonged radioactivity in blood circulation may open possibilities to the targeted delivery of the MSNAs.

Tasipimidine-the pharmacological profile of a novel orally active selective α2A-adrenoceptor agonist.

The pharmacological profile of tasipimidine, a novel orally active α2-adrenoceptor agonist developed for situational anxiety and fear in dogs, was studied in various in vitro and in vivo models. In the cell assays, tasipimidine demonstrated binding affinity and full agonism on the human α2A-adrenoceptors with a pEC50 of 7.57, while agonism on the α2B-and α2C-adrenoceptors and the rodent α2D-adrenoceptor was weaker, resulting in pEC50 values of 6.00, 6.29 and 6.56, respectively. Tasipimidine had a low binding affinity on the human α1-adrenoceptors. It had no functional effects in the LNCaP cells expressing endogenously the human α1A-adrenoceptors but was a weak agonist in the Chem-1 cells coexpressing Gα15 protein and α1A-adrenoceptors. In the recombinant CHO cells, although tasipimidine was a weak partial agonist in the inositol monophosphate accumulation assay, it was a full agonist in the intracellular [Ca2+] assay. No functional effects were observed on the human α1B-adrenoceptor, whereas in the rat α1A and α1B-adrenoceptors, tasipimidine was a weak partial agonist. In the rat vas deferens preparations, tasipimidine was a full agonist on the α2D-adrenoceptor but weak partial agonist on the α1-adrenoceptor. The receptor profile of tasipimidine indicated few secondary targets, and no functional effects were observed. Sedative effects of tasipimidine were demonstrated in vivo by the reduced acoustic startle reflex in rats with subcutaneous doses and decreased spontaneous locomotor activity in mice with subcutaneous and higher oral doses. It may be concluded that tasipimidine is an orally active and selective α2A-adrenoceptor agonist.

Sexual Incentive Motivation and Copulatory Behavior in Male Rats Treated With the Adrenergic α2-Adrenoceptor Agonists Tasipimidine and Fadolmidine: Implications for Treatment of Premature Ejaculation.

BACKGROUND: Premature ejaculation is the most common sexual dysfunction in young men, and it often leads to reduced relationship satisfaction and quality of life. AIM: To determine the role of central and peripheral α2-adrenoceptors in the control of ejaculation and sexual incentive motivation in rats. METHODS: Sexual incentive motivation was studied in a large arena in which a male subject could choose between approaching and remaining close to a sexually receptive female or another male. Sexual behavior was studied in standard observation cages in which a male was allowed to freely interact with a receptive female for 30 minutes. Two highly selective agonists at the α2-adrenoceptors, tasipimidine and fadolmidine, were administered before the tests. Low peripheral doses of fadolmidine have been reported to have effects mainly outside of the central nervous system, whereas at large doses also the central effects are evident. OUTCOMES: The time spent close to the receptive female in relation to the time spent with the male and measures of ambulatory activity were obtained from the test for sexual incentive motivation, while the habitual parameters of sexual behavior were recorded with the copulation test. RESULTS: Tasipimidine prolonged ejaculation latency and the interintromission interval at the dose of 200 µg/kg when data from fast-ejaculating rats were used. No other sexual parameter was modified. A dose of 100 µg/kg was ineffective. There was no consistent effect on sexual incentive motivation, although modest sedation was observed. Fadolmidine, a drug that does not easily penetrate the blood-brain barrier, had no effect on sexual incentive motivation at any of the doses used (3, 30, and 100 µg/kg). The largest dose had clear sedative effects. The lower doses had no systematic effect on sexual behavior, not even when only fast or very fast ejaculating males were analyzed. CLINICAL TRANSLATION: The findings are relevant to the search for treatments for premature ejaculation that are specific enough to selectively delay ejaculation. STRENGTHS & LIMITATIONS: The procedures used here are standard in the field and yield the most reliable data. Whether the effects observed in male rats are directly transferrable to men can only be determined through clinical studies. CONCLUSION: The observation that drugs acting at central but not peripheral α2-adrenoceptors prolong ejaculation latency without affecting any other parameter of sexual behavior or sexual incentive motivation suggests that this kind of drug may be suitable for treating premature ejaculation. Jyrki L., Elisa V.-A., Xi C., et al. Sexual Incentive Motivation and Copulatory Behavior in Male Rats Treated With the Adrenergic α2-Adrenoceptor Agonists Tasipimidine and Fadolmidine: Implications for Treatment of Premature Ejaculation. J Sex Med 2021;18:1677-1689.

Characterization of Urothelial Inclusions in Male Wistar Han Rats Treated Orally With the Novel α2A-Adrenoceptor Agonist Tasipimidine.

Intracellular inclusions were observed in urinary bladder epithelium of male Wistar rats, following oral treatment with high doses of the α2A-adrenoceptor agonist tasipimidine for 28 days. No cell death or inflammation was associated with the brightly eosinophilic inclusions. Electron microscopy (EM) studies showed that the inclusions represented intact or fragmented red blood cells (RBC) resulting from erythrophagocytosis, further supported by the presence of iron in urothelial cells. In addition, scattered iron-positive macrophages were observed in the submucosa and muscle layer, indicating microvascular leakage, as no major hemorrhage was evident. Despite the presence of inclusions, the urothelium showed normal uroplakin III distribution, normal cell turnover, and an absence of α-2u-globulin. It is, therefore, concluded that the inclusions were not associated with urothelial damage or increased renewal of the epithelium. This finding shows also that urothelial cells have the capability to phagocytize and break down RBCs originating from submucosal microvascular leakage. Similar changes were not observed in tasipimidine-treated beagle dogs (28 days), suggesting these findings were rat specific. The leakage of RBCs into the urothelium is suggested to be a consequence of exaggerated pharmacology leading to vasoconstriction of submucosal blood vessels in combination with transient increased bladder distension and pressure.

Fadolmidine - Favourable adverse effects profile for spinal analgesia suggested by in vitro and in vivo models.

Fadolmidine is an α2-adrenoceptor full agonist developed for spinal analgesia with a local mode of action. The purpose of this study was to demonstrate the safety of fadolmidine on known α2-adrenoceptor-related effects: kidney function, urodynamics and cardiovascular variables. Furthermore, the binding affinity of fadolmidine for the 5-HT3 receptor prompted functional studies on 5-HT3. According to the binding affinity data, fadolmidine demonstrated partial agonism on the 5-HT3 receptor in transfected cells and in guinea pig ileum preparation. However, intravenous (IV) fadolmidine did not produce any 5-HT3-related hemodynamic effects in anaesthetised rats. In urodynamic studies, intrathecal (IT) fadolmidine interrupted volume-evoked voiding cycles and induced overflow incontinence at high concentrations in anaesthetised rats; however, at the analgesic dose range, the effects were mild. The effects of fadolmidine on kidney function were studied in conscious rats after IV and IT dosing. While IT fadolmidine increased dose-dependent urine output, sodium ion concentration, IV doses increased only sodium ion concentration The effects of IT fadolmidine on heart rate (HR), mean arterial pressure (MAP) and sedation were evaluated in the home cage and in the open field using a telemetry system. In resting conditions, fadolmidine decreased HR dose-dependently and increased initial MAP, whereas in actively moving rats, there were no effects at analgesic doses. The results suggest that at anticipated analgesic clinical doses, IT fadolmidine provides analgesia without significant adverse effects on sedation, MAP or HR and with only modest effects on kidney function and urodynamics.

Pharmacological characterisation of a structurally novel α2C-adrenoceptor antagonist ORM-10921 and its effects in neuropsychiatric models.

The α2-adrenoceptors (ARs) are important modulators of a wide array of physiological responses. As only a few selective compounds for the three α2-AR subtypes (α2A , α2B and α2C ) have been available, the pharmacological profile of a new α2C-selective AR antagonist ORM-10921 is reported. Standard in vitro receptor assays and antagonism of α2, and α1-AR agonist-evoked responses in vivo were used to demonstrate the α2C-AR selectivity for ORM-10921 which was tested in established behavioural models related to schizophrenia and cognitive dysfunction with an emphasis on pharmacologically induced hypoglutamatergic state by phencyclidine or MK-801. The Kb values of in vitro α2C-AR antagonism for ORM-10921 varied between 0.078-1.2 nM depending on the applied method. The selectivity ratios compared to α2A-AR subtype and other relevant receptors were 10-100 times in vitro. The in vivo experiments supported its potent α2C-antagonism combined with only a weak α2A-antagonism. In the pharmacodynamic microdialysis study, ORM-10921 was found to increase extracellular dopamine levels in prefrontal cortex in the baseline conditions. In the behavioural tests, ORM-10921 displayed potent antidepressant and antipsychotic-like effects in the forced swimming test and prepulse-inhibition models analogously with the previously reported results with structurally different α2C-selective AR antagonist JP-1302. Our new results also indicate that ORM-10921 alleviated the NMDA-antagonist-induced impairments in social behaviour and watermaze navigation. This study extends and further validates the concept that α2C -AR is a potential therapeutic target in CNS disorders such as schizophrenia or Alzheimer's disease and suggests the potential of α2C-antagonism to treat such disorders.

Effect of dexmedetomidine on ejaculatory behavior and sexual motivation in intact male rats.

Premature ejaculation is the most common sexual disorder in young men. Consequently, there is an intense search for efficient and safe pharmacological treatments. Insofar, almost no effective treatment with acute effects is available. In this study, we evaluated the effects of the noradrenergic α(2) receptor agonist dexmedetomidine on sexual incentive motivation and copulatory behavior in male rats. Sexual incentive motivation was tested in a large rectangular arena connected to two small incentive stimulus cages containing either a male or sexually receptive female rat. There was no sexual interaction possible between the experimental subjects and the incentives during this test. Approach to the incentives constituted the measure of sexual incentive motivation. After the sexual incentive motivation test, the subjects were tested for copulatory behavior in a regular copulation test for 30min. Doses of 0.1 and 1µg/kg of dexmedetomidine (i.p.) had no effect on any of the indices of locomotor activity or on parameters of sexual incentive motivation. With regard to copulatory behavior, it was found that the dose of 1µg/kg prolonged the latency to the first ejaculation, while the latency to second ejaculation showed a tendency to increase. The absence of an effect on indices of sexual incentive motivation or general activity showed that the actions of dexmedetomidine in this study were limited to ejaculatory mechanisms. Insofar as the ejaculation latency in the male rat is predictive of prolonged ejaculation latency in men, it can be proposed that dexmedetomidine is of potential utility for the treatment of premature ejaculation.

Pharmacological profile of intrathecal fadolmidine, a alpha2-adrenoceptor agonist, in rodent models.

The present experiments compared the peripheral and central pharmacological effects of three alpha(2)-adrenoceptor agonists: fadolmidine, clonidine, and dexmedetomidine after single intrathecal bolus injections at analgesic dose level in rats. Effects on mydriasis and cardiovascular functions were studied in anaesthetised rats, the effects on sedation/motor performance, body temperature, and gastrointestinal motility were evaluated in conscious rats, and also the effects on brain biogenic amines were studied. All compounds caused dose-dependent mydriasis, a decrease in blood pressure and heart rate, sedation, hypothermia, and inhibition of gastrointestinal transit, but in contrast to the analgesic effects, dexmedetomidine and clonidine were much more potent than fadolmidine. In accordance with the other systemic effects, dexmedetomidine and clonidine, but not fadolmidine, reduced the turnover of the monoamine neurotransmitters, noradrenaline and serotonin, in brain at the analgesic dose. The difference in the systemic effect profile between fadolmidine and clonidine or dexmedetomidine is most probably explained by differences in their ability to spread from the site of administration at the lumbar level into the periphery and/or the brain and further the concentrations of the compounds in the side of action. These results supports that intrathecally administered fadolmidine could have potential to be used as an analgesic agent with less subraspinal or spinal adverse effects at analgesic doses than dexmedetomidine and clonidine.

In vitro and in vivo profiling of fadolmidine, a novel potent alpha(2)-adrenoceptor agonist with local mode of action.

Alpha2-adrenergic receptors (alpha2-adrenoceptors) mediate various physiological actions of endogenous catecholamines in the central and peripheral nervous systems being involved in alertness, heart rate regulation, vasomotor control and nociceptive processing. In the present study, the pharmacological profile of a novel alpha2-adrenoceptor agonist, fadolmidine, was studied in various in vitro and in vivo assays and compared to the well characterised alpha2-adrenoceptor agonist, dexmedetomidine. Fadolmidine displayed high affinity and full agonist efficacy at all three human alpha2-adrenoceptor subtypes (A, B and C) in transfected CHO cells with EC50 values (nM) of 0.4, 4.9 and 0.5, respectively. Fadolmidine inhibited also electrically evoked contractions in rat vas deferens demonstrating the activation of rodent presynaptic alpha2D-adrenoceptors with an EC50 value of 6.4 nM. Moreover, fadolmidine was a full agonist at human alpha1A-adrenoreceptor (EC50 value 22 nM) and alpha1B-adrenoreceptor (EC50 value 3.4 nM) in human LNCaP cells and transfected HEK cells, respectively. Agonism at the alpha1-adrenoceptor was also observed in rat vas deferens preparations although at lower potency (EC50 value 5.6 microM). Fadolmidine demonstrated potent alpha2-adrenoceptor agonist activity also in vivo by inhibiting electrically induced tachycardia in pithed rats and increasing mean arterial pressure in anaesthetised rats. However, after systemic administration, fadolmidine had considerably weaker CNS-mediated effects (mydriasis and sedation) compared to dexmedetomidine possibly due to limited penetration through the blood brain barrier by fadolmidine. In a conclusion, fadolmidine is a potent full agonist at all three alpha2-adrenoceptor subtypes with a pharmacological profile compatible with a therapeutic value e.g. after spinal administration.