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Introduction: Ligands of adenosine A1Rs are potential candidates for the development of drugs for the treatment of paroxysmal supraventricular tachycardia, angina pectoris, hypertriglyceridemia, type 2 diabetes mellitus, neuropathic pain, and heart failure. At the same time, there is a deficiency of drugs that can regulate the functions of A1 receptors. A number of A1-antagonists are at the various stages of clinical trials; other drugs are not very selective or are characterized by an insufficient breadth of their therapeutic action. Therefore, the search for new medicinal compounds for the prevention and treatment of A1-depended diseases among nitro derivatives of tetrazolo[1,5-a]pyrimidine and 1,2,4-triazolo[1,5-a]pyrimidine is of scientific interest. Materials and methods: The search for active compounds was carried out by in silico and in vitro methods. At the first stage, a computer forecast of A1-antagonistic activity was carried out using the Microcosm BioS software. At the second stage, the prediction results were verified in vitro in a model of isolated mouse atria. Results and discussion: Based on the results of the prediction by the method of maximum similarity to standards, the most active compounds III, VIII, and XVII were selected. After testing the prediction results by the isolated atria method, the compound VIII was characterized by A1-blocking effect in vitro at a concentration of 10 μmol/L. Conclusion: The most promising compound with A1-blocking effect in vitro was identified; it is a derivative of tetrazolo[1,5-a]pyrimidine under the code of VIII. It is of interest for us for further in-depth study of its pharmacological properties.

Context: Salsola imbricata Forssk. (Chenopodiaceae) has folkloric repute for the treatment of various gastrointestinal and respiratory ailments. Objective: The present study investigates spasmolytic and bronchorelaxant effects of S. imbricata. Materials and methods: The crude aqueous-ethanol extract of the aerial parts of S. imbricata and its fractions, in cumulative concentrations (0.01–10 mg/mL), were tested on contractions of isolated rabbit jejunum and tracheal preparations. Furthermore, concentration response curves (CRCs) of Ca+2 and carbachol were constructed in the absence and presence of the extract. Standard organ bath methods were used. Results: The crude extract relaxed spontaneous, K+ (80 mM) and carbachol (1 μM)-induced contractions in jejunum preparations with respective EC50 values of 0.40 (0.35–0.46), 0.69 (0.60–0.79) and 0.66 (0.57–0.75) mg/mL. It shifted Ca+2 CRCs rightward in nonparallel manner. In isolated tracheal preparations, the crude extract caused relaxation of K+ (80 mM) and carbachol (1 μM)-induced contractions with EC50 values of 0.86 (0.75–0.98) and 0.74 (0.66–0.84) mg/mL, respectively. It displaced carbachol CRCs rightward with suppression of maximal response. In both tissues, pretreatment with propranolol (1 μM) caused rightward shift in inhibitory CRCs of the extract against carbachol-induced contractions. The ethyl acetate fraction was found more potent in relaxing smooth muscle contractions than the parent extract and its aqueous fraction. Discussion and conclusion: The results suggest that the spasmolytic and bronchorelaxant activities of S. imbricata are related to Ca+2 antagonistic and β-adrenergic agonistic effects, thus justifying some of the traditional uses of the plant.

It was recently reported that the hexapeptide Ac-RYYRIK-ol binds with high affinity nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptors and competitively antagonizes N/OFQ actions in the mouse vas deferens assay. Here we further describe the in vitro and in vivo pharmacological features of this NOP receptor ligand. In mouse brain homogenate the degradation half life of Ac-RYYRIK-ol (2.48 min) was significantly higher than that of the parent compound Ac-RYYRIK-NH 2 (1.20 min). In the electrically stimulated mouse vas deferens, Ac-RYYRIK-ol (10–1000 nM) competitively antagonized the inhibitory effect of N/OFQ (pA 2 = 8.46), while in the isolated mouse colon the hexapeptide mimicked N/OFQ contractile effects thus behaving as a NOP receptor agonist (pEC 50 = 9.09). This latter effect was no longer evident in colon tissues taken from mice knock out for the NOP receptor gene (NOP −/− ). In vivo in mice, similarly to N/OFQ, Ac-RYYRIK-ol (dose range 0.001–1 nmol) produced: i) pronociceptive effects after intracerebroventricular (i.c.v.) administration and antinociceptive actions when given intrathecally (i.t.) in the tail withdrawal assay; ii) inhibition of locomotor activity and iii) stimulation of food intake after supraspinal administration. Finally, in the forced swimming test, Ac-RYYRIK-ol was inactive per se, but reversed the antidepressant-like effects elicited by the NOP receptor selective antagonist UFP-101 ([Nphe 1 ,Arg 14 ,Lys 15 ]N/OFQ-NH 2 ). Thus, in all these in vivo assays Ac-RYYRIK-ol mimicked the actions of N/OFQ showing however higher potency. In conclusion, Ac-RYYRIK-ol displayed a complex pharmacological profile which is likely due to the low efficacy agonist nature of this novel ligand of the NOP receptor. The high potency, selectivity of action, and in vivo effectiveness make Ac-RYYRIK-ol a useful pharmacological tool for future studies in the field of N/OFQ and its NOP receptor.