1,3,4‐thiadiazines as promising compounds acting on the serotonin turnover
Authors: Sarapultsev Alexey P , Chupakhin Oleg N , Vassiliev Pavel M , Tseilikman Vadim E , Dremencov Eliyahu , Sarapultsev Petr A , Ianalieva Laura , Sidorova Larisa , Grinchii Daniil , Paliokha Ruslan 
Published: June 2021

According to the previous data, 1,3,4‐thiadiazines are able to reduce the stress reaction's magnitude and acts like the atypical neuroleptics. Thus, the aim of the present study was to analyze the influence of 1,3,4‐thiadiazine compound (L‐17) on the serotonin turnover in silico and in vivo.In silico studiesThe target proteins of in silico study included the serotonin receptor type 3A (5‐HT3A) and the serotonin transporter (SERT). For the evaluation of the L‐17 compound's affinity, the docking of the compound to the specific binding sites of these proteins was performed. Experimental X‐ray 3D models were obtained from Protein Data Bank in Europe. The 3‐D model of the L‐17 compound was constructed using the molecular mechanics methods in the MarvinSketch 15.6.15 program, followed by optimization with the semi‐empirical quantum chemical method PM7 in the MOPAC2016 program. The docking was performed using AutoDockVina 1.1.2.In vivo studiesAdult male Wistar rats (200–250 g) were housed in a temperature‐controlled room with a 12:12 hours light‐dark cycle. All experimental procedures were approved by the Animal Care and Use Committee and conformed to the Directive 2010/63/EU of the European Parliament. The rats received intravenous (i.p.) injections of L‐17 (0.1–12 mg/kg) dissolved in saline. Control animals were injected saline using the same protocol. One hour after the last saline or L‐17 injection, rats were anesthetized with chloral hydrate and mounted into the stereotaxic frame. The scalp was opened and a 3 mm hole was drilled in the skull for insertion of electrodes. Serotonin neurons were identified by their typical firing rate, positive bi‐ or tri‐phasic action potential and the cumulative duration of depolarization and repolarization phases, and recorded for at least two minutes using the Power Lab data acquisition system and Lab Chart software.ResultsAccording to the results of the in silico prediction, the values of the docking energy of the L‐17 compound in the binding sites for SERT were 8.1 and 8.3 kcal/mol for 5‐HT3A and SERT, respectively. Molecular docking revealed that the moderate serotonin‐blocking effect of L‐17 was due, above all, to a sufficiently high affinity for SERT; the direct antagonism to 5‐HT3A receptors was negligible. According to the electrophysiological study results, the mean basal firing activity was 3.46±0.83 Hz. L‐17 (0.1–12 mg/kg, i.v.) significantly and dose‐dependently (Fdf 8,53=4.84, p<0.001, ANOVA for repeated measured) inhibited the firing activity of 5‐Ht neurons, reaching the maximal 90%‐ inhibition at 12 mg/kg. WAY100135 partially reversed the L17‐induced inhibition of 5‐HT neurons.Thus, the electrophysiological study confirmed the results of in silico prediction, identifying SERT as a potential biotarget of the promising compounds from the group of substituted 1,3,4‐thiadiazines.Support or Funding InformationThr study was supported by the Russian Science Foundation (project 17‐15‐01318)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.