Hypnotic Effects And Mechanisms Of Novel Modifiers Of N~6-(4-hydroxybenzyl) Adenosine Riboside:YZG-330 And YZG-331

Professor SHI Jiangong in the department of Phytochemistry isolated the N6-(4-hydroxybenzyl) adenine riboside (NHBA). We got a pair of enantiomer YZG-330/YZG331 via modifying this leading structure. My study aimed to investigate the potential sedative and hypnotic effects and possible mechanisms of them.Former results indicated that the two compounds could both affect the cellular chloride concentration. Then, in the open field experiment, YZGs inhibited the locomotor activity in a dose-dependent manner.Administrated orally at the dose of 0.125,0.5,2 mg/kg, YZG-330 decreased the total locomotor activity by 11%,48%(p<0.01),69%(p<0.001), respectively compared with vehicle within 25 min afteradministration.YZG-331 (1.25,5,20 mg/kg i.g.) decreased the total locomotor activity by 14%,46%(p<0.01),76%(p<0.001) respectively compared with vehicle. That means both of them showed sedative effect. YZG-330 is much more powerful than YZG-331.In the sleep time-prolonging test with threshold dosage pentobarbital sodium, YZGs significantly prolonged the total sleep time in mice.YZG-330 (0.125,0.5,2 mg/kg i.g.) increased the sleeping time by 25%,64% (p<0.01),500%(p<0.001), respectively in pentobarbital sodium (40 mg/kg, ip) treated mice.YZG-331 (5,10,20 mg/kg i.g.) increased the sleeping time by 70%(p<0.01), 165%(p<0.01),385%(p<0.001), respectively.Thereafter, the two compounds could let the mice which are awake from threshold dosage pentobarbital sodium induced sleeping fall asleep again. It means that YZGs have hypnotic effect.The phenomenon that intracerebroventricular (i.c.v.) infusion of YZGs could induce sleep directly means that the two compounds take their hypnotic effects in the central nervous system.EEG results showed that YZGs administered i.g. significantly shortened the sleep latency to non-rapid eye movement (NREM) sleep, increased the amount of NREM sleep, and prolonged the duration of NREM sleep episodes, in a dose dependent manner. YZG-330 hardly affected the number of bouts of wake and NREM sleep; but YZG-331 increased both of them in a dose dependent manner.YZG-330 had no affect on the number of state transitions from wakefulness to NREM sleep and subsequently from NREM sleep to wakefulness. However, YZG-331 increased the state transitions between wakefulness and NREM sleep in a dose dependent manner. Both of them decrease the number of state transitions with related to REM sleep.EEG power was increased at delta frequencies (<4Hz), the peak increase being at 1-2 Hz, and was significantly decreased at higher frequencies (>6 Hz). It means that YZGs can increase the depth of sleep. The increase of delta power desity induced by YZG-330 was much more intense than that induced by YZG-331 (222% vs 168 %).So, YZGs shortened the sleep latency, prolonged NREM sleep time, stabilized the NREM sleep and increase the depth of NREM sleep.Then I specified the receptor subtype mediated the effect of YZGs.Former results indicated that both compounds showed affinity to the adenosine receptor and functional activity by ligand-receptor binding assay (RBA),I used adenosine receptor (ADR) antagonism aminophylline, DPCPX, and SCH-58261 to antagonize the effect of YZGs. The result shows that non-selective ADR antagonism and ADR A1 antagonism could antagonize the effect of YZGs on locomotor activity. But ADR A2 receptor antagonism made nonsense to the effect of YZGs.The results of HPLC showed that YZGs decreased adenosine concentration in brainstem, thalamus, hypothalamus, diencephalon, and cortex.YZGs could increase the concentration ratio of inosine to adenosine in brainstem, hypothalamus, and diencephalon. YZGs decreased the concentration of NE and 5-HT in thalamus and diencephalon. YZGs decreased the concentration of GABA in thalamus and striatum but increased its concentration in cortex.