Role of the caudate-putamen nucleus in sensory gating in induced tinnitus in rats

Tinnitus can be described as the conscious perception of sound without external stimulation,and it is often accompanied by anxiety,depression,and insomnia.Current clinical treatments for tinnitus are ineffective.Although recent studies have indicated that the caudateputamen nucleus may be a sensory gating area involved in noise elimination in tinnitus,the underlying mechanisms of this disorder are yet to be determined.To investigate the potential role of the caudate-putamen nucleus in experimentally induced tinnitus,we created a rat model of tinnitus induced by intraperitoneal administration of 350 mg/kg sodium salicylate.Our results revealed that the mean spontaneous firing rate of the caudate-putamen nucleus was increased by sodium salicylate treatment,while dopamine levels were decreased.In addition,electrical stimulation of the caudate-putamen nucleus markedly reduced the spontaneous firing rate of neurons in the primary auditory cortex.These findings suggest that the caudate-putamen nucleus plays a sensory gating role in sodium salicylate-induced tinnitus.This study was approved by the Institutional Animal Care and Use Committee of Peking University Health Science Center(approval No.A2010031)on December 6,2017.

Effect of Neuronal Excitability in Hippocampal CA1 Area on Auditory Pathway in a Rat Model of Tinnitus

Background： Tinnitus is a common disorder that causes significant morbidity; however, the neurophysiological mechanism is not yet fully understood. A relationship between tinnitus and limbic system has been reported. As a significant component of the l imbic system, the hippocampus plays an important role in various pathological processes, such as emotional disturbance, decreased learning ability, and deterioration of memory. This study was aimed to explore the role of the hippocampus in the generation oftinnitus by electrophysiological technology. Methods： A tinnitus model was established in rats through intraperitoneal injection of salicylate （SA）. Subsequently, the spontaneous firing rate （SFR） of neurons in the hippocampal CAI area was recorded with in vivo multichannel recording technology to assess changes in excitability induced by SA. To investigate the effect of excitability changes ofhippocampus on the auditory pathway, the hippocampus was electrically stimulated and neural excitability in the auditory cortex （AC） was monitored. Results： Totally 65 neurons in the hippocampal CAI area were recorded, 45 from the SA group （n = 5）, and 20 from the saline group （n = 5）. Two hours after treatment, mean SFR of neurons in the hippocampal CA1 area had significantly increased from 3.06 ± 0.36 Hz to 9.18 ±1.30 Hz in the SA group （t = -4.521, P 〈 0.05）, while no significant difference was observed in the saline group （2.66 ± 0.36 Hz vs. 2.16 ± 0.36 Hz, t = 0.902, P 〉 0.05）. In the AC, 79.3% （157/198） of recorded neurons showed responses to electrical stimulation of the hippocampal CA1 area. Presumed pyramidal neurons were excited, while intermediate neurons were inhibited after electrical stimulation of the hippocampus. Conclusions： The study shows that the hippocampus is excited in SA-induced tinnitus, and stimulation of hippocampus could modulate neuronal excitability of the AC. The hippocampus is involved in tinnitus and may also have a regulatory effect on the neural center.

Partition of Initiators in Quasi-static Precipitation Polymerization of AAm/MAc

In order to investigate the partition of initiators for quasi-static precipitation polymerization of acrylamide （AAm） and methacrylic acid （MAc） in ethanol, azo-initiators were employed with various functional groups such as --COOCH3 （V- 601, dimethyl 2,2＇-azobis（isobutyrate））, --CN （V-65, 2,2＇-Azobis（2,4-diemthylvaleronitrile））, --COOH （V-501, 4,4＇-azobis（4-cyanovaleric acid）） and --NH-（VA-061, 2,2＇-azobis[2-（2-imidazolin-2-yl）propane]）, respectively. Particle size, induction time and kinetics of polymerization were investigated by the scanning electron microscopy （SEM） and gravimetry. It was observed that the polymerization parameters, such as the particle size, induction time and polymerization rate, were considerably affected by the functional groups of initiators. Besides, the monomer concentration also played important roles in the particle formation. By using V-601, the polymerization rate was strongly correlated with the total surface area of particles and the concentration of initiators. However, by using V-50 l, the polymerization rate was strongly related to WoQo, where W0 is the initial concentration of monomers and Ci,0, the initial concentration of initiators. The results indicated that the different functional groups determined the different partition types of initiators between the minimonomer droplets and the continuous phase due to the molecular interactions of initiator and monomers. V-601 was all partitioned in the continuous phase, but a part of V-65 was partitioned in the minimonomer droplets. Besides the V-501 dissolved in the continuous phase, a part of V-501 was adsorbed on the surface of minimonomer droplets. VA-061 destroyed the stability of minimonomer droplets by the formation of zwitterions with MAA.