Injection Of Salicylate Research Articles

Beneficial effect of metformin on tolerance to analgesic effects of sodium salicylate in male rats.

Tolerance to the analgesic effects of opioids and non-steroidal anti-inflammatory drugs (NSAIDs) is a major concern for relieving pain. Thus, it is highly valuable to find new pharmacological strategies for prolonged therapeutic procedures. Biguanide-type drugs such as metformin (MET) are effective for neuroprotection and can be beneficial for addressing opioid tolerance in the treatment of chronic pain. It has been proposed that analgesic tolerance to NSAIDs is mediated by the endogenous opioid system. According to the cross-tolerance between NSAIDs, especially sodium salicylate (SS), and opiates, especially morphine, the objective of this study was to investigate whether MET administration can reduce tolerance to the anti-nociceptive effects of SS. Fifty-six male Wistar rats were used in this research (weight 200-250 g). For induction of tolerance, SS (300 mg/kg) was injected intraperitoneally for 7 days. During the examination period, animals received MET at doses of 50, 75, or 100 mg/kg for 7 days to evaluate the development of tolerance to the analgesic effect of SS. The hot plate test was used to evaluate the drugs' anti-nociceptive properties. Salicylate injection significantly increased hot plate latency as compared to the control group, but the total analgesic effect of co-treatment with SS + Met50 was stronger than the SS group. Furthermore, the effect of this combination undergoes less analgesic tolerance over time. It can be concluded that MET can reduce the analgesic tolerance that is induced by repeated intraperitoneal injections of SS in Wister rats.

Effectiveness of transcutaneous vagus nerve stimulation (tVNS) on salicylate-induced tinnitus

IntroductionTinnitus is the most common symptom of auditory system disorders. It affects the quality of life of millions of people, but it is still incurable in most cases. Vagus nerve stimulation (VNS) therapy is a potential new treatment for subjective tinnitus. In this study, transcutaneous vagus nerve stimulation (tVNS) combined with tones was utilized to treat salicylate-induced tinnitus since salicylate is a reliable and convenient approach for rapidly inducing tinnitus. MethodsWistar rats were divided into acoustic stimulation alone (AS, n = 6), tVNS alone (n = 6), and tVNS with AS (n = 6) groups for behavioral and electrophysiological tests. They were assessed by auditory brainstem response (ABR), prepulse inhibition (PPI), gap prepulse inhibition of the acoustic startle (GPIAS), social interactions, and aggressive behavior tests at baseline and seven days’ post-salicylate (175 mg/kg, twice a day) injection. ResultsThe inhibition percentage of the GPIAS test was significantly reduced post-salicylate injection in the tVNS and AS alone groups, while it was not significant in the tVNS with AS group. There was no significant difference in the mean percentage of the GPIAS test between the tVNS groups (with or without AS) after salicylate injections. Social interactions were significantly different in the AS alone group pre- and post-salicylate injections, but they were not significant in other groups. Moreover, the results of aggressive behavior tests showed significantly increased post-salicylate injections in the AS alone group, while they were not significant in the tVNS groups (with or without AS). ConclusionsThe current study revealed that the application of tVNS alone produced improved social interaction and mood and alleviated salicylate-induced tinnitus severity. Moreover, combining tVNS with acoustic stimulation can prevent salicylate-induced tinnitus.

Anti –Inflammatory Effect of Methanolic and Aqueous Extracts of Urtica pilulifera L. Seed in Rats

Wide range of acute and chronic inflammatory ailments, side effects of their available therapies and incomplete treatment of such patients push the researches to find new and more effective drugs. To reach this aim, in the current study, we evaluate Urtica pilulifera L. (family Urticaceae) as an introduced traditional herb for treatment of inflammation in Persian Medicine (PM). In an animal study, Anti-inflammatory effects of U. pilulifera were assessed in formalin-induced hind paw edema in rats. Sodium salicylate (300 mg/kg, i.p., SS) injection was used as a positive control drug and compared with methanolic extract of U. pilulifera (20 mg/kg; i.p.) (MUP), three different doses of aqueous extract of U. pilulifera (20, 40 and 80 mg/kg; i.p.) (AUP) and a group of distilled water (6 mL/kg; i.p.). As acute anti-inflammatory effect, AUP in doses 40 and 80 mg/kg decreased edema significantly (p<0.05). In chronic anti-inflammatory response, results indicated that all AUP doses had anti-inflammatory effects (p <0.05) with no significant difference with SS group. In conclusion, AUP had anti-inflammatory effects on both acute and chronic edema; while MUP was only effective in chronic inflammation.

Susceptibility and mechanism of sodium salicylate-induced tinnitus model in low estrogen rats

Objective: The susceptibility of tinnitus rats with low estrogen level induced by sodium salicylate and the changes of tumor necrosis factor α (TNF-α) in serum were observed to investigate the relationship between tinnitus occurrence and estrogen level. Methods: Forty-two healthy female Wistar rats were randomly divided into control group(n=6), normal group(n=6), sham operation group(n=6) and ovariectomized group(n=24). Control group was intraperitoneally injected with normal saline 200 mg/kg for 14 consecutive days. Normal group, sham operation group and ovariectomized group were intraperitoneally injected with sodium salicylate 200 mg/kg for 14 consecutive days. Before and after sodium salicylate induction, the tinnitus behavior of rats in each group was detected by prepulse inhibition (PPI) and gap pre-pulse inhibition of the acoustic startle (GPIAS) test. Before and after sodium salicylate induction, blood samples were collected from eyeballs of rats in each group, and serum levels of estradiol and TNF-α were detected by ELISA. SPSS 25.0 software was used to analyze the data. Results: (1) Following 14 days of sodium salicylate intervention, there was no significant difference in PPI inhibition rate between groups or within groups(all P>0.05). (2)There was no significant difference in the inhibition rate of GPIAS in the four groups before sodium salicylate injection(F=0.217, P>0.05). With sodium salicylate injected for 14 days, the inhibition rate of GPIAS in ovariectomized group (30.88%±15.40%) was significantly lower than that in the other three groups (44.11%±21.06%, 38.27%±10.92%, 51.59%±11.34%), and the difference was statistically significant(F=3.533, P<0.05). The inhibition rate of GPIAS in ovariectomized group with sodium salicylate injected for 14 days was significantly lower than that before injection, and the difference was statistically significant(t=2.977, P<0.05).There was no significant difference in GPIAS inhibition rate between the other three groups before and after sodium salicylate injection(P>0.05). (3)The level of TNF-α in ovariectomized rats was significantly higher than that in the other three groups, the difference was statistically significant(all P<0.05). With sodium salicylate injection for 14 days, TNF-α level in the ovariectomized group increased more significantly than that in the other three groups, the difference was statistically significant(F=8.045, P<0.05). TNF-α levels increased following salicylate injection in normal group, sham operation group and ovariectomized group, and the differences were statistically significant(t value was -4.843, -4.932 and -5.965 respectively, each P<0.05). There was no significant difference in TNF-α levels before and after normal saline injection in control group(all P>0.05). Conclusion: Low estrogen levels increase susceptibility to sodium salicylate-induced tinnitus. Decreased estrogen levels may increase susceptibility to tinnitus through the increased expression of pro-inflammatory factor TNF-α.

Behavioral and Immunohistochemical Evidence for Suppressive Effects of Goshajinkigan on Salicylate-Induced Tinnitus in Rats.

Many people are affected by tinnitus, a sensation of ringing in the ear despite the absence of external sound. Goshajinkigan (GJG) is one of the formulations of Japanese traditional herbal medicine and is prescribed for the palliative treatment of patients with tinnitus. Although GJG is clinically effective in these patients, its behavioral effects and the underlying neuroanatomical substrate have not been modeled in animals. We modeled tinnitus using salicylate-treated rats, demonstrated the effectiveness of GJG on tinnitus, and examined the underlying neuronal substrate with c-Fos expression. Intraperitoneal injection of sodium salicylate (400 mg/kg) into rats for three consecutive days significantly increased false positive scores, which were used to assess tinnitus behavior. When GJG was orally administered one hour after each salicylate injection, the increase in tinnitus behavior was suppressed. The analysis of c-Fos expression in auditory-related brain areas revealed that GJG significantly reduced the salicylate-induced increase in the number of c-Fos-expressing cells in the auditory cortices, inferior colliculus, and dorsal cochlear nucleus. These results suggest a suppressive effect of GJG on salicylate-induced tinnitus in animal models.

Analysis of efficacy and safety of linezolid-based chemotherapeutic regimens for patients with postoperative multidrug-resistant spinal tuberculosis

ObjectivesThe study aimed to explore the efficacy and safety of linezolid-based chemotherapeutic regimens for patients with postoperative multidrug-resistant spinal tuberculosis. MethodsThe randomized controlled study included 50 Mycobacterium tuberculosis culture or pathological-confirmed multidrug resistant tuberculosis patients who received spinal surgery from January 2018 to February 2020. Twenty-five patients were assigned to the control group and the study group, respectively. Random number method was used for patient allocation and they were treated with levofloxacin, pyrazinamide, thioisonicotinamide enteric-coated tablet, amikacin sulfate injection, and sodium p-amino salicylate injection, accompanied by linezolid or not. ResultsThe overall effective rate of the study group was higher than that of the control group (88.00% vs 64.00%, P<0.05). The severity of pain at 3 and 6 months postoperatively was lower in the study group than that in the control group (P<0.05). Postoperatively, the study group had higher bone graft fusion rate, shorter mean bone graft fusion time, and higher paraspinal cyst absorption rate than the control group (P<0.05). Postoperatively, the study group had lower levels of PCT, ESR, and CRP than the control group (P <0.05). All patients had normal hepatic and renal function, and no statistical difference of adverse effects between 2 groups were found. ConclusionsLinezolid-based chemotherapeutic regimens can effectively treat patients with postoperative multidrug-resistant spinal tuberculosis but have higher rates of adverse reactions.

Salicylate-Induced Changes in Hearing Thresholds in Mongolian Gerbils Are Correlated With Tinnitus Frequency but Not With Tinnitus Strength.

Tinnitus is an auditory phantom percept without external sound sources. Despite the high prevalence and tinnitus-associated distress of affected patients, the pathophysiology of tinnitus remains largely unknown, making prevention and treatments difficult to develop. In order to elucidate the pathophysiology of tinnitus, animal models are used where tinnitus is induced either permanently by noise trauma or transiently by the application of salicylate. In a model of trauma-induced tinnitus, we have suggested a central origin of tinnitus-related development of neuronal hyperactivity based on stochastic resonance (SR). SR refers to the physiological phenomenon that weak subthreshold signals for given sensors (or synapses) can still be detected and transmitted if appropriate noise is added to the input of the sensor. The main objective of this study was to characterize the neurophysiological and behavioral effects during salicylate-induced tinnitus and compare these to the conditions within the trauma model. Our data show, in line with the pharmacokinetics, that hearing thresholds generally increase 2 h after salicylate injections. This increase was significantly stronger within the region of best hearing compared to other frequencies. Furthermore, animals showed behavioral signs of tinnitus during that time window and frequency range as assessed by gap prepulse inhibition of the acoustic startle reflex (GPIAS). In contrast to animals with noise trauma-induced tinnitus, salicylate-induced tinnitus animals showed no correlation between hearing thresholds and behavioral signs of tinnitus, indicating that the development of tinnitus after salicylate injection is not based on SR as proposed for the trauma model. In other words, salicylate-induced tinnitus and noise trauma-induced tinnitus are not based on the same neurophysiological mechanism.

The increase in the degree of neural forward masking of cochlea following salicylate application

BackgroundHigh doses of salicylate are known to reduce cochlear response amplitude and raise threshold. However, its effect on the cochlear forward masking, reflecting temporal resolution, is still unclear. MethodsThe neural forward masking of cochlea was evaluated using double-tone stimulation. The first tone burst (5ms) was named the “masker” and the second tone burst (5 ms) was named the “probe”. The frequency and intensity of the masker and probe were equal, and the masker-probe interval varied from 2 to 32 ms. The reduction (%) of the probe-evoked cochlear compound action potential caused by the addition of the masker tone was used to represent cochlear forward masking. The data obtained before and 2 h following the injection of sodium salicylate (250 mg/kg) were compared. ResultsThe neural forward masking of cochlea in the normal rats increased as the masker-probe interval decreased. At 16 kHz, for example, it increased from ~5% to 32ms masker-probe interval to ~85% at 2ms masker-probe interval. Two hours post salicylate injection, the neural forward masking was significantly enhanced except at 32 ms masker-probe interval. Interestingly, this enhancement was only observed in the limited frequency range of 16–30 kHz. DiscussionThe enhancement of forward masking of cochlea following salicylate administration may reflect defective neurotransmitter release. This frequency-dependent injury in the cochlea may lead to the development of central plasticity observed after salicylate administration, likely through the increase in central gain, leading to perceptual consequences.

Anxiety-like behavior induced by salicylate depends on age and can be prevented by a single dose of 5-MeO-DMT

Salicylate intoxication is a cause of tinnitus and comorbidly associated with anxiety in humans. In a previous work, we showed that salicylate induces anxiety-like behavior and hippocampal type 2 theta oscillations (theta2) in mice. Here we investigate if the anxiogenic effect of salicylate is dependent on age and previous tinnitus experience. We also tested whether a single dose of DMT can prevent this effect. Using microwire electrode arrays, we recorded local field potential in young (4–5- month-old) and old (11–13-month-old) mice to study the electrophysiological effect of tinnitus in the ventral hippocampus (vHipp) and medial prefrontal cortex (mPFC) in an open field arena and elevated plus maze 1h after salicylate (300mg/kg) injection. We found that anxiety-like behavior and increase in theta2 oscillations (4–6 Hz), following salicylate pre-treatment, only occurs in young (normal hearing) mice. We also show that theta2 and slow gamma oscillations increase in the vHipp and mPFC in a complementary manner during anxiety tests in the presence of salicylate. Finally, we show that pre-treating mice with a single dose of the hallucinogenic 5-MeO-DMT prevents anxiety-like behavior and the increase in theta2 and slow gamma oscillations after salicylate injection in normal hearing young mice. This work further support the hypothesis that anxiety-like behavior after salicylate injection is triggered by tinnitus and require normal hearing. Moreover, our results show that hallucinogenic compounds can be effective in treating tinnitus-related anxiety.

Salicylate increased ascorbic acid levels and neuronal activity in the rat auditory cortex.

ImportanceClinical observations have implied a central origin for tinnitus and potential therapeutic effects of ascorbic acid (AA); however, the detailed mechanisms remain undetermined.ObjectiveTo investigate changes in the AA levels and neural activity in the auditory cortex (AC) during salicylate‐induced tinnitus.MethodsRats were randomly divided into 3 groups: (1) saline group, which received an intraperitoneal saline injection; (2) SS group, which received an intraperitoneal sodium salicylate (SS) injection (350 mg/kg); and (3) SS+Lido group, which received an intraperitoneal SS injection (350 mg/kg) and lidocaine delivered to the AC by microdialysis. For each group, we firstly used an in vivo microdialysis technique to investigate the concentrations of AA in the AC; and secondly, we recorded the neural activity in the AC using a single‐unit recording technique.ResultsThe AA concentration in the SS group significantly increased after SS injection, whereas that of the saline group did not change. The AA concentration in the SS+Lido group also showed an increasing trend but was significantly lower than that in the SS group. In the electrophysiological study, the spontaneous firing rate of the SS group was significantly higher than that of the saline group. In addition, the proportion of short interval discharges was also higher in the SS group than in the saline group. Both differences were reversed by lidocaine treatment.InterpretationOur data suggest that the elevation of AA levels in the AC may be related to increased neuronal activity, which may represent the mechanism underlying salicylate‐induced tinnitus.

Effect of electrical stimulation at auricular points combined with sound masking on the expression of CREB, BDNF and TrkB in the auditory cortex of tinnitus rats

To explore the effect of electrical stimulation at auricular points (EAS) combined with sound masking on the expression of cAMP-response element binding protein (CREB), brain-derived neurotrophic factor (BDNF) and tyrosine receptor kinase B (TrkB) in the auditory cortex of tinnitus rats. A total of 27 adult male SD rats were randomly divided into a control group, a model group and an EAS group. The rats in the model group and the EAS group were intervened with intraperitoneal injection of sodium salicylate to induce tinnitus model, while the rats in the control group were intervened with injection of 0.9% NaCl solution. After the model was successfully established, the rats in the EAS group were treated with electrical stimulation at "Shenmen" (TF4) and "Yidan" (CO11), combined with sound masking; the treatment was given once a day for 15 days. The gap prepulse inhibition of acoustic startle (GPIAS) and prepulse inhibition (PPI) testing were performed using the acoustic startle reflex starter package for rats. The expression of BDNF, TrkB, CREB and p-CREB in the auditory cortex of each group were measured with Western Blot analysis. ① Compared with the control group, the GPIAS values in 12 kHz, 16 kHz, 20 kHz and 28 kHz were significantly decreased in the model group (all P<0.05); compared with the model group, GPIAS values in 12 kHz, 16 kHz, 20 kHz and 28 kHz were significantly increased in the EAS group (all P<0.05). ② Compared with the control group, the expression of BDNF and p-CREB in the model group was significantly increased (P<0.01), and the expression of TrkB in the model group was significantly increased (P<0.05); the differences of expression of BDNF, TrkB, CREB and p-CREB between the model group and the EAS group had no statistics significance (all P>0.05). EAS could improve the GPIAS values of high-frequency background sound in tinnitus rats, which may be related with the upregulation of the BDNF/TrkB/CREB signaling pathway in the auditory cortex, leading to the reversion of the maladaptive plasticity.

Neuroprotective effects of MK-801 on auditory cortex in salicylate-induced tinnitus: Involvement of neural activity, glutamate and ascorbate

Tinnitus may cause anxiety, depression, insomnia, which impair the quality of life of millions worldwide. However, the mechanism of tinnitus remains to be understood, it has been previously hypothesized that the activation of N-methyl-D-aspartate (NMDA) receptor is involved in the tinnitus processes and blockade of the NMDA receptor is regarded as a therapeutic strategy for tinnitus treatment even if the rescue treatment is still proved invalid in some cases. To demonstrate the therapeutic effect of the NMDA receptor blocker on tinnitus, we examined here the spontaneous firing rate (SFR) and the neurochemical dynamics in the auditory cortex (AC) of rats after sodium salicylate (SS) injection, which is a widely used model for tinnitus research. We also recorded their responses to MK-801 treatment. Electrophysiological studies showed that MK-801 significantly suppresses SFR in AC of rats with SS-induced tinnitus. In addition, by using a technique that combining in vivo microdialysis with an online electrochemical system (OECS) and a high-performance liquid chromatography (HPLC), we found that the levels of both glutamate and ascorbate in AC dramatically increased after SS injection and that MK-801 administration attenuated those response. Further studies found that MK-801 given at a time point of 30 min pre- or post-injection of SS were more effective than that given at a time point of 60 min post-SS injection, indicating that the time point of MK-801 intervention has a critical impact on the therapeutic effect. These findings suggest that MK-801 plays a neuroprotective role against hyperactivity during tinnitus induced by SS and that the therapeutic effect depends on the time point of MK-801 intervention, which would advance the studies on understanding of the therapeutic potential of NMDA receptor antagonist in tinnitus therapy.

Salicylate induces anxiety‐like behavior and slow theta oscillation and abolishes the relationship between running speed and fast theta oscillation frequency

Salicylate intoxication is a cause of tinnitus in humans and it is often used to produce tinnitus-like perception in animal models. Here, we assess whether salicylate induces anxiety-like electrophysiological and behavioral signs. Using microwire electrode arrays, we recorded local field potential in the ventral and, in some experiments dorsal hippocampus, in an open field arena 1 hr after salicylate (300 mg/kg) injection. We found that animals treated with salicylate moved dramatically less than saline treated animals. Salicylate-treated animals showed a strong 4-6 Hz (type 2) oscillation in the ventral hippocampus (with smaller peaks in dorsal hippocampus electrodes). Coherence in the 4-6 Hz-theta band was low in the ventral and dorsal hippocampus when compared to movement-related theta coherence (7-10 Hz). Moreover, movement related theta oscillation frequency decreased and its dependency on running speed was abolished. Our results suggest that salicylate-induced theta is mostly restricted to the ventral hippocampus. Slow theta has been classically associated to anxiety-like behaviors. Here, we show that salicylate application can consistently generate low frequency theta in the ventral hippocampus. Tinnitus and anxiety show strong comorbidity and the increase in ventral hippocampus low frequency theta could be part of this association.

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 limbic 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 of tinnitus 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 CA1 area was recorded with in vivo multichannel recording technology to assess changes in excitability induced by SA. To investigate the effect of excitability changes of hippocampus 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 CA1 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.

Observation of Lidocaine‐suppressed Decrease of Magnesium in Salicylate‐induced Tinnitus with an Online Electrochemical System

AbstractTinnitus, characterized by an auditory perception in the absence of actual sound, is one of the most common encountered difficulties to manage otological problems, in which, lidocaine has been shown to provide temporary relief from subjective tinnitus. However, the pathophysiological mechanism of lidocaine treatment remains to be understood. The study demonstrates the first observation on that lidocaine well suppresses the decrease in the level magnesium (Mg2+) in inferior colliculus (IC) of guinea pigs following salicylate‐induced tinnitus with an online electrochemical system (OECS) for continuously monitoring of microdialysate of Mg2+. The OECS was established by efficiently coupling a selective electrochemical detector with in vivo microdialysis to monitor Mg2+ in the microdialysate continuously sampled from animal brain. The selective detection of Mg2+ over other coexisting neurochemicals was successfully achieved through a mechanism with divalent metal cations (e. g., Mg2+, Ca2+) enhanced catalytic current of organic dyes (i. e., polymerized film of toluidine blue O, p‐TBO) toward the oxidation of nicotinamide adenine dinucleotide (NADH) and with ethyleneglcol‐bis (2‐aminoethylether) tetraacetic acid (EGTA) as selective masking agents for Ca2+. Tinnitus was induced by intraperitoneal injection of sodium salicylate (350 mg/kg body weight). For the lidocaine group, using the microdialysis probe, 1 % lidocaine was perfused into IC of guinea pigs at 2 μL/min for 20 min. With the OECS, we found that the perfusion of lidocaine could recover the decrease of the Mg2+ level caused by salicylate‐induced tinnitus. The basal level of microdialysate Mg2+ in IC of guinea pigs was previously determined to be 1.29±0.44 mM, which was decreased significantly following salicylate‐induced tinnitus. The lidocaine perfusion significantly recovers the Mg2+ level by 37.7±14.8 %. This observation suggests that Mg2+ plays an important role in the pathological mechanism of tinnitus.

Up-regulation of Ca2+/CaMKII/CREB signaling in salicylate-induced tinnitus in rats.

The purpose of the study was to investigate the changes of Ca2+/calmodulin-dependent protein kinases II (CaMKII)/cAMP response element-binding protein (CREB) signaling pathway in a rat tinnitus model. Eighteen Wistar rats were randomly divided into three groups: normal control (NC), normal saline (NS), and tinnitus model (TM) groups. Tinnitus model was induced by intraperitoneal injection of salicylate. The concentration of intracellular calcium level in auditory cortex cells was determined using Fura-2 acetoxymethyl ester (Fura-2 AM) method with fluorospectrophotometer. Expressions of calmodulin (CaM), N-methyl-D-aspartate receptor 2B subunit (NR2B), calcium-calmodulin kinase II (CaMKII), and cAMP response element-binding protein (CREB) were detected with Western blot. Tinnitus model was successfully established by the intraperitoneal administration of salicylate in rats. Compared with rats in NC and NS groups, salicylate administration significantly elevated CaM, NR2B, phospho-CaMKII and phospho-CREB expression in auditory cortex from tinnitus model group (p < 0.05), and the free intracellular Ca2+ concentrations (p < 0.05). Our data reveal that salicylate administration causes tinnitus symptoms and elevates Ca2+/CaMKII/CREB signaling pathway in auditory cortex cells. Our study likely provides a new understanding of the development of tinnitus.

Effects of Spirulina on GABA Receptor Gene Expression in Salicylate-Induced Tinnitus.

The function of γ-amino butyric acid receptor (GR) was related with tinnitus. But, the effects of Spirulina platensis water extract (SP) on the mRNA expression of GRAβ3 in mice with tinnitus were still unclear. Eighteen SAMP8 mice were divided into the control group (intraperitoneal injection of saline, once per day), the tinnitus group (intraperitoneal injection of salicylate, 300 mg/kg body weight once per day), and the spirulina group [intraperitoneal injection of salicylate, 300 mg/kg body weight and oral SP supplementation (1000 mg/kg body weight) once per day]. Effects of SP on the mRNA expression of GRAβ3 in the cochlea and brain of mice were studied for 4 days. Compared to the control group, the tinnitus group had significantly higher tinnitus scores and lower mRNA expression of GRAβ3 gene in the cochlear, brainstem, hippocampus and parahippocampus, temporal lobes, and the frontal lobes. On the other hand, the spirulina group had significantly lower tinnitus scores and higher GRAβ3 gene expression than the tinnitus group in all tested areas. SP could reduce salicylate-induced tinnitus possibly via increasing the salicylate-induced down-regulation of GRAβ3 gene expression.

Expression of Dopamine Receptor 1A and Cannabinoid Receptor 1 Genes in the Cochlea and Brain after Salicylate-Induced Tinnitus

The purpose of this study was to investigate the mRNA expression of the dopamine receptor 1A (DR1A) and cannabinoid receptor 1 (CR1) genes in mice with tinnitus. Sixteen 3-month-old male SAMP8 mice were randomly and equally divided into two groups (8 mice in each group): a control (saline-treated) group and a tinnitus (salicylate-treated) group. The mRNA expression of the DR1A and CR1 genes in the cochleae and brains of the mice was evaluated after tinnitus had been induced by intraperitoneal injection of sodium salicylate (300 mg/kg body weight). The results showed that 4-day salicylate treatment (unlike 4-day saline treatment) caused a significant increase in the tinnitus score and in mRNA expression of the DR1A gene in the cochlea, the brainstem and inferior colliculus, the hippocampus and parahippocampus, and the temporal lobe, but not the frontal lobe. Conversely, 4-day salicylate treatment caused significantly lower mRNA expression of the CR1 gene in the cochlea and all the brain areas tested. In summary, salicylate-induced tinnitus may be associated with increased mRNA expression of the DR1A gene - but with decreased mRNA expression of the CR1 gene - in the cochlea and in many tinnitus-related brain areas.

Expressions of ion co-transporter genes in salicylate-induced tinnitus and treatment effects of spirulina.

BackgroundAlthough the activity of tinnitus-related ion co-transporter are known, their mRNA expressions has seldom been reported. We aimed to investigate the mRNA expressions of tinnitus-related ion co-transporter genes, and treatment effects of Spirulina.MethodsThe mRNA expressions of K+–Cl− co-transporter (KCC2) and Na-K-2Cl co-transporter 1 (NKCC1) genes in the cochlea and brain of mice were evaluated after tinnitus was induced by intraperitoneal injection of salicylate. The effects of spirulina water extract on these gene expressions were investigated.ResultsCompared to the control group, the tinnitus scores increased significantly, however, the salicylate-induced tinnitus could be reduced significantly by spirulina water extract. The tinnitus group had higher of borderline significance mRNA expression of KCC2 gene in the cochlear, significantly higher in the temporal lobes and in the frontal lobes. Meanwhile, compared to the tinnitus group, the spirulina group had significantly lower mRNA expression of KCC2 gene in the cochlear, temporal lobes, frontal lobes and parahippocampus/hippocampus. However, the NKCC1 mRNA expression was not significantly different between three groups in the cochlea and these brain areas.ConclusionSalicylate-induced tinnitus might be associated with increased mRNA expression of KCC2 gene, but not with mRNA expressions of NKCC1 gene in the cochlear and some tinnitus-related brain areas. Spirulina reduced the expression of KCC2 genes in salicylate-induced tinnitus.

In Vivo Determination of Reduced Thiols in Rat Cerebellum Paraflocculus Following Salicylate-Induced Tinnitus by Fluorescence

ABSTRACTThe increasing number of patients suffering from tinnitus may be explained by an imbalance in the antioxidant defense system and reactive oxygen species formation, suggesting the importance of the redox homeostasis in this condition. Endogenous biothiols play important roles in maintaining redox homeostasis. Hence, to understand the role of biothiols in the pathological process of tinnitus, this study demonstrates an in vivo method for monitoring the concentrations of biothiols in the paraflocculus of the rat cerebellum during tinnitus induced by the injection of salicylate. Resorufin-based fluorescent probe 1 was used as the selective probe with in vivo microdialysis. Probe 1 was premixed with microdialysates from the paraflocculus of the rat cerebellum and transferred into a cuvette for continuous-flow fluorescence. A linear relationship between the fluorescence and the concentrations of cysteine, homocysteine, and glutathione was from 1 to 15 µM, with detection limits of 128, 148, and 183 nM, respectively. The basal level of total reduced biothiols in the paraflocculus of the rat cerebellum microdialysate was determined to be 10.62 ± 1.34 µM based on the calibration curve for homocysteine. The injection of sodium salicylate into the animals significantly decreased the reduced biothiol concentrations in the paraflocculus of the rat cerebellum from 60 min, reaching 39.5 ± 6.20% of the basal level. In contrast, at 120, 180, and 300 min, the concentrations of reduced biothiols were 55.73 ± 9.35, 58.26 ± 9.56, and 91.69 ± 6.91% of the basal level, respectively. These results imply that the decrease in reduced biothiols in the paraflocculus of the rat cerebellum may be associated with salicylate-induced tinnitus. This study offers a new platform for in vivo monitoring of reduced biothiols in the paraflocculus of the rat cerebellum following salicylate-induced tinnitus and may be useful for the investigation of this condition.