Effect of Deep Brain Stimulation in The Ventral Tegmental Area on Neuronal Activity in Local and Remote Brain Regions in Kindled Mice.

OBJECTIVE: The mechanisms behind seizure suppression by deep brain stimulation (DBS) are not fully revealed, and the most optimal stimulus regimens and anatomical targets are yet to be determined. We investigated the modulatory effect of low-frequency DBS (L-DBS) in the ventral tegmental area (VTA) on neuronal activity in downstream and upstream brain areas in chemically kindled mice by assessing c-Fos immunoreactivity. MATERIALS AND METHODS: In this experimental study, 4-6 weeks old BL/6 male mice underwent stereotaxic implantation of a unilateral stimulating electrode in the VTA followed by pentylenetetrazole (PTZ) administration every other day until they showed stage 4 or 5 seizures following 3 consecutive PTZ injections. Animals were divided into control, sham-implanted, kindled, kindled-implanted, L-DBS, and kindled+L-DBS groups. In the L-DBS and kindled+L-DBS groups, four trains of L-DBS were delivered 5 min after the last PTZ injection. 48 hours after the last L-DBS, mice were transcardially perfused, and the brain was processed to evaluate c-Fos expression by immunohistochemistry. RESULTS: L-DBS in the VTA significantly decreased the c-Fos expressing cell numbers in several brain areas including the hippocampus, entorhinal cortex, VTA, substantia nigra pars compacta, and dorsal raphe nucleus but not in the amygdala and CA3 area of the ventral hippocampus compared to the sham group. CONCLUSION: These data suggest that the possible anticonvulsant mechanism of DBS in VTA can be through restoring the seizure-induced cellular hyperactivity to normal.

Prevalence of fatigue functional and social impairment among patients with rheumatic diseases compared to patients without: A cross-sectional comparison.

Rheumatic diseases (RD) are chronic diseases that significantly affect the lives of patients. Assessing health outcomes through a patient-reported outcome measurement information system (PROMIS) is essential for RD management. Moreover, these tend to be less favorable among individuals than among the rest of the population. This study aimed to compare PROMIS between RD patients and other patients. This cross sectional study was conducted in the year 2021. Information about patients with RD was obtained from the RD registry at King Saud University Medical City. Patients without RD were recruited from family medicine clinics. Patients were contacted electronically through WhatsApp© to complete the PROMIS surveys. We compared the individual PROMIS scores between the 2 groups using linear regression, adjusting for sex, nationality, marital status, education level, employment, family history of RD, income, and chronic comorbidities. There were 1024 individuals (512 with RD and 512 without RD). The most common RD was systemic lupus erythematosus (51.6%), followed by rheumatoid arthritis (44.3%). Individuals with RD reported significantly higher PROMIS T-scores for pain [ß = 6.2; 95% confidence interval (CI) = 4.76, 7.71] and fatigue (ß = 2.9; 95% CI = 1.37, 4.38) compared to those without RD. Moreover, RD individuals reported lower physical functioning (ß = -5.4; 95% CI = -6.50, -4.24) and social interaction (ß = -4.5; 95% CI = -5.73, -3.20). Patients with RD in Saudi Arabia, particularly those with systemic lupus erythematosus and rheumatoid arthritis, have significantly greater impairment in physical functioning and social interaction and report higher levels of fatigue and pain. Addressing and ameliorating these negative outcomes is necessary to improve quality of life.

Wireless stimulation of the subthalamic nucleus with nanoparticles modulates key monoaminergic systems similar to contemporary deep brain stimulation.

BACKGROUND: Deep brain stimulation (DBS) is commonly used to alleviate motor symptoms in several movement disorders. However, the procedure is invasive, and the technology has remained largely stagnant since its inception decades ago. Recently, we have shown that wireless nanoelectrodes may offer an alternative approach to conventional DBS. However, this method is still in its infancy, and more research is required to characterize its potential before it can be considered as an alternative to conventional DBS. OBJECTIVES: Herein, we aimed to investigate the effect of stimulation via magnetoelectric nanoelectrodes on primary neurotransmitter systems that have implications for DBS in movement disorders. METHODS: Mice were injected with either magnetoelectric nanoparticles (MENPs) or magnetostrictive nanoparticles (MSNPs, as a control) in the subthalamic nucleus (STN). Mice then underwent magnetic stimulation, and their motor behavior was assessed in the open field test. In addition, magnetic stimulation was applied before sacrifice and post-mortem brains were processed for immunohistochemistry (IHC) to assess the co-expression of c-Fos with either tyrosine hydroxylase (TH), tryptophan hydroxylase-2 (TPH2) or choline acetyltransferase (ChAT). RESULTS: Stimulated animals covered longer distances in the open field test when compared to controls. Moreover, we found a significant increase in c-Fos expression in the motor cortex (MC) and paraventricular region of the thalamus (PV-thalamus) after magnetoelectric stimulation. Stimulated animals showed fewer TPH2/c-Fos double-labeled cells in the dorsal raphe nucleus (DRN), as well as TH/c-Fos double-labeled cells in the ventral tegmental area (VTA), but not in the substantia nigra pars compacta (SNc). There was no significant difference in the number of ChAT/ c-Fos double-labeled cells in the pedunculopontine nucleus (PPN). CONCLUSIONS: Magnetoelectric DBS in mice enables selective modulation of deep brain areas and animal behavior. The measured behavioral responses are associated with changes in relevant neurotransmitter systems. These changes are somewhat similar to those observed in conventional DBS, suggesting that magnetoelectric DBS might be a suitable alternative.

The role of neurotransmitter systems in mediating deep brain stimulation effects in Parkinson's disease.

Deep brain stimulation (DBS) is among the most successful paradigms in both translational and reverse translational neuroscience. DBS has developed into a standard treatment for movement disorders such as Parkinson's disease (PD) in recent decades, however, specific mechanisms behind DBS's efficacy and side effects remain unrevealed. Several hypotheses have been proposed, including neuronal firing rate and pattern theories that emphasize the impact of DBS on local circuitry but detail distant electrophysiological readouts to a lesser extent. Furthermore, ample preclinical and clinical evidence indicates that DBS influences neurotransmitter dynamics in PD, particularly the effects of subthalamic nucleus (STN) DBS on striatal dopaminergic and glutamatergic systems; pallidum DBS on striatal dopaminergic and GABAergic systems; pedunculopontine nucleus DBS on cholinergic systems; and STN-DBS on locus coeruleus (LC) noradrenergic system. DBS has additionally been associated with mood-related side effects within brainstem serotoninergic systems in response to STN-DBS. Still, addressing the mechanisms of DBS on neurotransmitters' dynamics is commonly overlooked due to its practical difficulties in monitoring real-time changes in remote areas. Given that electrical stimulation alters neurotransmitter release in local and remote regions, it eventually exhibits changes in specific neuronal functions. Consequently, such changes lead to further modulation, synthesis, and release of neurotransmitters. This narrative review discusses the main neurotransmitter dynamics in PD and their role in mediating DBS effects from preclinical and clinical data.

High-frequency stimulation of the subthalamic nucleus induces a sustained inhibition of serotonergic system via loss of cell phenotype.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a standard treatment for Parkinson's disease (PD). However, in a considerable number of patients debilitating psychiatric side-effects occur. Recent research has revealed that external stimuli can alter the neurotransmitters' homeostasis in neurons, which is known as "neurotransmitter respecification". Herein, we addressed if neurotransmitter respecification could be a mechanism by which DBS suppresses the serotonergic function in the dorsal raphe nucleus (DRN) leading to mood changes. We infused transgenic 5-HT-Cre (ePET-Cre) mice with AAV viruses to achieve targeted expression of eYFP and the genetically encoded calcium indicator GCaMP6s in the DRN prior to methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. Mice received bilateral DBS electrodes in the STN and an optic fiber in the DRN for calcium photometry. MPTP-treated mice demonstrated behavioral and histological PD phenotype, whereas all STN-DBS animals exhibited an increased immobility time in the forced swim test, reduced calcium activity, and loss of tryptophan hydroxylase-2 expression in the DRN. Given the prominent role of calcium transients in mediating neurotransmitter respecification, these results suggest a loss of serotonergic phenotype in the DRN following STN-DBS. These findings indicate that loss of serotonergic cell phenotype may underlie the unwanted depressive symptoms following STN-DBS.

Post-Mortem Analysis of Neuropathological Changes in Human Tinnitus.

Tinnitus is the phantom perception of a sound, often accompanied by increased anxiety and depressive symptoms. Degenerative or inflammatory processes, as well as changes in monoaminergic systems, have been suggested as potential underlying mechanisms. Herein, we conducted the first post-mortem histopathological assessment to reveal detailed structural changes in tinnitus patients' auditory and non-auditory brain regions. Tissue blocks containing the medial geniculate body (MGB), thalamic reticular nucleus (TRN), central part of the inferior colliculus (CIC), and dorsal and obscurus raphe nuclei (DRN and ROb) were obtained from tinnitus patients and matched controls. Cell density and size were assessed in Nissl-stained sections. Astrocytes and microglia were assessed using immunohistochemistry. The DRN was stained using antibodies raised against phenylalanine hydroxylase-8 (PH8) and tyrosine-hydroxylase (TH) to visualize serotonergic and dopaminergic cells, respectively. Cell density in the MGB and CIC of tinnitus patients was reduced, accompanied by a reduction in the number of astrocytes in the CIC only. Quantification of cell surface size did not reveal any significant difference in any of the investigated brain regions between groups. The number of PH8-positive cells was reduced in the DRN and ROb of tinnitus patients compared to controls, while the number of TH-positive cells remained unchanged in the DRN. These findings suggest that both neurodegenerative and inflammatory processes in the MGB and CIC underlie the neuropathology of tinnitus. Moreover, the reduced number of serotonergic cell bodies in tinnitus cases points toward a potential role of the raphe serotonergic system in tinnitus.

The Effect of Noise Trauma and Deep Brain Stimulation of the Medial Geniculate Body on Tissue Activity in the Auditory Pathway.

Tinnitus is defined as the phantom perception of sound. To date, there is no curative treatment, and contemporary treatments have failed to show beneficial outcomes. Deep brain stimulation has been suggested as a potential therapy for refractory tinnitus. However, the optimal target and stimulation regimens remain to be defined. Herein, we investigated metabolic and neuronal activity changes using cytochrome C oxidase histochemistry and c-Fos immunohistochemistry in a noise trauma-induced rat model of tinnitus. We also assessed changes in neuronal activity following medial geniculate body (MGB) high-frequency stimulation (HFS). Metabolic activity was reduced in the primary auditory cortex, MGB and CA1 region of the hippocampus in noise-exposed rats. Additionally, c-Fos expression was increased in the primary auditory cortex of those animals. Furthermore, MGB-HFS enhanced c-Fos expression in the thalamic reticular nucleus. We concluded that noise trauma alters tissue activity in multiple brain areas including the auditory and limbic regions. MGB-HFS resulted in higher neuronal activity in the thalamic reticular nucleus. Given the prominent role of the auditory thalamus in tinnitus, these data provide more rationales towards targeting the MGB with HFS as a symptom management tool in tinnitus.

Deep brain stimulation of the nucleus basalis of Meynert in an experimental rat model of dementia: Stimulation parameters and mechanisms.

BACKGROUND/OBJECTIVE: Deep brain stimulation (DBS) of the nucleus basalis of Meynert (NBM) has gained interest as a potential therapy for treatment-resistant dementia. However, optimal stimulation parameters and mechanisms of action are yet to be elucidated. METHODS: First, we assessed NBM DBS at different stimulation parameters in a scopolamine-induced rat model of dementia. Rats were tested in the object location task with the following conditions: (i) low and high frequency (20 Hz or 120 Hz), (ii) monophasic or biphasic pulse shape (iii) continuous or intermittent DBS (20s on, 40s off) and 100 µA amplitude. Thereafter, rats were stimulated with the most effective parameter followed by 5-bromo-2'-deoxyuridine (BrdU) administration and perfused 4 weeks later. We then evaluated the effects of NBM DBS on hippocampal neurogenesis, synaptic plasticity, and on cholinergic fibres in the perirhinal and cingulate cortex using immunohistochemistry. We also performed in-vivo microdialysis to assess circuit-wide effects of NBM DBS on hippocampal acetylcholine levels during on and off stimulation. RESULTS: Biphasic, low frequency and intermittent NBM DBS reversed the memory impairing effects of scopolamine when compared to sham rats. We found that acute stimulation promoted proliferation in the dentate gyrus, increased synaptic plasticity in the CA1 and CA3 subregion of the hippocampus, and increased length of cholinergic fibres in the cingulate gyrus. There was no difference regarding hippocampal acetylcholine levels between the groups. CONCLUSION: These findings suggest that the potential mechanism of action of the induced memory enhancement through NBM DBS might be due to selective neuroplastic and neurochemical changes.

Clinical and demographic characteristics of patients with coronavirus disease 2019 in Security Forces Hospital, Riyadh, Saudi Arabia.

BACKGROUND: Corona virus disease (COVID-19) is a global pandemic public health problem which affected more than 5 million worldwide and caused more than 500,000 deaths. Disease presentations varied from a symptomatic or mild to severe illness which leads to death. AIM: The study describes the demographic and clinical characteristics patients with coronavirus disease 2019 (COVID-19) admitted to Security Forces Hospital in Riyadh, Saudi Arabia between 15th March till 30th of June 2020. METHODS: Study group studied a case series of 566 consecutive patients with COVID-19 evaluated at Security Forces Hospital in Riyadh, Saudi Arabia from 15th March and 30th June 2020. MAIN OUTCOMES: Demographic data, underlying co-morbidities, clinical presentation, and treatment were collected. RESULTS: Demographically, COVID-19 was more prevalent in male, Saudi, nonsmokers with blood group O + ve patients. It's more common in patients with co-morbidities like diabetes and hypertension. Fever, cough, and shortness of breath are the most common presenting symptoms. ESR, CRP, LDH, and Ferretin are the commonest laboratory abnormalities found. CONCLUSION: Totally, 556 case series patients showed more prevalence in aged male with diabetes as co-morbidity. Fever and cough are the most presenting symptoms with high inflammatory markers.

Complications of arteriovenous fistula in dialysis patients: Incidence and risk factors in Taif city, KSA.

AIM: The aim of this study was to measure the prevalence of arteriovenous fistula (AVF) and its complications in patients undergoing hemodialysis (HD) in Taif Region, Saudi Arabia. METHODS: This was a prospective hospital-based study conducted on 196 patients aged above 18 years who were undergoing dialysis in two hospital Taif City. Data collected and documented using a pretested questionnaire, which included sociodemographic details and also information about fistula-related complications. Hospital records were also reviewed to match the complication and related risk factors. Appropriate statistical tests were used and analyzed with SPSS software ver. 23. RESULTS: Majority of the study patients were in the age group of 41-60 years and the prevalence in male and female were 49.5% and 50.5%, respectively. The most prevalent chronic illness in the patients was hypertension (41.7%) and more than 30.6% had multiple chronic illness. The most common type of AVF was radiocephalic fistula (RCF). The most common complication associated with the patients with AVF was ischemic neuropathy (29.6%). Smokers had significant history of myocardial infarction than non smokers. CONCLUSION: Early and timely detection of complications in AVF is essential for proper management. Health professional should have thorough knowledge regarding the complications related to AVF. Early diagnosis and appropriate treatment are essential to improve the quality of life in patients on HD.