Cortico-striatal gamma oscillations are modulated by dopamine D3 receptors in dyskinetic rats

Long-term levodopa administration can lead to the development of levodopa-induced dyskinesia.Gamma oscillations are a widely recognized hallmark of abnormal neural electrical activity in levodopa-induced dyskinesia.Currently,studies have reported increased oscillation power in cases of levodopa-induced dyskinesia.However,little is known about how the other electrophysiological parameters of gamma oscillations are altered in levodopa-induced dyskinesia.Furthermore,the role of the dopamine D3 receptor,which is implicated in levodopa-induced dyskinesia,in movement disorder-related changes in neural oscillations is unclear.We found that the cortico-striatal functional connectivity of beta oscillations was enhanced in a model of Parkinson’s disease.Furthermore,levodopa application enhanced cortical gamma oscillations in cortico-striatal projections and cortical gamma aperiodic components,as well as bidirectional primary motor cortex(M1)↔dorsolateral striatum gamma flow.Administration of PD128907(a selective dopamine D3 receptor agonist)induced dyskinesia and excessive gamma oscillations with a bidirectional M1↔dorsolateral striatum flow.However,administration of PG01037(a selective dopamine D3 receptor antagonist)attenuated dyskinesia,suppressed gamma oscillations and cortical gamma aperiodic components,and decreased gamma causality in the M1→dorsolateral striatum direction.These findings suggest that the dopamine D3 receptor plays a role in dyskinesia-related oscillatory activity,and that it has potential as a therapeutic target for levodopa-induced dyskinesia.

Targeting galectin-3 to counteract spike-phase uncoupling of fast-spiking interneurons to gamma oscillations in Alzheimer’s disease

Background Alzheimer’s disease(AD)is a progressive multifaceted neurodegenerative disorder for which no disease-modifying treatment exists.Neuroinflammation is central to the pathology progression,with evidence suggesting that microglia-released galectin-3(gal3)plays a pivotal role by amplifying neuroinflammation in AD.However,the possible involvement of gal3 in the disruption of neuronal network oscillations typical of AD remains unknown.Methods Here,we investigated the functional implications of gal3 signaling on experimentally induced gamma oscillations ex vivo(20-80 Hz)by performing electrophysiological recordings in the hippocampal CA3 area of wild-type(WT)mice and of the 5×FAD mouse model of AD.In addition,the recorded slices from WT mice under acute gal3 application were analyzed with RT-qPCR to detect expression of some neuroinflammation-related genes,and amyloid-β(Aβ)plaque load was quantified by immunostaining in the CA3 area of 6-month-old 5×FAD mice with or without Gal3 knockout(KO).Results Gal3 application decreased gamma oscillation power and rhythmicity in an activity-dependent manner,which was accompanied by impairment of cellular dynamics in fast-spiking interneurons(FSNs)and pyramidal cells.We found that the gal3-induced disruption was mediated by the gal3 carbohydrate-recognition domain and prevented by the gal3 inhibitor TD139,which also prevented Aβ42-induced degradation of gamma oscillations.Further-more,the 5×FAD mice lacking gal3(5×FAD-Gal3KO)exhibited WT-like gamma network dynamics and decreased Aβplaque load.Conclusions We report for the first time that gal3 impairs neuronal network dynamics by spike-phase uncoupling of FSNs,inducing a network performance collapse.Moreover,our findings suggest gal3 inhibition as a potential therapeutic strategy to counteract the neuronal network instability typical of AD and other neurological disorders encompassing neuroinflammation and cognitive decline.

Morphological disruption and visual tuning alterations in the primary visual cortex in glaucoma(DBA/2J)mice

Glaucoma is a leading cause of irreve rsible blindness wo rldwide,and previous studies have shown that,in addition to affecting the eyes,it also causes abnormalities in the brain.However,it is not yet clear how the primary visual cortex(V1)is altered in glaucoma.This study used DBA/2J mice as a model for spontaneous secondary glaucoma.The aim of the study was to compare the electrophysiological and histomorphological chara cteristics of neurons in the V1between 9-month-old DBA/2J mice and age-matched C57BL/6J mice.We conducted single-unit recordings in the V1 of light-anesthetized mice to measure the visually induced responses,including single-unit spiking and gamma band oscillations.The morphology of layerⅡ/Ⅲneurons was determined by neuronal nuclear antigen staining and Nissl staining of brain tissue sections.Eighty-seven neurons from eight DBA/2J mice and eighty-one neurons from eight C57BL/6J mice were examined.Compared with the C57BL/6J group,V1 neurons in the DBA/2J group exhibited weaker visual tuning and impaired spatial summation.Moreove r,fewer neuro ns were observed in the V1 of DBA/2J mice compared with C57BL/6J mice.These findings suggest that DBA/2J mice have fewer neurons in the VI compared with C57BL/6J mice,and that these neurons have impaired visual tuning.Our findings provide a better understanding of the pathological changes that occur in V1 neuron function and morphology in the DBA/2J mouse model.This study might offer some innovative perspectives regarding the treatment of glaucoma.

Effects of Ketamine on Basal Gamma Band Oscillation and Sensory Gating in Prefrontal Cortex of Awake Rats

Gamma band oscillation（GBO） and sensory gating（SG） are associated with many cognitive functions.Ketamine induces deficits of GBO and SG in the prefrontal cortex（PFC）. However, the time-courses of the effects of different doses of ketamine on GBO power and SG are poorly understood. Studies have indicated that GBO power and SG have a common substrate for their generation and abnormalities. In this study, we found that（1） ketamine administration increased GBO power in the PFC in rats differently in the low-and high-dose groups;（2） auditory SG was significantly lower than baseline in the 30 mg/kg and 60 mg/kg groups, but not in the 15 mg/kg and 120 mg/kg groups; and（3） changes in SG and basal GBO power were significantly correlated in awake rats. These results indicate a relationship between mechanisms underlying auditory SG and GBO power.

Effects of transcranial ultrasound stimulation pulsed at 40 Hz on Aβplaques and brain rhythms in 5×FAD mice

Background:Alzheimer's disease(AD)is the most common cause of dementia,and is characterized by amyloid-β(Aβ)plaques and tauopathy.Reducing Aβhas been considered a major AD treatment strategy in pharmacological and non-pharmacological approaches.Impairment of gamma oscillations,which play an important role in perception and cognitive function,has been shown in mouse AD models and human patients.Recently,the therapeutic effect of gamma entrainment in AD mouse models has been reported.Given that ultrasound is an emerging neuromodulation modality,we investigated the effect of ultrasound stimulation pulsed at gamma frequency(40 Hz)in an AD mouse model.Methods:We implanted electroencephalogram(EEG)electrodes and a piezo-ceramic disc ultrasound transducer on the skull surface of 6-month-old 5×FAD and wild-type control mice(n=12 and 6,respectively).Six 5×FAD mice were treated with two-hour ultrasound stimulation at 40 Hz daily for two weeks,and the other six mice received sham treatment.Soluble and insoluble Aβlevels in the brain were measured by enzyme-linked immunosorbent assay.Spontaneous EEG gamma power was computed by wavelet analysis,and the brain connectivity was examined with phase-locking value and cross-frequency phase-amplitude coupling.Results:We found that the total Aβ42 levels,especially insoluble Aβ42;in the treatment group decreased in pre-and infra-limbic cortex(PIL)compared to that of the sham treatment group.A reduction in the number of Aβplaques was also observed in the hippocampus.There was no increase in microbleeding in the transcranial ultrasound stimulation(tUS)group.In addition,the length and number of microglial processes decreased in PIL and hippocampus.Encel-phalographic spontaneous gamma power was increased,and cross-frequency coupling was normalized,implying functional improvement after tUS stimulation.Conclusion:These results suggest that the transcranial ultrasound-based gamma-band entrainment technique can be an effective therapy for AD by reducing the Aβload and improving brain connectivity.