Cortical parvalbumin neurons are responsible for homeostatic sleep rebound through CaMKII activation.

The homeostatic regulation of sleep is characterized by rebound sleep after prolonged wakefulness, but the molecular and cellular mechanisms underlying this regulation are still unknown. In this study, we show that Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent activity control of parvalbumin (PV)-expressing cortical neurons is involved in homeostatic regulation of sleep in male mice. Prolonged wakefulness enhances cortical PV-neuron activity. Chemogenetic suppression or activation of cortical PV neurons inhibits or induces rebound sleep, implying that rebound sleep is dependent on increased activity of cortical PV neurons. Furthermore, we discovered that CaMKII kinase activity boosts the activity of cortical PV neurons, and that kinase activity is important for homeostatic sleep rebound. Here, we propose that CaMKII-dependent PV-neuron activity represents negative feedback inhibition of cortical neural excitability, which serves as the distributive cortical circuits for sleep homeostatic regulation.

Inhibition of prefrontal cortex parvalbumin interneurons mitigates behavioral and physiological sequelae of chronic stress in male mice.

Chronic stress leads to hypofunction of the medial prefrontal cortex (mPFC), mechanisms of which remain to be determined. Enhanced activation of GABAergic of parvalbumin (PV) expressing interneurons (INs) is thought to play a role in stress-induced prefrontal inhibition. In this study, we tested whether chemogenetic inhibition of mPFC PV INs after chronic stress can rescue chronic stress-related behavioral and physiological phenotypes. Mice underwent 2 weeks of chronic variable stress (CVS) followed by a battery of behavioral tests known to be affected by chronic stress exposure, e.g. an open field (OF), novel object recognition (NOR), tail suspension test (TST), sucrose preference test (SPT), and light dark (LD) box. Inhibitory DREADDs were actuated by 3 mg/kg CNO administered 30 min prior to each behavioral test. CVS caused hyperactivity in the OF, reduced sucrose preference in the SPT (indicative of enhanced anhedonia), and increased anxiety-like behavior in the LD box. Inhibition of PV IN after stress mitigated these effects. In addition, CVS also resulted in reduced thymus weight and body weight loss, which were also mitigated by PV IN inhibition. Our results indicate that chronic stress leads to plastic changes in PV INs that may be mitigated by chemogenetic inhibition. Our findings implicate cortical GABAergic INs as a therapeutic target in stress-related diseases.

Thalamic cells and pathway for social memory processing and storage.

In this issue of Neuron, Wang et al.1 demonstrate that parvalbumin interneurons in the sensory thalamic reticular nucleus are necessary and sufficient for regulating social memory in mice, identify a novel cortico-reticular thalamic-parafascicular pathway for social cognition, and highlight an essential role of GABAergic inhibitory neurons in social memory engrams.

Topographic Organization of Glutamatergic and GABAergic Parvalbumin-Positive Neurons in the Lateral Habenula.

Parvalbumin-expressing (PV) neurons, classified by their expression of the calcium-binding protein parvalbumin, play crucial roles in the function and plasticity of the lateral habenular nucleus (LHb). This study aimed to deepen our understanding of the LHb by collecting information about the heterogeneity of LHb PV neurons in mice. To achieve this, we investigated the proportions of the transmitter machinery in LHb PV neurons, including GABAergic, glutamatergic, serotonergic, cholinergic, and dopaminergic neurotransmitter markers, using transcriptome analysis, mRNA in situ hybridization chain reaction, and immunohistochemistry. LHb PV neurons comprise three subsets: glutamatergic, GABAergic, and double-positive for glutamatergic and GABAergic machinery. By comparing the percentages of the subsets, we found that the LHb was topographically organized anteroposteriorly; the GABAergic and glutamatergic PV neurons were preferentially distributed in the anterior and posterior LHb, respectively, uncovering the anteroposterior topography of the LHb. In addition, we confirmed the mediolateral topography of lateral GABAergic PV neurons. These findings suggest that PV neurons play distinct roles in different parts of the LHb along the anteroposterior and mediolateral axes, facilitating the topographic function of the LHb. It would be interesting to determine whether their topography is differentially involved in various cognitive and motivational processes associated with the LHb, particularly the involvement of posterior glutamatergic PV neurons.

PV and SST neurons in the anterior cingulate cortex regulate social disorders in adulthood induced by sensory abnormalities in childhood.

OBJECTIVE: Childhood sensory abnormalities experience has a crucial influence on the structure and function of the adult brain. The underlying mechanism of neurological function induced by childhood sensory abnormalities experience is still unclear. Our study was to investigate whether the GABAergic neurons in the anterior cingulate cortex (ACC) regulate social disorders caused by childhood sensory abnormalities experience. METHODS: We used two mouse models, complete Freund's adjuvant (CFA) injection mice and bilateral whisker trimming (BWT) mice in childhood. We applied immunofluorescence, chemogenetic and optogenetic to study the mechanism of parvalbumin (PV) neurons and somatostatin (SST) neurons in ACC in regulating social disorders induced by sensory abnormalities in childhood. RESULTS: Inflammatory pain in childhood leads to social preference disorders, while BWT in childhood leads to social novelty disorders in adult mice. Inflammatory pain and BWT in childhood caused an increase in the number of PV and SST neurons, respectively, in adult mice ACC. Inhibiting PV neurons in ACC improved social preference disorders in adult mice that experienced inflammatory pain during childhood. Inhibiting SST neurons in ACC improved social novelty disorders in adult mice that experienced BWT in childhood. CONCLUSIONS: Our study reveals that PV and SST neurons of the ACC may play a critical role in regulating social disorders induced by sensory abnormalities in childhood.

Developmental hearing loss-induced perceptual deficits are rescued by genetic restoration of cortical inhibition.

Even a transient period of hearing loss during the developmental critical period can induce long-lasting deficits in temporal and spectral perception. These perceptual deficits correlate with speech perception in humans. In gerbils, these hearing loss-induced perceptual deficits are correlated with a reduction of both ionotropic GABAA and metabotropic GABAB receptor-mediated synaptic inhibition in auditory cortex, but most research on critical period plasticity has focused on GABAA receptors. Therefore, we developed viral vectors to express proteins that would upregulate gerbil postsynaptic inhibitory receptor subunits (GABAA, Gabra1; GABAB, Gabbr1b) in pyramidal neurons, and an enzyme that mediates GABA synthesis (GAD65) presynaptically in parvalbumin-expressing interneurons. A transient period of developmental hearing loss during the auditory critical period significantly impaired perceptual performance on two auditory tasks: amplitude modulation depth detection and spectral modulation depth detection. We then tested the capacity of each vector to restore perceptual performance on these auditory tasks. While both GABA receptor vectors increased the amplitude of cortical inhibitory postsynaptic potentials, only viral expression of postsynaptic GABAB receptors improved perceptual thresholds to control levels. Similarly, presynaptic GAD65 expression improved perceptual performance on spectral modulation detection. These findings suggest that recovering performance on auditory perceptual tasks depends on GABAB receptor-dependent transmission at the auditory cortex parvalbumin to pyramidal synapse and point to potential therapeutic targets for developmental sensory disorders.

Adolescent administration of ketamine impairs excitatory synapse formation onto parvalbumin-positive GABAergic interneurons in mouse prefrontal cortex.

Ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, induces deficits in cognition and information processing following chronic abuse. Adolescent ketamine misuse represents a significant global public health issue; however, the neurodevelopmental mechanisms underlying this phenomenon remain largely elusive. This study investigated the long-term effects of sub-chronic ketamine (Ket) administration on the medial prefrontal cortex (mPFC) and associated behaviors. In this study, Ket administration during early adolescence displayed a reduced density of excitatory synapses on parvalbumin (PV) neurons persisting into adulthood. However, the synaptic development of excitatory pyramidal neurons was not affected by ketamine administration. Furthermore, the adult Ket group exhibited hyperexcitability and impaired socialization and working memory compared to the saline (Sal) administration group. These results strongly suggest that sub-chronic ketamine administration during adolescence results in functional deficits that persist into adulthood. Bioinformatic analysis indicated that the gene co-expression module1 (M1) decreased expression after ketamine exposure, which is crucial for synapse development in inhibitory neurons during adolescence. Collectively, these findings demonstrate that sub-chronic ketamine administration irreversibly impairs synaptic development, offering insights into potential new therapeutic strategies.

Persistent Interruption in Parvalbumin-Positive Inhibitory Interneurons: Biophysical and Mathematical Mechanisms.

Persistent activity in excitatory pyramidal cells (PYRs) is a putative mechanism for maintaining memory traces during working memory. We have recently demonstrated persistent interruption of firing in fast-spiking parvalbumin-expressing interneurons (PV-INs), a phenomenon that could serve as a substrate for persistent activity in PYRs through disinhibition lasting hundreds of milliseconds. Here, we find that hippocampal CA1 PV-INs exhibit type 2 excitability, like striatal and neocortical PV-INs. Modeling and mathematical analysis showed that the slowly inactivating potassium current KV1 contributes to type 2 excitability, enables the multiple firing regimes observed experimentally in PV-INs, and provides a mechanism for robust persistent interruption of firing. Using a fast/slow separation of times scales approach with the KV1 inactivation variable as a bifurcation parameter shows that the initial inhibitory stimulus stops repetitive firing by moving the membrane potential trajectory onto a coexisting stable fixed point corresponding to a nonspiking quiescent state. As KV1 inactivation decays, the trajectory follows the branch of stable fixed points until it crosses a subcritical Hopf bifurcation (HB) and then spirals out into repetitive firing. In a model describing entorhinal cortical PV-INs without KV1, interruption of firing could be achieved by taking advantage of the bistability inherent in type 2 excitability based on a subcritical HB, but the interruption was not robust to noise. Persistent interruption of firing is therefore broadly applicable to PV-INs in different brain regions but is only made robust to noise in the presence of a slow variable, KV1 inactivation.

Parvalbumin gates chronic pain through the modulation of firing patterns in inhibitory neurons.

Spinal cord dorsal horn inhibition is critical to the processing of sensory inputs, and its impairment leads to mechanical allodynia. How this decreased inhibition occurs and whether its restoration alleviates allodynic pain are poorly understood. Here, we show that a critical step in the loss of inhibitory tone is the change in the firing pattern of inhibitory parvalbumin (PV)-expressing neurons (PVNs). Our results show that PV, a calcium-binding protein, controls the firing activity of PVNs by enabling them to sustain high-frequency tonic firing patterns. Upon nerve injury, PVNs transition to adaptive firing and decrease their PV expression. Interestingly, decreased PV is necessary and sufficient for the development of mechanical allodynia and the transition of PVNs to adaptive firing. This transition of the firing pattern is due to the recruitment of calcium-activated potassium (SK) channels, and blocking them during chronic pain restores normal tonic firing and alleviates chronic pain. Our findings indicate that PV is essential for controlling the firing pattern of PVNs and for preventing allodynia. Developing approaches to manipulate these mechanisms may lead to different strategies for chronic pain relief.

Development of an indirect competitive ELISA based on the common epitope of fish parvalbumin for its detection.

A common epitope (AGSFDHKKFFKACGLSGKST) of parvalbumin from 16 fish species was excavated using bioinformatics tools combined with the characterization of fish parvalbumin binding profile of anti-single epitope antibody in this study. A competitive enzyme-linked immunosorbent assay (ELISA) based on the common epitope was established with a limit of detection of 10.15 ng/mL and a limit of quantification of 49.29 ng/mL. The developed ELISA exhibited a narrow range (71% to 107%) of related cross-reactivity of 15 fish parvalbumin. Besides, the recovery, the coefficient of variations for the intra-assay and the inter-assay were 84.3% to 108.2%, 7.4% to 13.9% and 8.5% to 15.6%. Our findings provide a novel idea for the development of a broad detection method for fish allergens and a practical tool for the detection of parvalbumin of economic fish species in food samples.

Parvalbumin-expressing basal forebrain neurons mediate learning from negative experience.

Parvalbumin (PV)-expressing GABAergic neurons of the basal forebrain (BFPVNs) were proposed to serve as a rapid and transient arousal system, yet their exact role in awake behaviors remains unclear. We performed bulk calcium measurements and electrophysiology with optogenetic tagging from the horizontal limb of the diagonal band of Broca (HDB) while male mice were performing an associative learning task. BFPVNs responded with a distinctive, phasic activation to punishment, but showed slower and delayed responses to reward and outcome-predicting stimuli. Optogenetic inhibition during punishment impaired the formation of cue-outcome associations, suggesting a causal role of BFPVNs in associative learning. BFPVNs received strong inputs from the hypothalamus, the septal complex and the median raphe region, while they synapsed on diverse cell types in key limbic structures, where they broadcasted information about aversive stimuli. We propose that the arousing effect of BFPVNs is recruited by aversive stimuli to serve crucial associative learning functions.

Inter and intralaminar excitation of parvalbumin interneurons in mouse barrel cortex.

Parvalbumin (PV) interneurons are inhibitory fast-spiking cells with essential roles in directing the flow of information through cortical circuits. These neurons set the balance between excitation and inhibition and control rhythmic activity. PV interneurons differ between cortical layers in their morphology, circuitry, and function, but how their electrophysiological properties vary has received little attention. Here we investigate responses of PV interneurons in different layers of primary somatosensory barrel cortex (BC) to different excitatory inputs. With the genetically-encoded hybrid voltage sensor, hVOS, we recorded voltage changes in many L2/3 and L4 PV interneurons simultaneously, with stimulation applied to either L2/3 or L4. A semi-automated procedure was developed to identify small regions of interest corresponding to single responsive PV interneurons. Amplitude, half-width, and rise-time were greater for PV interneurons residing in L2/3 compared to L4. Stimulation in L2/3 elicited responses in both L2/3 and L4 with longer latency compared to stimulation in L4. These differences in latency between layers could influence their windows for temporal integration. Thus, PV interneurons in different cortical layers of BC respond in a layer specific and input specific manner, and these differences have potential roles in cortical computations.

Complexin-1 enhances ultrasound neurotransmission in the mammalian auditory pathway.

Unlike megabats, which rely on well-developed vision, microbats use ultrasonic echolocation to navigate and locate prey. To study ultrasound perception, here we compared the auditory cortices of microbats and megabats by constructing reference genomes and single-nucleus atlases for four species. We found that parvalbumin (PV)+ neurons exhibited evident cross-species differences and could respond to ultrasound signals, whereas their silencing severely affected ultrasound perception in the mouse auditory cortex. Moreover, megabat PV+ neurons expressed low levels of complexins (CPLX1-CPLX4), which can facilitate neurotransmitter release, while microbat PV+ neurons highly expressed CPLX1, which improves neurotransmission efficiency. Further perturbation of Cplx1 in PV+ neurons impaired ultrasound perception in the mouse auditory cortex. In addition, CPLX1 functioned in other parts of the auditory pathway in microbats but not megabats and exhibited convergent evolution between echolocating microbats and whales. Altogether, we conclude that CPLX1 expression throughout the entire auditory pathway can enhance mammalian ultrasound neurotransmission.

Activity of ventral hippocampal parvalbumin interneurons during anxiety.

Anxiety plays a key role in guiding behavior in response to potential threats. Anxiety is mediated by the activation of pyramidal neurons in the ventral hippocampus (vH), whose activity is controlled by GABAergic inhibitory interneurons. However, how different vH interneurons might contribute to anxiety-related processes is unclear. Here, we investigate the role of vH parvalbumin (PV)-expressing interneurons while mice transition from safe to more anxiogenic compartments of the elevated plus maze (EPM). We find that vH PV interneurons increase their activity in anxiogenic EPM compartments concomitant with dynamic changes in inhibitory interactions between PV interneurons and pyramidal neurons. By optogenetically inhibiting PV interneurons, we induce an increase in the activity of vH pyramidal neurons and persistent anxiety. Collectively, our results suggest that vH inhibitory microcircuits may act as a trigger for enduring anxiety states.

Parvalbumin Gene: A Valuable Marker for Pike Authentication and Allergen Risk Assessment.

Fish from the pike (Esox) genus are valued in gastronomy for their superior meat quality. However, they can cause allergic reactions in sensitive consumers. This work aimed to fill the gap in the detection of pike allergens using molecular-biological techniques. New, fast, and accurate loop-mediated isothermal amplification (LAMP) and real-time PCR (qPCR) assays were designed to detect pike DNA using the parvalbumin gene as a marker. LAMP was assessed by electrophoresis, SYBR green optical detection, and real-time fluorescence detection. The latter was the most sensitive, detecting as little as 0.78 ng of pike DNA; the qPCR detection limit was 0.1 ng. The LAMP analysis took 20-70 min, which is significantly faster than qPCR. The study provides reliable detection and quantification of the parvalbumin gene in both fresh and processed samples and further highlights the versatility of the use of the parvalbumin gene for the authentication of food products and consumer protection via refined allergen risk assessment that is independent of the type of tissue or food processing method used.

Parvalbumin Regulates GAD Expression through Calcium Ion Concentration to Affect the Balance of Glu-GABA and Improve KA-Induced Status Epilepticus in PV-Cre Transgenic Mice.

Aims: the study aimed to (i) use adeno-associated virus technology to modulate parvalbumin (PV) gene expression, both through overexpression and silencing, within the hippocampus of male mice and (ii) assess the impact of PV on the metabolic pathway of glutamate and γ-aminobutyric acid (GABA). Methods: a status epilepticus (SE) mouse model was established by injecting kainic acid into the hippocampus of transgenic mice. When the seizures of mice reached SE, the mice were killed at that time point and 30 min after the onset of SE. Hippocampal tissues were extracted and the mRNA and protein levels of PV and the 65 kDa (GAD65) and 67 kDa (GAD67) isoforms of glutamate decarboxylase were assessed using real-time quantitative polymerase chain reaction and Western blot, respectively. The concentrations of glutamate and GABA were detected with high-performance liquid chromatography (HPLC), and the intracellular calcium concentration was detected using flow cytometry. Results: we demonstrate that the expression of PV is associated with GAD65 and GAD67 and that PV regulates the levels of GAD65 and GAD67. PV was correlated with calcium concentration and GAD expression. Interestingly, PV overexpression resulted in a reduction in calcium ion concentration, upregulation of GAD65 and GAD67, elevation of GABA concentration, reduction in glutamate concentration, and an extension of seizure latency. Conversely, PV silencing induced the opposite effects. Conclusion: parvalbumin may affect the expression of GAD65 and GAD67 by regulating calcium ion concentration, thereby affecting the metabolic pathways associated with glutamate and GABA. In turn, this contributes to the regulation of seizure activity.

Parvalbumin interneuron cell-to-network plasticity: mechanisms and therapeutic avenues.

Alzheimer's disease (AD) and schizophrenia (SCZ) represent two major neuropathological conditions with a high disease burden. Despite their distinct etiologies, patients suffering from AD or SCZ share a common burden of disrupted memory functions unattended by current therapies. Recent preclinical analyses highlight cell-type-specific contributions of parvalbumin interneurons (PVIs), particularly the plasticity of their cellular excitability, towards intact neuronal network function (cell-to-network plasticity) and memory performance. Here we argue that deficits of PVI cell-to-network plasticity may underlie memory deficits in AD and SCZ, and we explore two therapeutic avenues: the targeting of PVI-specific neuromodulation, including by neuropeptides, and the recruitment of network synchrony in the gamma frequency range (40 Hz) by external stimulation. We finally propose that these approaches be merged under consideration of recent insights into human brain physiology.

Nr4a1 regulates cell-specific transcriptional programs in inhibitory GABAergic interneurons.

The patterns of synaptic connectivity and physiological properties of diverse neuron types are shaped by distinct gene sets. Our study demonstrates that, in the mouse forebrain, the transcriptional profiles of inhibitory GABAergic interneurons are regulated by Nr4a1, an orphan nuclear receptor whose expression is transiently induced by sensory experiences and is required for normal learning. Nr4a1 exerts contrasting effects on the local axonal wiring of parvalbumin- and somatostatin-positive interneurons, which innervate different subcellular domains of their postsynaptic partners. The loss of Nr4a1 activity in these interneurons results in bidirectional, cell-type-specific transcriptional switches across multiple gene families, including those involved in surface adhesion and repulsion. Our findings reveal that combinatorial synaptic organizing codes are surprisingly flexible and highlight a mechanism by which inducible transcription factors can influence neural circuit structure and function.

Closed-loop recruitment of striatal interneurons prevents compulsive-like grooming behaviors.

Compulsive behaviors have been associated with striatal hyperactivity. Parvalbumin-positive striatal interneurons (PVIs) in the striatum play a crucial role in regulating striatal activity and suppressing prepotent inappropriate actions. To investigate the potential role of striatal PVIs in regulating compulsive behaviors, we assessed excessive self-grooming-a behavioral metric of compulsive-like behavior-in male Sapap3 knockout mice (Sapap3-KO). Continuous optogenetic activation of PVIs in striatal areas receiving input from the lateral orbitofrontal cortex reduced self-grooming events in Sapap3-KO mice to wild-type levels. Aiming to shorten the critical time window for PVI recruitment, we then provided real-time closed-loop optogenetic stimulation of striatal PVIs, using a transient power increase in the 1-4 Hz frequency band in the orbitofrontal cortex as a predictive biomarker of grooming onsets. Targeted closed-loop stimulation at grooming onsets was as effective as continuous stimulation in reducing grooming events but required 87% less stimulation time, paving the way for adaptive stimulation therapeutic protocols.

CCK+ Interneurons Contribute to Thalamus-Evoked Feed-Forward Inhibition in the Prelimbic Prefrontal Cortex.

Interneurons in the medial prefrontal cortex (PFC) regulate local neural activity to influence cognitive, motivated, and emotional behaviors. Parvalbumin-expressing (PV+) interneurons are the primary mediators of thalamus-evoked feed-forward inhibition across the mouse cortex, including the anterior cingulate cortex, where they are engaged by inputs from the mediodorsal (MD) thalamus. In contrast, in the adjacent prelimbic (PL) cortex, we find that PV+ interneurons are scarce in the principal thalamorecipient layer 3 (L3), suggesting distinct mechanisms of inhibition. To identify the interneurons that mediate MD-evoked inhibition in PL, we combine slice physiology, optogenetics, and intersectional genetic tools in mice of both sexes. We find interneurons expressing cholecystokinin (CCK+) are abundant in L3 of PL, with cells exhibiting fast-spiking (fs) or non-fast-spiking (nfs) properties. MD inputs make stronger connections onto fs-CCK+ interneurons, driving them to fire more readily than nearby L3 pyramidal cells and other interneurons. CCK+ interneurons in turn make inhibitory, perisomatic connections onto L3 pyramidal cells, where they exhibit cannabinoid 1 receptor (CB1R) mediated modulation. Moreover, MD-evoked feed-forward inhibition, but not direct excitation, is also sensitive to CB1R modulation. Our findings indicate that CCK+ interneurons contribute to MD-evoked inhibition in PL, revealing a mechanism by which cannabinoids can modulate MD-PFC communication.