OBJECTIVES: To investigate the mechanism by which the pyramidal neurons of the anterior cingulate cortex (ACC) modulate the effects of enriched environment (EE) for relieving anxiety-like behaviors in mice. METHODS: C57BL/6J mice were randomly divided into control group, restraint stress (RS) group, and RS+EE group (n=8). The mice in the latter two groups were subjected to RS for 2 h daily for 3 days, and those in RS+EE group were housed in an EE during modeling. Anxiety-like behaviors of the mice were evaluated using the elevated plus-maze tests (EPM) and open field test (OFT). Changes in c-Fos expression in the ACC of the mice were detected with immunofluorescence assay, and pyramidal neuron excitability in the ACC (Pyn^ACC) was measured using patch-clamp technique. The miniature excitatory and inhibitory postsynaptic currents (mEPSC and mIPSC, respectively) were analyzed to assess synaptic transmission changes. RESULTS: Behavioral tests showed obvious anxiety-like behaviors in RS mice, and such behavioral changes were significantly improved in RS+EE mice. Immunofluorescence staining revealed significantly increased c-Fos expression in the ACC in RS mice but lowered c-Fos expression in RS+EE group. Compared with the control mice, the RS mice showed increased action potential firing rate of Pyn^ACC, which was significantly reduced in RS+EE group. Compared with the RS mice, the RS+EE mice showed also decreased frequency of mEPSCs of Pyn^ACC, but the amplitude exhibited no significant changes. No obvious changes in the frequency or amplitude of mIPSCs were observed in RS+EE mice. CONCLUSIONS EE reduces excitability of Pyn^ACC to alleviate anxiety-like behaviors induced by RS in mice.
Animals ; Anxiety/physiopathology* ; Gyrus Cinguli ; Mice, Inbred C57BL ; Mice ; Pyramidal Cells/physiology* ; Restraint, Physical ; Stress, Psychological ; Proto-Oncogene Proteins c-fos/metabolism* ; Male ; Behavior, Animal ; Environment ; Excitatory Postsynaptic Potentials

Anxiety disorder is a major symptom of autism spectrum disorder (ASD) with a comorbidity rate of ~40%. However, the neural mechanisms of the emergence of anxiety in ASD remain unclear. In our study, we found that hyperactivity of basolateral amygdala (BLA) pyramidal neurons (PNs) in Shank3 InsG3680 knock-in (InsG3680^+/+) mice is involved in the development of anxiety. Electrophysiological results also showed increased excitatory input and decreased inhibitory input in BLA PNs. Chemogenetic inhibition of the excitability of PNs in the BLA rescued the anxiety phenotype of InsG3680^+/+ mice. Further study found that the diminished control of the BLA by medial prefrontal cortex (mPFC) and optogenetic activation of the mPFC-BLA pathway also had a rescue effect, which increased the feedforward inhibition of the BLA. Taken together, our results suggest that hyperactivity of the BLA and alteration of the mPFC-BLA circuitry are involved in anxiety in InsG3680^+/+ mice.
Animals ; Prefrontal Cortex/metabolism* ; Basolateral Nuclear Complex/metabolism* ; Mice ; Anxiety/metabolism* ; Nerve Tissue Proteins/genetics* ; Male ; Gene Knock-In Techniques ; Pyramidal Cells/physiology* ; Mice, Transgenic ; Neural Pathways/physiopathology* ; Mice, Inbred C57BL ; Microfilament Proteins

Differing from other subtypes of inhibitory interneuron, chandelier or axo-axonic cells form depolarizing GABAergic synapses exclusively onto the axon initial segment (AIS) of targeted pyramidal cells (PCs). However, the debate whether these AIS-GABAergic inputs produce excitation or inhibition in neuronal processing is not resolved. Using realistic NEURON modeling and electrophysiological recording of cortical layer-5 PCs, we quantitatively demonstrate that the onset-timing of AIS-GABAergic input, relative to dendritic excitatory glutamatergic inputs, determines its bi-directional regulation of the efficacy of synaptic integration and spike generation in a PC. More specifically, AIS-GABAergic inputs promote the boosting effect of voltage-activated Na⁺ channels on summed synaptic excitation when they precede glutamatergic inputs by >15 ms, while for nearly concurrent excitatory inputs, they primarily produce a shunting inhibition at the AIS. Thus, our findings offer an integrative mechanism by which AIS-targeting interneurons exert sophisticated regulation of the input-output function in targeted PCs.
Axon Initial Segment ; Axons/physiology* ; Neurons ; Synapses/physiology* ; Pyramidal Cells/physiology* ; Interneurons/physiology* ; Action Potentials/physiology*

The anterior auditory field (AAF) is a core region of the auditory cortex and plays a vital role in discrimination tasks. However, the role of the AAF corticostriatal neurons in frequency discrimination remains unclear. Here, we used c-Fos staining, fiber photometry recording, and pharmacogenetic manipulation to investigate the function of the AAF corticostriatal neurons in a frequency discrimination task. c-Fos staining and fiber photometry recording revealed that the activity of AAF pyramidal neurons was significantly elevated during the frequency discrimination task. Pharmacogenetic inhibition of AAF pyramidal neurons significantly impaired frequency discrimination. In addition, histological results revealed that AAF pyramidal neurons send strong projections to the striatum. Moreover, pharmacogenetic suppression of the striatal projections from pyramidal neurons in the AAF significantly disrupted the frequency discrimination. Collectively, our findings show that AAF pyramidal neurons, particularly the AAF-striatum projections, play a crucial role in frequency discrimination behavior.
Acoustic Stimulation/methods* ; Neurons/physiology* ; Auditory Cortex/physiology* ; Auditory Perception ; Pyramidal Cells

The axon initial segment (AIS) is a highly specialized axonal compartment where the action potential is initiated. The heterogeneity of AISs has been suggested to occur between interneurons and pyramidal neurons (PyNs), which likely contributes to their unique spiking properties. However, whether the various characteristics of AISs can be linked to specific PyN subtypes remains unknown. Here, we report that in the prelimbic cortex (PL) of the mouse, two types of PyNs with axon projections either to the contralateral PL or to the ipsilateral basal lateral amygdala, possess distinct AIS properties reflected by morphology, ion channel expression, action potential initiation, and axo-axonic synaptic inputs from chandelier cells. Furthermore, projection-specific AIS diversity is more prominent in the superficial layer than in the deep layer. Thus, our study reveals the cortical layer- and axon projection-specific heterogeneity of PyN AISs, which may endow the spiking of various PyN types with exquisite modulation.
Mice ; Animals ; Axon Initial Segment ; Synapses/physiology* ; Pyramidal Cells/physiology* ; Cerebral Cortex ; Axons/physiology*

The back-propagating action potential (bpAP) is crucial for neuronal signal integration and synaptic plasticity in dendritic trees. Its properties (velocity and amplitude) can be affected by dendritic morphology. Due to limited spatial resolution, it has been difficult to explore the specific propagation process of bpAPs along dendrites and examine the influence of dendritic morphology, such as the dendrite diameter and branching pattern, using patch-clamp recording. By taking advantage of Optopatch, an all-optical electrophysiological method, we made detailed recordings of the real-time propagation of bpAPs in dendritic trees. We found that the velocity of bpAPs was not uniform in a single dendrite, and the bpAP velocity differed among distinct dendrites of the same neuron. The velocity of a bpAP was positively correlated with the diameter of the dendrite on which it propagated. In addition, when bpAPs passed through a dendritic branch point, their velocity decreased significantly. Similar to velocity, the amplitude of bpAPs was also positively correlated with dendritic diameter, and the attenuation patterns of bpAPs differed among different dendrites. Simulation results from neuron models with different dendritic morphology corresponded well with the experimental results. These findings indicate that the dendritic diameter and branching pattern significantly influence the properties of bpAPs. The diversity among the bpAPs recorded in different neurons was mainly due to differences in dendritic morphology. These results may inspire the construction of neuronal models to predict the propagation of bpAPs in dendrites with enormous variation in morphology, to further illuminate the role of bpAPs in neuronal communication.
Action Potentials/physiology* ; Dendrites/physiology* ; Neurons/physiology* ; Neuronal Plasticity ; Pyramidal Cells/physiology*

Diverse types of GABAergic interneurons tend to specialize in their inhibitory control of various aspects of cortical circuit operations. Among the most distinctive interneuron types, chandelier cells (i.e., axo-axonic cells) are a bona fide cell type that specifically innervates pyramidal cells at the axon initial segment, the site of action potential initiation. Chandelier cells have been speculated to exert ultimate inhibitory control over pyramidal cell spiking. Thus, chandelier cells appear to share multiple similarities with basket cells, not only in firing pattern (fast spiking) and molecular components, but also in potentially perisomatic inhibitory control. Unlike basket cells, however, synaptic recruitment of chandelier cells is little known yet. Here, we examined the mediodorsal thalamocortical input to both chandelier cells and basket cells in medial prefrontal cortex, through combining mouse genetic, optogenetic and electrophysiological approaches. We demonstrated that this thalamocortical input produced initially weak, but facilitated synaptic responses at chandelier cells, which enabled chandelier cells to spike persistently. In contrast, this thalamocortical input evoked initially strong, but rapidly depressed synaptic responses at basket cells, and basket cells only fired at the initiation of input. Overall, the distinct synaptic recruitment dynamics further underscores the differences between chandelier cells and basket cells, suggesting that these two types of fast spiking interneurons play different roles in cortical circuit processing and physiological operation.
Mice ; Animals ; Neurons/physiology* ; Pyramidal Cells/physiology* ; Interneurons ; Action Potentials/physiology* ; Synaptic Transmission

OBJECTIVE: To investigate the effects of acid-sensing ion channels (ASICs) on electrophysiological epileptic activities of mouse hippocampal pyramidal neurons in the extracellular acidotic condition. METHODS: We investigated effects of extracellular acidosis on epileptic activities induced by elevated extracellular K concentration or the application of an antagonist of GABA receptors in perfusate of mouse hippocampal slices under field potential recordings. We also tested the effects of extracellular acidosis on neuronal excitability under field potential recording and evaluated the changes in epileptic activities of the neurons in response to pharmacological inhibition of ASICs using a specific inhibitor of ASICs. RESULTS: Extracellular acidosis significantly suppressed epileptic activities of the hippocampal neurons by converting ictal-like epileptic activities to non-ictal-like epileptic activities in both high [K ]o and disinhibition models, and also suppressed the intrinsic excitability of the neurons. ASICs inhibitor did not antagonize the inhibitory effect of extracellular acidosis on ictal epileptic activities and intrinsic neuronal excitability, but exacerbated non-ictal epileptic activities of the neurons in extracellular acidotic condition in both high [K]o and disinhibition models. CONCLUSIONS ASICs can differentially modulate ictal-like and non-ictallike epileptic activities via its direct actions on excitatory neurons.
Acid Sensing Ion Channels ; metabolism ; Acidosis ; Animals ; Epilepsy ; physiopathology ; Hydrogen-Ion Concentration ; Mice ; Pyramidal Cells ; pathology ; physiology

Neuroligins (NLs) are postsynaptic cell-adhesion proteins that play important roles in synapse formation and the excitatory-inhibitory balance. They have been associated with autism in both human genetic and animal model studies, and affect synaptic connections and synaptic plasticity in several brain regions. Yet current research mainly focuses on pyramidal neurons, while the function of NLs in interneurons remains to be understood. To explore the functional difference among NLs in the subtype-specific synapse formation of both pyramidal neurons and interneurons, we performed viral-mediated shRNA knockdown of NLs in cultured rat cortical neurons and examined the synapses in the two major types of neurons. Our results showed that in both types of neurons, NL1 and NL3 were involved in excitatory synapse formation, and NL2 in GABAergic synapse formation. Interestingly, NL1 affected GABAergic synapse formation more specifically than NL3, and NL2 affected excitatory synapse density preferentially in pyramidal neurons. In summary, our results demonstrated that different NLs play distinct roles in regulating the development and balance of excitatory and inhibitory synapses in pyramidal neurons and interneurons.
Animals ; Cell Adhesion Molecules, Neuronal ; physiology ; Cells, Cultured ; Cerebral Cortex ; embryology ; physiology ; GABAergic Neurons ; physiology ; Interneurons ; physiology ; Membrane Proteins ; physiology ; Nerve Tissue Proteins ; physiology ; Protein Isoforms ; physiology ; Pyramidal Cells ; physiology ; Rats, Sprague-Dawley ; Synapses ; physiology

Cognition and pain share common neural substrates and interact reciprocally: chronic pain compromises cognitive performance, whereas cognitive processes modulate pain perception. In the present study, we established a non-drug-dependent rat model of context-based analgesia, where two different contexts (dark and bright) were matched with a high (52°C) or low (48°C) temperature in the hot-plate test during training. Before and after training, we set the temperature to the high level in both contexts. Rats showed longer paw licking latencies in trials with the context originally matched to a low temperature than those to a high temperature, indicating successful establishment of a context-based analgesic effect in rats. This effect was blocked by intraperitoneal injection of naloxone (an opioid receptor antagonist) before the probe. The context-based analgesic effect also disappeared after optogenetic activation or inhibition of the bilateral infralimbic or prelimbic sub-region of the prefrontal cortex. In brief, we established a context-based, non-drug dependent, placebo-like analgesia model in the rat. This model provides a new and useful tool for investigating the cognitive modulation of pain.
Action Potentials ; drug effects ; physiology ; Analgesics ; pharmacology ; therapeutic use ; Animals ; Disease Models, Animal ; Electric Stimulation ; Female ; In Vitro Techniques ; Naloxone ; pharmacology ; Narcotic Antagonists ; pharmacology ; Optogenetics ; Pain ; drug therapy ; pathology ; physiopathology ; Pain Measurement ; drug effects ; Pain Threshold ; drug effects ; physiology ; Patch-Clamp Techniques ; Physical Stimulation ; Prefrontal Cortex ; drug effects ; metabolism ; pathology ; Pyramidal Cells ; drug effects ; physiology ; Rats ; Rats, Sprague-Dawley ; Time Factors