Autapses selectively form in specific cell types in many brain regions. Previous studies have also found putative autapses in principal spiny projection neurons (SPNs) in the striatum. However, it remains unclear whether these neurons indeed form physiologically functional autapses. We applied whole-cell recording in striatal slices and identified autaptic cells by the occurrence of prolonged asynchronous release (AR) of neurotransmitters after bursts of high-frequency action potentials (APs). Surprisingly, we found no autaptic AR in SPNs, even in the presence of Sr²⁺. However, robust autaptic AR was recorded in parvalbumin (PV)-expressing neurons. The autaptic responses were mediated by GABA_A receptors and their strength was dependent on AP frequency and number. Further computer simulations suggest that autapses regulate spiking activity in PV cells by providing self-inhibition and thus shape network oscillations. Together, our results indicate that PV neurons, but not SPNs, form functional autapses, which may play important roles in striatal functions.
Parvalbumins/metabolism* ; Corpus Striatum/metabolism* ; Interneurons/physiology* ; Neurons/metabolism* ; Neostriatum

Afferent Pathways ; Animals ; Female ; Nerve Block ; Olfactory Bulb ; metabolism ; Parvalbumins ; metabolism ; Rats ; Rats, Wistar

Cortical GABAergic inhibitory neurons are composed of three major classes, each expressing parvalbumin (PV), somatostatin (SOM) and 5-hydroxytryptamine receptor 3A (Htr3a), respectively. Htr3a
Animals ; Interneurons/metabolism* ; Mice ; Neurons/metabolism* ; Parvalbumins/metabolism* ; Receptors, Serotonin, 5-HT3/genetics* ; Serotonin ; Somatostatin/metabolism*

OBJECTIVE: To investigate the auditory response patterns of mouse primary auditory cortex (A1) neurons. METHODS: In vivo cell-attached recordings and neural network modeling were performed to detect the changes in response patterns of A1 neurons of awake C57BL/6J mice to sound stimulation with varying lengths. A1 neuron signals were recorded for 216 neurons in 20 awake mice using a target sound stimulation sequence, and the classification and response characteristics of A1 neuron response patterns were examined using post-stimulus spike time histograms. To simulate the diversity of the A1 neuron response patterns, an A1 neuron model was established based on the Wilson-Cowan model and integral-firing model. The neuron connection weight parameters in the model were calculated by examining the micro loop structure of the pyramidal neurons, parvalbumin neurons, and somatostatin neurons in the A1 region, and the A1 neural network information coding model was constructed. RESULTS: The Onset response neurons only had fast spike response within 10 to 40 ms after the beginning of noise stimulation (122 neurons). The Sustained response neurons had spike response continuously during the noise stimulation (26 neurons). The On-off response neurons had fast spike response after the beginning and the end of noise stimulation (40 neurons). The Offset response neurons only had fast spike response within 10 to 40 ms after the end of noise stimulation (22 neurons). In the neural network model, the Onset peak neural activities of A1 pyramidal neurons, parvalbumin neurons, and somatostatin neurons were 0.7483, 0.5236 and 0.9427, respectively, and their response half peak widths were 18.5 ms, 12 ms and 31 ms during the 100 ms noise stimulation, respectively. By changing the feedforward excitation and synaptic inhibition time constants in the model, the neurons generated numerous different types of spike train. CONCLUSION The auditory response of mouse A1 neurons to sound stimuli shows mainly the Onset, Sustained, On-off, and Offset response patterns.
Acoustic Stimulation ; Animals ; Auditory Cortex/physiology* ; Mice ; Mice, Inbred C57BL ; Parvalbumins ; Somatostatin

This study aims to explore the electrophysiological properties and changes in gene expression of basket cells, a unique population of GABAergic interneurons expressing parvalbumin (PV), during the postnatal development of mouse prefrontal cortex (PFC). Toward this goal, we took use of the G42 transgenic mouse line which specifically expresses enhanced green fluorescent protein (EGFP) in basket cells. The brain slices of PFC were prepared from the postnatal 7 (P7), 14 (P14) and 21 days (P42) G42 mice and whole-cell patch clamp recording was performed in basket cells. In addition, we sorted the basket cells by flow cytometry and analyzed their transcription profiling on P7, P14, and P21 using RNA-seq technology. The results showed that the resting membrane potential and membrane input resistance decreased gradually from P7 to P21. The amplitude and duration of action potential of basket cells increased and decreased from P7 to P21, respectively. In contrast, the threshold of action potential of basket cells did not have a significant change from P7 to P21. The frequency of spontaneous excitatory postsynaptic currents (sEPSCs) of basket cells increased gradually, while the amplitudes of sEPSCs of basket cells remained constant from P7 to P21. RNA sequencing from basket cells revealed that the expression of 22 and 660 genes was upregulated and downregulated from P7 to P14, respectively. By contrast, the expression of 107 and 69 genes was upregulated and downregulated from P14 to P21, respectively. The differentially expressed genes in basket cells from P7 to P21 were significantly enriched in pathways such as neuron apoptotic process, mRNA processing, Golgi vesicle transport and axon guidance. Altogether, we characterized electrophysiological properties and changes in gene expression of basket cells during the postnatal development in mouse PFC. These results provide insight into the mechanisms underlying the development of basket cells in mouse cortex.
Animals ; Gene Expression ; Interneurons/metabolism* ; Mice ; Mice, Transgenic ; Parvalbumins/metabolism* ; Prefrontal Cortex/metabolism*

The α2A adrenoceptors (α2A-ARs) are the most common adrenergic receptor subtype found in the prefrontal cortex (PFC). It is generally accepted that stimulation of postsynaptic α2A-ARs on pyramidal neurons are key to PFC functions, such as working memory. However, the expression of α2A-ARs in interneurons is largely unknown. In the present study using double-labeling immunofluorencence technique, we investigated the expression of α2A-ARs in major types of rat PFC interneurons expressing calcium-binding proteins parvalbumin (PV), calretinin (CR), and calbindin (CB). Our data demonstrated that α2A-ARs are highly expressed in calcium-binding protein immunoreactive interneurons of rat PFC, suggesting that stimulation of α2A-ARs may alter neural networks comprising pyramidal neurons and interneurons, thereby exerting a beneficial effect on PFC cognitive functions. The present study provides the morphological basis for a potential mechanism by which stimulation of α2A-ARs induces cognitive improvement.
Animals ; Calbindin 2 ; metabolism ; Calbindins ; metabolism ; Interneurons ; metabolism ; Parvalbumins ; metabolism ; Prefrontal Cortex ; cytology ; Rats ; Receptors, Adrenergic, alpha-2 ; metabolism

A strong animal survival instinct is to approach objects and situations that are of benefit and to avoid risk. In humans, a large proportion of mental disorders are accompanied by impairments in risk avoidance. One of the most important genes involved in mental disorders is disrupted-in-schizophrenia-1 (DISC1), and animal models in which this gene has some level of dysfunction show emotion-related impairments. However, it is not known whether DISC1 mouse models have an impairment in avoiding potential risks. In the present study, we used DISC1-N terminal truncation (DISC1-N
Animals ; Interneurons/metabolism* ; Mice ; Mice, Transgenic ; Nerve Tissue Proteins/metabolism* ; Neurons/metabolism* ; Nucleus Accumbens/metabolism* ; Parvalbumins/metabolism*

Parvalbumin interneurons belong to the major types of GABAergic interneurons. Although the distribution and pathological alterations of parvalbumin interneuron somata have been widely studied, the distribution and vulnerability of the neurites and fibers extending from parvalbumin interneurons have not been detailly interrogated. Through the Cre recombinase-reporter system, we visualized parvalbumin-positive fibers and thoroughly investigated their spatial distribution in the mouse brain. We found that parvalbumin fibers are widely distributed in the brain with specific morphological characteristics in different regions, among which the cortex and thalamus exhibited the most intense parvalbumin signals. In regions such as the striatum and optic tract, even long-range thick parvalbumin projections were detected. Furthermore, in mouse models of temporal lobe epilepsy and Parkinson's disease, parvalbumin fibers suffered both massive and subtle morphological alterations. Our study provides an overview of parvalbumin fibers in the brain and emphasizes the potential pathological implications of parvalbumin fiber alterations.
Mice ; Animals ; Epilepsy, Temporal Lobe/pathology* ; Parvalbumins/metabolism* ; Parkinson Disease/pathology* ; Neurons/metabolism* ; Interneurons/physiology* ; Disease Models, Animal ; Brain/pathology*

The circling mice with tmie gene mutation are known as an animal deafness model, which showed hyperactive circling movement. Recently, the reinvestigation of circling mouse was performed to check the inner ear pathology as a main lesion of early hearing loss. In this trial, the inner ear organs were not so damaged to cause the hearing deficit of circling (cir/cir) mouse at 18 postnatal day (P18) though auditory brainstem response data indicated hearing loss of cir/cir mice at P18. Thus, another mechanism may be correlated with the early hearing loss of cir/cir mice at P18. Hearing loss in the early life can disrupt the ascending and descending information to inferior colliculus (IC) as integration site. There were many reports that hearing loss could result in the changes in Ca²⁺ concentration by either cochlear ablation or genetic defect. However, little was known to be reported about the correlation between the pathology of IC and Ca²⁺ changes in circling mice. Therefore, the present study investigated the distribution of calcium-binding proteins (CaBPs), calbindin-D28k, parvalbumin, and calretinin immunoreactivity (IR) in the IC to compare among wild-type (+/+), heterozygous (+/cir), and homozygous (cir/cir) mice by immunohistochemistry. The decreases of CaBPs IR in cir/cir were statistically significant in the neurons as well as neuropil of IC. Thus, this study proposed overall distributional alteration of CaBPs IR in the IC caused by early hearing defect and might be helpful to elucidate the pathology of central auditory disorder related with Ca²⁺ metabolism.
Animals ; Calbindin 1* ; Calbindin 2* ; Calcium-Binding Proteins ; Deafness ; Ear, Inner ; Evoked Potentials, Auditory, Brain Stem ; Hearing ; Hearing Loss ; Immunohistochemistry ; Inferior Colliculi* ; Metabolism ; Mice* ; Neurons ; Neuropil ; Parvalbumins ; Pathology

BACKGROUNDParvalbumin (PV), as a mobile endogenous calcium buffer, plays an important role in affecting temporospatial characteristics of calcium transients and in modulating calcium homeostasis. PV is expressed in neurons in the dorsal root ganglion (DRG) and spinal dorsal horn and may be involved in synaptic transmission through regulating cytoplasm calcium concentrations. But the exact role of PV in peripheral sensory neurons remains unknown. Microtubule-associated protein 2 (MAP-2), belonging to structural microtubule-associated protein family, is especially vulnerable to acute central nervous system (CNS) injury, and there will be rapid loss of MAP-2 at the injury site. The present study investigated the changes of PV expressing neurons and the MAP-2 neurons in the DRG after an operation for chronic constriction injury to the unilateral sciatic nerve (CCI-SN), in order to demonstrate the possible roles of PV and MAP-2 in transmission and modulation of peripheral nociceptive information.

METHODSSeventy-two adult male Sprague-Dawley (SD) rats, weighing 180 - 220 g, were randomly divided into two groups (36 rats in each group), the sham operation group and chronic constriction injury (CCI) group. Six rats in each group were randomly selected to receive mechanical and thermal sensitivity tests at one day before operation and 1, 3, 5, 7, and 14 days after surgery. After pain behavioral test, ipsilateral lumbar fifth DRGs were removed and double immunofluorescence staining was performed to assess the expression changes of PV and of MAP2 expressing neurons in the L5 DRG before or after surgery.

RESULTSThe animals with CCI-SN showed obvious mechanical allodynia and thermal hyperalgesia (P < 0.05). Both the thermal and mechanical hyperalgesia decreased to their lowest degree at 7 days after surgery compared to the baseline before surgery (P < 0.01). In normal rats before surgery, a large number of neurons were MAP-2 single labeled cells, and just a small number of PV-expressed neurons were found. PV-positive neurons, PV-positive nerve fibers and PV-negative neurons, formed a direct or close contact for cross-talk. We used immunocytochemical staining to quantify the time course of changes to PV and MAP-2 expressing neurons in tissue, and found that the number of PV expressing neurons began to slightly decrease at 3 days after surgery, and had a significant reduction at CCI day 5, day 7 (P < 0.05). But MAP-2 neurons significantly decreased on just the 3rd day after CCI (P < 0.05). No changes in PV and MAP-2 expression were almost found in sham operated rats. The number of PV positive neurons, was positively correlated with the hyperalgesia threshold.

CONCLUSIONSA sharp decline in MAP-2 neurons may be the early response to surgical injury, and PV positive neurons were much more effective at affecting the changes of pain behaviors, indicating that the down-regulation of PV protein could participate in, at least in part, the modulation of nociceptive transmission.

Animals ; Constriction, Pathologic ; Ganglia, Spinal ; metabolism ; pathology ; Immunohistochemistry ; Male ; Microtubule-Associated Proteins ; metabolism ; Neurons ; metabolism ; Parvalbumins ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Sciatic Neuropathy ; metabolism ; pathology