Parvalbumin mRNA Research Articles

Opposite effect of phencyclidine on activity-regulated cytoskeleton-associated protein (Arc) in juvenile and adult limbic rat brain regions

The psychotomimetic effect of NMDA antagonists such as phencyclidine (PCP) in humans spurred the hypoglutamatergic theory of schizophrenia. This theory is supported by animal studies demonstrating schizophrenia-like behavioral and molecular changes following PCP administration to adult or neonatal animals. However, schizophrenia is believed to develop in part due to neurodevelopmental dysfunction during adolescence. Therefore, the effects of PCP in juvenile animals may better reflect the pathophysiology of schizophrenia. Here, we compare the effect of PCP (5 mg/kg/day for 5 days) on activity-regulated cytoskeleton-associated protein (Arc) and parvalbumin mRNA expression in juvenile and adult rats. Arc is a marker for excitatory neurotransmission. Parvalbumin is a marker for GABAergic neurotransmission, known to be reduced in postmortem brains of schizophrenics. PCP reduced parvalbumin mRNA expression in the medial prefrontal cortex (mPFC), ventrolateral orbitofrontal cortex (VLO) and shell of the nucleus accumbens (ACCshell) in both juvenile and adult rats. Contrarily, PCP produced opposite effects on Arc mRNA expression in the mPFC, VLO and ACCshell, leading to decreased expression in juvenile and increased expression in adult rats. The differential effect of PCP in juvenile and adult rats may be caused by the immature functional state of the prefrontal cortex in juvenile rats. These results demonstrate differences between the effects of PCP in juvenile and adult rats. The decrease in Arc mRNA in juvenile rats corresponds best with the proposed “hypofrontality” in schizophrenia, suggesting the merits of using PCP in juvenile animals as a model for schizophrenia, as this would relate better to the typical onset and clinical features of schizophrenia.

α 7 Nicotinic acetylcholine receptor activation prevents behavioral and molecular changes induced by repeated phencyclidine treatment

The core features of schizophrenia include deficits in cognitive processes, such as attention and working memory, subserved by the prefrontal cortex (PFC). These deficits are believed to involve deficient neurotransmission through NMDA receptors, particularly on parvalbumin-containing interneurons, and administration of the NMDA-antagonist phencyclidine (PCP) in rodents is a well validated model of such cognitive deficits. Here we show that repeated PCP treatment (10 mg/kg/day for 10 days) decreased the expression of parvalbumin and synaptophysin mRNA in the mouse PFC, which corresponds to changes seen in patients with schizophrenia. In addition, PCP increased the basal mRNA expression in the PFC of the activity-regulated cytoskeleton-associated protein (Arc), a molecule involved in synaptic plasticity. These molecular changes produced by PCP were accompanied by a behavioral impairment as determined in a modified Y-maze test. Polymorphisms in the α 7 nicotinic acetylcholine receptor (nAChR) gene have been linked to schizophrenia. Here we demonstrate that acute administration of the selective α 7 nAChR partial agonist SSR180711 dose-dependently reversed the behavioral impairment induced by PCP. Importantly, repeated co-administration of SSR180711 (3 mg/kg) with PCP prevented both the changes in parvalbumin, synaptophysin, and Arc mRNA expression in the PFC, and the behavioral impairment induced by PCP. These results are the first to demonstrate prevention of the deleterious effects induced by repeated PCP treatment. The behavioral and molecular effects of α 7 nAChR agonism in this model, particularly the prevention of a decline in parvalbumin mRNA expression, suggest an involvement of the α 7 nAChR not only in the symptomatic relief, but also the pathophysiology, of schizophrenia.

Molecular Determinants of Dysregulated GABAergic Gene Expression in the Prefrontal Cortex of Subjects with Schizophrenia

Prefrontal deficits in gamma-aminobutyric acid (GABA)ergic gene expression, including neuropeptide Y (NPY), somatostatin (SST), and parvalbumin (PV) messenger RNAs (mRNAs), have been reported for multiple schizophrenia cohorts. Preclinical models suggest that a subset of these GABAergic markers (NPY/SST) is regulated by brain-derived neurotrophic factor (BDNF), which in turn is under the inhibitory influence of small noncoding RNAs. However, it remains unclear if these mechanisms are important determinants for dysregulated NPY and SST expression in prefrontal cortex (PFC) of subjects with schizophrenia. Using a postmortem case-control design, the association between BDNF protein, NPY/SST/PV mRNAs, and two BDNF-regulating microRNAs (miR-195 and miR-30a-5p) was determined in samples from the PFC of 20 schizophrenia and 20 control subjects. Complementary studies were conducted in cerebral cortex of mice subjected to antipsychotic treatment or a brain-specific ablation of the Bdnf gene. Subjects with schizophrenia showed deficits in NPY and PV mRNAs. Within-pair differences in BDNF protein levels showed strong positive correlations with NPY and SST and a robust inverse association with miR-195 levels, which in turn were not affected by antipsychotic treatment or genetic ablation of Bdnf. Taken together, these results suggest that prefrontal deficits in a subset of GABAergic mRNAs, including NPY, are dependent on the regional supply of BDNF, which in turn is fine-tuned through a microRNA (miRNA)-mediated mechanism.

Parvalbumin mRNA in raw and processed fillet of rainbow trout Oncorhynchus mykiss: determination of copy number and stability against heat and acid

Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) has been developed for determination of short sequences (∼120 nucleotides) of parvalbumin mRNA. The assay consisted of two steps. At first mRNA was transcribed to cDNA using primers specific for parvalbumin RNA. In the second step cDNA was quantified by real-time PCR with the LightCycler FastStart DNA Master SYBR Green I (Roche Applied Science, Mannheim, Germany). High copy numbers of mRNA, up to 109/g wet weight, have been measured in fillets of rainbow trout. Degradation of mRNA was not observed in cases of cooked, hot-smoked or acidified fish muscle, but storage of minced and washed raw muscle led to some reduction of copy numbers.

Functional and molecular development of striatal fast‐spiking GABAergic interneurons and their cortical inputs

Despite their small number, fast-spiking (FS) GABAergic interneurons play a critical role in controlling striatal output by mediating cortical feed-forward inhibition of striatal medium-sized spiny (MS) projection neurons. We have examined the functional development of FS interneurons and their cortical inputs, and the expression of three of their molecular markers, in the dorsolateral rat striatum between postnatal days (P)12--14 and 19--23, the time of major corticostriatal synaptogenesis. FS interneurons were visualized with infrared differential interference contrast (IR-DIC) optics and examined with current-clamp recording in the presence of the GABA(A) receptor antagonist bicuculline methiodide. FS interneurons displayed action potentials at relatively high frequencies in response to depolarizing current pulses by P12, but developmental changes occurred in action potential and afterhyperpolarization duration and amplitude and input resistance between P12--14 and P19--23, as well as an increase in maximum firing frequency in response to depolarizing current pulses. Maturation in electrophysiological properties was paralleled by increases in Kv 3.1 and parvalbumin mRNA expression, while GAD-67 mRNA levels remained constant. Furthermore, FS interneurons in the younger age group responded to stimulation of cortical afferents with excitatory postsynaptic potentials (EPSPs) of higher amplitudes and received significantly more spontaneous depolarizing inputs than did MS neurons. Thus, FS interneurons are under frequent and continuous cortical influence by the end of the 2nd postnatal week, a time when corticostriatal synapses are sparse, suggesting that they may provide a major inhibitory influence in the striatum during the period of intense developmental maturation.

Impairment in perceptual attentional set-shifting following PCP administration: a rodent model of set-shifting deficits in schizophrenia

Impaired ability to shift perceptual attentional set forms a core feature of schizophrenic illness and is associated with prefrontal cortical dysfunction. A pharmacological model producing equivalent deficits in rodents may enable the development of novel therapeutic strategies for effective treatment of cognitive impairments in schizophrenia. This study was designed to investigate the effects of phencyclidine (PCP) administration on performance in a rodent attentional set-shifting task and the neural correlates of PCP-induced deficits in task performance. Twenty-four hours following acute administration of 2.58 mg/kg PCP or vehicle, rats were tested on a perceptual attentional set shifting task (Birrell and Brown in J Neurosci 20:4320-4324, 2000). Following completion of the task, in situ hybridisation was employed to detect concurrent regional alterations in zif-268 and parvalbumin mRNA expression. PCP administration selectively decreased the ability of rats to shift attentional set between perceptual dimensions (extra-dimensional shift, EDS). This impairment was accompanied by, and correlated with, decreases in expression of zif-286 in the infralimbic cortex and of parvalbumin in the dorsal reticular nucleus of the thalamus. Acute administration of PCP produces deficits in perceptual set shifting comparable to an aspect of executive dysfunction in schizophrenia. Moreover, this impairment is associated with altered medial prefrontal cortical and reticular thalamic activity. Therefore, this rodent paradigm may model the set-shifting deficits that form a core feature of schizophrenic pathology.

Relationship of Brain-Derived Neurotrophic Factor and Its Receptor TrkB to Altered Inhibitory Prefrontal Circuitry in Schizophrenia

Dysfunction of inhibitory neurons in the prefrontal cortex (PFC), represented by decreased expression of GABA-related genes such as the 67 kDa isoform of glutamate decarboxylase (GAD67) and parvalbumin (PV), appears to contribute to cognitive deficits in subjects with schizophrenia. We investigated the involvement of signaling mediated by brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase TrkB in producing the altered GABA-related gene expression in schizophrenia. In 15 pairs of subjects with schizophrenia and matched control subjects, both BDNF and TrkB mRNA levels, as assessed by in situ hybridization, were significantly decreased in the PFC of the subjects with schizophrenia, whereas the levels of mRNA encoding the receptor tyrosine kinase for neurotrophin-3, TrkC, were unchanged. In this cohort, within-pair changes in TrkB mRNA levels were significantly correlated with those in both GAD67 and PV mRNA levels. Decreased BDNF, TrkB, and GAD67 mRNA levels were replicated in a second cohort of 12 subject pairs. In the combined cohorts, the correlation between within-pair changes in TrkB and GAD67 mRNA levels was significantly stronger than the correlation between the changes in BDNF and GAD67 mRNA levels. Neither BDNF nor TrkB mRNA levels were changed in the PFC of monkeys after a long-term exposure to haloperidol. Genetically introduced decreases in TrkB expression, but not in BDNF expression, also resulted in decreased GAD67 and PV mRNA levels in the PFC of adult mice; in addition, the cellular pattern of altered GAD67 mRNA expression paralleled that present in schizophrenia. Decreased TrkB signaling appears to underlie the dysfunction of inhibitory neurons in the PFC of subjects with schizophrenia.

5-HT 1A receptor mRNA and immunoreactivity in the rat medial septum/diagonal band of Broca—relationships to GABAergic and cholinergic neurons

Activation of 5-HT 1A receptors results in a variety of physiological responses, depending on their localization on neurons with different phenotypes in the brain. This study investigated the localization of 5-HT 1A receptor mRNA and 5-HT 1A receptor immunoreactivity in cell bodies of the rat septal complex using in situ hybridization and immunohistochemistry. In adjacent sections of the medial septum/diagonal band of Broca (MSDB), the distribution of cell bodies expressing 5-HT 1A receptor mRNA was closely related to cells labeled with oligonucleotide probes to GAD (glutamic acid decarboxylase), VAChT (vesicular acetylcholine transporter) or parvalbumin mRNA. Using antiserum to GAD and antibodies to GABA, 5-HT 1A receptor immunoreactivity was demonstrated in a majority of GABAergic cells in the MSDB. 5-HT 1A receptor-immunoreactive GABAergic cells in the MSDB were also demonstrated to contain the calcium-binding protein parvalbumin, a marker for septohippocampal projecting GABAergic neurons. In the lateral septum, 5-HT 1A receptor immunoreactivity was colocalized with the calcium-binding protein calbindin D-28k, a marker for septal GABAergic somatospiny neurons. 5-HT 1A receptor immunoreactivity was also detected in a subpopulation of VAChT-containing cholinergic neurons of the MSDB. In MSDB neurons, colocalization of 5-HT 1A and 5-HT 2A receptor immunoreactivities was demonstrated. These observations suggest that serotonin via 5-HT 1A receptors may represent an important modulator of hippocampal transmission important for cognitive and emotional functions through actions on both GABAergic and cholinergic neurons of the rat septal complex. In addition, 5-HT may exert its effects in the MSDB via cells expressing both 5-HT 1A and 5-HT 2A receptors.

Repeated 4-aminopyridine seizures reduce parvalbumin content in the medial mammillary nucleus of the rat brain

Parvalbumin (Pv) containing fast spiking neurons play a crucial role in synchronizing the activity of excitatory neuronal circuits in the brain. Alterations of parvalbumin content in these neurons can affect their spike characteristics and, ultimately, may increase the susceptibility of neuronal circuits to epileptic seizures. In the present study, we examined whether repeated 4-aminopyridine (4-AP)-induced seizures modify the regional parvalbumin contents in the rat brain. 4-Aminopyridine was injected intraperitoneally in adult rats, controls received the solvent. Animals were sacrificed at 3 h after a single acute treatment, or following repeated, daily treatments of 12 days. In situ hybridization (ISH) indicated significantly decreased parvalbumin mRNA level in the medial mammillary nucleus (MM) at 12 days. Western blotting revealed 20.1% significant decrease of parvalbumin content in the medial mammillary area, while parvalbumin immunohistochemistry indicated no change of the number of immunoreactive cells in the medial mammillary nucleus. The results reveal the downregulation of the transcription of the parvalbumin gene and the decrease of parvalbumin synthesis in medial mammillary nucleus neurons in response to experimental seizures.

GABA Neurons in the Human Prefrontal Cortex

Back to table of contents Previous article Next article Images in NeuroscienceFull AccessGABA Neurons in the Human Prefrontal CortexTakanori Hashimoto, M.D., Ph.D., David W. Volk, M.D., Ph.D., and David A. Lewis, M.D., Takanori HashimotoSearch for more papers by this author, M.D., Ph.D., David W. VolkSearch for more papers by this author, M.D., Ph.D., and David A. LewisSearch for more papers by this author, M.D., Pittsburgh, Pa.Published Online:22 Dec 2014https://doi.org/10.1176/ajp.161.10.1764AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail About 25% of cortical neurons utilize the inhibitory neurotransmitter, γ-aminobutyric acid (GABA). Subclasses of GABA neurons (left panel) differ in their morphological, biochemical, and functional characteristics, indicating that they likely play distinct roles in regulating cortical circuitry. Some GABA neurons (a) provide inhibitory synapses to the cell bodies of nearby excitatory pyramidal neurons (Py) and to their initial axon segments; these appear to be positioned to regulate the firing of pyramidal neurons. OtherGABA neurons (b) provide inhibitory synapses to the distal portions of pyramidal neuron dendrites, where they modulate neighboring excitatory inputs to pyramidal neurons. The synapses of a third group of GABA neurons (c) provide inhibitory inputs to other GABA neurons, resulting in a downstream “disinhibition” of pyramidal neurons. These three subclasses of GABA neurons express different calcium-binding proteins. The (a) type of GABA neurons express parvalbumin (PV), whereas the (b) and (c) types of GABA neurons express calretinin (CR). The cell type-specific expression of parvalbumin and calretinin make it possible to use the expression of the messenger RNA (mRNA) encoding each protein to study the involvement of different subclasses of GABA neurons in brain diseases. As illustrated in the center panels, contiguous sections of normal human brain tissue from Brodmann’s area 9 were processed for in situ hybridization to detect the messenger RNA for GAD67 (an enzyme that synthesizes GABA), parvalbumin, and calretinin. GAD67 mRNA is expressed by all GABA neurons that are principally found in cortical layers II-VI, but not in the subjacent white matter (WM). Parvalbumin and calretinin mRNA are expressed selectively in subpopulations of GABA neurons, and these have different distributions across the cortical layers. The right series of panels illustrates changes in mRNA expression for these proteins in the same cortical region in subjects with schizophrenia. GAD67 mRNA expression is decreased, suggesting altered prefrontal GABA-mediated neurotransmission in schizophrenia. Furthermore, the expression of parvalbumin mRNA is decreased, whereas the expression of calretinin mRNA is unchanged. These findings, as a group, suggest that prefrontal GABA neurons regulating pyramidal neuron firing are more prominently affected in schizophrenia than are other subpopulations of GABA neurons. Dysregulation of pyramidal neuron firing may contribute to cognitive dysfunction in schizophrenia.Address reprint requests to Dr. Tamminga, UT Southwestern Medical Center, Department of Psychiatry, 5323 Harry Hines Blvd., #NC5.914, Dallas, TX 75390-9070; [email protected] (e-mail). Figure. GABA Neurons in the Human Prefrontal Cortex FiguresReferencesCited byDetailsCited ByUnique gene alterations are induced in FACS-purified Fos-positive neurons activated during cue-induced relapse to heroin seeking21 November 2012 | Journal of Neurochemistry, Vol. 124, No. 1Selective epigenetic alteration of layer I GABAergic neurons isolated from prefrontal cortex of schizophrenia patients using laser-assisted microdissection30 January 2007 | Molecular Psychiatry, Vol. 12, No. 4NeuroReport, Vol. 17, No. 6The Journal of Comparative Neurology, Vol. 490, No. 3 Volume 161Issue 10 October 2004Pages 1764-1764 Metrics PDF download History Published online 22 December 2014 Published in print 1 October 2004

GABA neurons in the human prefrontal cortex.

Back to table of contents Previous article Next article Images in NeuroscienceFull AccessGABA Neurons in the Human Prefrontal CortexTakanori Hashimoto, M.D., Ph.D., David W. Volk, M.D., Ph.D., and David A. Lewis, M.D., Takanori HashimotoSearch for more papers by this author, M.D., Ph.D., David W. VolkSearch for more papers by this author, M.D., Ph.D., and David A. LewisSearch for more papers by this author, M.D., Pittsburgh, Pa.Published Online:22 Dec 2014https://doi.org/10.1176/ajp.161.10.1764AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail About 25% of cortical neurons utilize the inhibitory neurotransmitter, γ-aminobutyric acid (GABA). Subclasses of GABA neurons (left panel) differ in their morphological, biochemical, and functional characteristics, indicating that they likely play distinct roles in regulating cortical circuitry. Some GABA neurons (a) provide inhibitory synapses to the cell bodies of nearby excitatory pyramidal neurons (Py) and to their initial axon segments; these appear to be positioned to regulate the firing of pyramidal neurons. OtherGABA neurons (b) provide inhibitory synapses to the distal portions of pyramidal neuron dendrites, where they modulate neighboring excitatory inputs to pyramidal neurons. The synapses of a third group of GABA neurons (c) provide inhibitory inputs to other GABA neurons, resulting in a downstream “disinhibition” of pyramidal neurons. These three subclasses of GABA neurons express different calcium-binding proteins. The (a) type of GABA neurons express parvalbumin (PV), whereas the (b) and (c) types of GABA neurons express calretinin (CR). The cell type-specific expression of parvalbumin and calretinin make it possible to use the expression of the messenger RNA (mRNA) encoding each protein to study the involvement of different subclasses of GABA neurons in brain diseases. As illustrated in the center panels, contiguous sections of normal human brain tissue from Brodmann’s area 9 were processed for in situ hybridization to detect the messenger RNA for GAD67 (an enzyme that synthesizes GABA), parvalbumin, and calretinin. GAD67 mRNA is expressed by all GABA neurons that are principally found in cortical layers II-VI, but not in the subjacent white matter (WM). Parvalbumin and calretinin mRNA are expressed selectively in subpopulations of GABA neurons, and these have different distributions across the cortical layers. The right series of panels illustrates changes in mRNA expression for these proteins in the same cortical region in subjects with schizophrenia. GAD67 mRNA expression is decreased, suggesting altered prefrontal GABA-mediated neurotransmission in schizophrenia. Furthermore, the expression of parvalbumin mRNA is decreased, whereas the expression of calretinin mRNA is unchanged. These findings, as a group, suggest that prefrontal GABA neurons regulating pyramidal neuron firing are more prominently affected in schizophrenia than are other subpopulations of GABA neurons. Dysregulation of pyramidal neuron firing may contribute to cognitive dysfunction in schizophrenia.Address reprint requests to Dr. Tamminga, UT Southwestern Medical Center, Department of Psychiatry, 5323 Harry Hines Blvd., #NC5.914, Dallas, TX 75390-9070; [email protected] (e-mail). Figure. GABA Neurons in the Human Prefrontal Cortex FiguresReferencesCited byDetailsCited ByUnique gene alterations are induced in FACS-purified Fos-positive neurons activated during cue-induced relapse to heroin seeking21 November 2012 | Journal of Neurochemistry, Vol. 124, No. 1Selective epigenetic alteration of layer I GABAergic neurons isolated from prefrontal cortex of schizophrenia patients using laser-assisted microdissection30 January 2007 | Molecular Psychiatry, Vol. 12, No. 4NeuroReport, Vol. 17, No. 6The Journal of Comparative Neurology, Vol. 490, No. 3 Volume 161Issue 10 October 2004Pages 1764-1764 Metrics PDF download History Published online 22 December 2014 Published in print 1 October 2004

Identification of estrogen-responsive genes in the GH3 cell line by cDNA microarray analysis

To identify estrogen-responsive genes in somatolactotrophic cells of the pituitary gland, a rat pituitary cell line GH3 was subjected to cDNA microarray analysis. GH3 cells respond to estrogen by growth as well as prolactin synthesis. RNAs extracted from GH3 cells treated with 17β-estradiol (E2) at 10 −9 M for 24 h were compared with the control samples. The effect of an antiestrogen ICI182780 was also examined. The array analysis indicated 26 genes to be up-regulated and only seven genes down-regulated by E2. Fourteen genes were further examined by real-time RT-PCR quantification and 10 were confirmed to be regulated by the hormone in a dose-dependent manner. Expression and regulation of these genes were then examined in the anterior pituitary glands of female F344 rats ovariectomized and/or treated with E2 and 8 out of 10 were again found to be up-regulated. Interestingly, two of the most estrogen-responsive genes in GH3 cells were strongly dependent on E2 in vivo. #1 was identified as calbindin-D9k mRNA, with 80- and 118-fold induction over the ovariectomized controls at 3 and 24 h, respectively, after E2 administration. #2 was found to be parvalbumin mRNA, with 30-fold increase at 24 h. Third was c- myc mRNA, with 4.5 times induction at 24 h. The levels were maintained after one month of chronic E2 treatment. Identification of these estrogen-responsive genes should contribute to understating of estrogen actions in the pituitary gland.

Parvalbumin expression in visual cortical interneurons depends on neuronal activity and TrkB ligands during an Early period of postnatal development.

The differentiation of cortical interneurons is controlled by environmental factors. Here, we describe the role of activity and neurotrophins in regulating parvalbumin (PARV) expression using organotypic cultures (OTC) of rat visual cortex as model system. In OTC, PARV expression was dramatically delayed. The organotypic proportion of approximately 6% PARV neurons was not established before 50-70 DIV, whereas in vivo all neurons are present until P20. Thalamic afferents increased cortical PARV mRNA in OTC, but not to the age-matched in vivo level. During the first 10 DIV, BDNF and NT-4 accelerated PARV mRNA expression in a Trk receptor and MEK2 dependent manner. The BDNF action required PI3 kinase signalling. PARV expression required activity. The proportion of neurons which managed to up-regulate PARV was inversely related to the duration of early transient periods of activity deprivation. Long-term activity-deprived OTC completely failed to up-regulate PARV mRNA. Both TrkB ligands failed to promote PARV expression in activity-deprived OTC. However, a few basket and chandelier neurons were observed, suggesting that the development of class-specific morphological features is activity-independent. Once established, PARV expression became resistant to late-onset activity deprivation. In conclusion, PARV expression depended on activity and TrkB ligands which appear to prime the PARV expression already before its developmental onset.

Gene Expression Deficits in a Subclass of GABA Neurons in the Prefrontal Cortex of Subjects with Schizophrenia

Markers of inhibitory neurotransmission are altered in the prefrontal cortex (PFC) of subjects with schizophrenia, and several lines of evidence suggest that these alterations may be most prominent in the subset of GABA-containing neurons that express the calcium-binding protein, parvalbumin (PV). To test this hypothesis, we evaluated the expression of mRNAs for PV, another calcium-binding protein, calretinin (CR), and glutamic acid decarboxylase (GAD67) in postmortem brain specimens from 15 pairs of subjects with schizophrenia and matched control subjects using single- and dual-label in situ hybridization. Signal intensity for PV mRNA expression in PFC area 9 was significantly decreased in the subjects with schizophrenia, predominantly in layers III and IV. Analysis at the cellular level revealed that this decrease was attributable principally to a reduction in PV mRNA expression per neuron rather than by a decreased density of PV mRNA-positive neurons. In contrast, the same measures of CR mRNA expression were not altered in schizophrenia. These findings were confirmed by findings from cDNA microarray studies using different probes. Across the subjects with schizophrenia, the decrease in neuronal PV mRNA expression was highly associated (r = 0.84) with the decrease in the density of neurons containing detectable levels of GAD67 mRNA. Furthermore, simultaneous detection of PV and GAD67 mRNAs revealed that in subjects with schizophrenia only 55% of PV mRNA-positive neurons had detectable levels of GAD67 mRNA. Given the critical role that PV-containing GABA neurons appear to play in regulating the cognitive functions mediated by the PFC, the selective alterations in gene expression in these neurons may contribute to the cognitive deficits characteristic of schizophrenia.

Rat hippocampal GABAergic molecular markers are differentially affected by ageing.

We previously reported that the pharmacological properties of the hippocampal GABAA receptor and the expression of several subunits are modified during normal ageing. However, correlation between these post-synaptic modifications and pre-synaptic deficits were not determined. To address this issue, we have analysed the mRNA levels of several GABAergic molecular markers in young and old rat hippocampus, including glutamic acid decarboxylase enzymes, parvalbumin, calretinin, somatostatin, neuropeptide Y and vasoactive intestinal peptide (VIP). There was a differential age-related decrease in these interneuronal mRNAs that was inversely correlated with up-regulation of the alpha1 GABA receptor subunit. Somatostatin and neuropeptide Y mRNAs were most frequently affected (75% of the animals), then calretinin and VIP mRNAs (50% of the animals), and parvalbumin mRNA (25% of the animals) in the aged hippocampus. This selective vulnerability was well correlated at the protein/cellular level as analysed by immunocytochemistry. Somatostatin interneurones, which mostly innervate principal cell distal dendrites, were more vulnerable than calretinin interneurones, which target other interneurones. Parvalbumin interneurones, which mostly innervate perisomatic domains of principal cells, were preserved. This age-dependent differential reduction of specific hippocampal inteneuronal subpopulations might produce functional alterations in the GABAergic tone which might be compensated, at the post-synaptic level, by up-regulation of the expression of the alpha1 GABAA receptor subunit.

Induction of metabolic hypofunction and neurochemical deficits after chronic intermittent exposure to phencyclidine: differential modulation by antipsychotic drugs.

Numerous human imaging studies have revealed an absolute or relative metabolic hypofunction within the prefrontal cortex, thalamus and temporal lobes of schizophrenic patients. The former deficit correlates with cognitive deficits and negative symptoms, whereas the latter correlates with positive symptomologies. There is also general consensus that schizophrenia is associated with decreased parvalbumin expression in the prefrontal cortex. Since the drug phencyclidine can induce a psychosis resembling schizophrenia in humans, we have examined whether repeated phencyclidine (PCP) treatment to rats could produce similar metabolic and neurochemical deficits to those occurring in schizophrenia and whether these deficits could be modulated by antipsychotic drugs. We demonstrate here that chronic intermittent exposure to PCP (2.58 mg kg(-1) i.p.) elicits a metabolic hypofunction, as demonstrated by reductions in the rates of glucose utilization, within the prefrontal cortex, reticular nucleus of thalamus and auditory system, key structures displaying similar changes in schizophrenia. Moreover, chronic PCP treatment according to this regime also decreases parvalbumin mRNA expression in the rat prefrontal cortex and reticular nucleus of the thalamus. Chronic coadministration of haloperidol (1 mg kg(-1) day(-1)) or clozapine (20 mg kg(-1) day(-1)) with PCP did not modulate PCP-induced reductions in metabolic activity in the rat prefrontal cortex, but reversed deficits in the structures of the auditory system. Clozapine, but not haloperidol, reversed PCP-induced decreases in parvalbumin expression in prefrontal cortex GABAergic interneurons, whereas both drugs reversed the deficits in the reticular nucleus of the thalamus. These data provide important new information, which strengthen the validity of chronic PCP as a useful animal model of schizophrenia, when administered according to this protocol. Furthermore, we propose that reversal of PCP-induced reductions in parvalbumin expression in the prefrontal cortex may be a potential marker of atypical antipsychotic activity in relation to amelioration of cognitive deficits and negative symptoms of schizophrenia.

Region‐specific and Age‐related Decrease of Parvalbumin Gene Expression in the Prefrontal Cortex of Elderly Patients with Schizophrenia

Background: Multiple studies on schizophrenia have suggested a dysfunction of γ‐aminobutyric acid (GABA) transmission in the prefrontal cortex (PFC) and some vulnerability of the central nervous system to the aging process. Since one of the calcium‐binding proteins, parvalbumin (PV) is a useful marker for a subpopulation of GABAergic local circuit neurons, we determined the PV gene expression in the PFC in schizophrenic brains to study a possible involvement of GABAergic system and its vulnerability, if any, to the aging process.Methods: We attempted a detailed in situ hybridization to determine the PV gene expression throughout the three PFC subregions (Brodmann areas; BAs 9, 10, and 11) from six elderly patients with schizophrenia and five age‐matched normal individuals.Results: The regional levels of PV messenger RNA (mRNA) were significantly decreased in BAs 9 and 10 of schizophrenics compared with controls. The cellular levels were significantly decreased in layers III, IV, and V in BAs 9 and 10 of schizophrenics. However, in BA 11 of schizophrenics, the cellular level was significantly decreased in layer in alone. There were significant reverse correlations between the PV mRNA levels in those areas and the age at death in the schizophrenic group, but not in the controls.Conclusion: The present results not only provide further evidence of a disturbance in GABA transmission in the PFC of schizophrenics, but also suggest that such dysfunction may be region‐specific and vulnerable to the aging process.

Granule cell hyperexcitability in the early post-traumatic rat dentate gyrus: the 'irritable mossy cell' hypothesis.

1. Cytochemical and in vitro whole-cell patch clamp techniques were used to investigate granule cell hyperexcitability in the dentate gyrus 1 week after fluid percussion head trauma. 2. The percentage decrease in the number of hilar interneurones labelled with either GAD67 or parvalbumin mRNA probes following trauma was not different from the decrease in the total population of hilar cells, indicating no preferential survival of interneurones with respect to the non-GABAergic hilar cells, i.e. the mossy cells. 3. Dentate granule cells following trauma showed enhanced action potential discharges, and longer-lasting depolarizations, in response to perforant path stimulation, in the presence of the GABAA receptor antagonist bicuculline. 4. There was no post-traumatic alteration in the perforant path-evoked monosynaptic excitatory postsynaptic currents (EPSCs), or in the intrinsic properties of granule cells. However, after trauma, the monosynaptic EPSC was followed by late, polysynaptic EPSCs, which were not present in controls. 5. The late EPSCs in granule cells from fluid percussion-injured rats were not blocked by the NMDA receptor antagonist 2-amino-5-phosphonovaleric acid (APV), but were eliminated by both the non-NMDA glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and the AMPA receptor antagonist GYKI 53655. 6. In addition, the late EPSCs were not present in low (0.5 mM) extracellular calcium, and they were also eliminated by the removal of the dentate hilus from the slice. 7. Mossy hilar cells in the traumatic dentate gyrus responded with significantly enhanced, prolonged trains of action potential discharges to perforant path stimulation. 8. These data indicate that surviving mossy cells play a crucial role in the hyperexcitable responses of the post-traumatic dentate gyrus.

Postnatal expression pattern of calcium-binding proteins in organotypic thalamic cultures and in the dorsal thalamus in vivo

The present study describes the postnatal expression of calbindin, calretinin and parvalbumin and glutamic acid decarboxylase (GAD) and microtubule-associated protein 2 (MAP2) in organotypic monocultures of rat dorsal thalamus compared to the thalamus in vivo. Cultures were maintained for up to 7 weeks. Cortex-conditioned medium improved the survival of thalamic cultures. MAP2-immunoreactive material was present in somata and dendrites of small and large-sized neurons throughout the cultures. Parvalbumin immunoreactivity was present in larger multipolar or bitufted neurons along the edge of a culture. These neurons also displayed strong parvalbumin mRNA and GAD mRNA expression, and GABA immunoreactivity. They likely corresponded to cells of the nucleus reticularis thalami. Parvalbumin mRNA, but neither parvalbumin protein nor GAD mRNA, was expressed in neurons with large somata within the explant. They likely represented relay cells. GAD mRNA, but not parvalbumin mRNA, was expressed in small neurons within the explants. Small neurons also displayed calbindin- and calretinin-immunoreactivity. The small neurons likely represented local circuit neurons. The time course of expression of the calcium-binding proteins revealed that all were present at birth with the predicted molecular weights. A low, but constant parvalbumin expression was observed in vitro without the developmental increase seen in vivo, which most likely represented parvalbumin from afferent sources. In contrast, the explantation transiently downregulated the calretinin and calbindin expression, but the neurons recovered the expression after 14 and 21 days, respectively. In conclusion, thalamic monocultures older than three weeks represent a stable neuronal network containing well differentiated neurons of the nucleus reticularis thalami, relay cells and local circuit neurons.

Calbindin D28K and parvalbumin gene expression in rat embryonic ventral forebrain grafts.

The present study characterizes expression of calbindin D28K (CB-D28K) and parvalbumin (PV) in ventral forebrain (VFB) grafts placed in the neocortex of adult rats bearing quisqualic acid lesions to the nucleus basalis magnocellularis. Three to nine months after transplantation surgery, rats were killed for in situ hybridization with probes to CB-D28K or PV and for immunohistochemistry with antibodies to CB-D28K or PV. In addition, an antibody to choline acetyltransferase (ChAT) was used to characterize the cholinergic component in the graft and an antibody to tyrosine hydroxylase (TH) to explore catecholaminergic innervation of the graft. Quantitative analysis of CB-D28K and PV messenger ribonucleic acid (mRNA) was based on counts of silver grains generated by emulsion autoradiography. Cells expressing CB-D28K mRNA were significantly larger than such cells in the adult VFB and the mean number of silver grains per cell was significantly greater than to such cells in the adult VFB. The level of CB-D28K mRNA expression as calculated by ratio of silver grains per unit area was also significantly increased. Quantification of PV mRNA showed no significant differences between the cells in the graft and in the adult VFB. In order to begin to interpret these findings, a comparison was made with such cells in the VFB of developing rats. Brain sections were sampled from embryonic day 17 and postnatal days 1, 5, 12, 19 and adult (6-12 months of age). Cells expressing CB-D28K mRNA were detected in ventral forebrain from postnatal day 5 and cells expressing PV mRNA were detected in ventral forebrain from postnatal day 19. In the course of normal development of the ventral forebrain, no CB-D28K cells were found that were as large or expressed such high levels of CB-D28K mRNA as observed in the grafts. We conclude that changes in grafted cells expressing CB-D28K do not reflect an arrest of developmental processes. TH immunohistochemistry revealed lack of catecholaminergic innervation of the graft, whereas adult mediolateral septal cells that express CB-D28K receive such innervation in addition to other neurotransmitter inputs. Imbalance in neurotransmitter inputs to grafted cells expressing CB-D28K is discussed as a possible factor in their increased size and gene expression.