Evaluation of the COVID-19 pandemic effect on the development of somatic symptoms in patients with mood disorders: a case-control study.

Somatic symptoms are one of the most common complaints among patients with psychiatric disorders and are considered as one of the most common psychiatric disorders in the new coronavirus pandemic. This study aimed to evaluate the effect of the COVID-19 pandemic on the physical symptoms in patients with mood disorders and compare it with healthy individuals. In this case-control study, 67 patients with mood disorders were referred to the psychiatric clinic of 5 Azar Hospital in Gorgan, who met the inclusion criteria, and 68 healthy individuals as control group were entered into the study. For all participants after informed consent, a demographic information questionnaire was completed along with Screening for Somatic Symptoms-7 (SOMS7) and Patient Health Questionnaire-15 (PHQ-15), and the data were analysed by SPSS software version 25. The mean score obtained for the SOMS-7 questionnaire for the group of patients with mood disorders and the control group was 32.37 ± 8.19 and 35.42 ± 11.3, respectively. The mean obtained for the PHQ-15 questionnaire for the mood disorders group and the control group was 8.56 ± 5.93 and 5.86 ± 4.63, respectively. In the mood disorder group, 26.9% of patients had no risk for physical symptoms, 31.3% of patients had a low risk, 25.4% of patients had a moderate risk, and 16.4% of patients had a high risk for physical symptoms. The statistical test showed that although the risk of physical symptoms was high in both groups, this rate was higher in the group with mood disorders, and there is a significant difference between the two groups (P < 0.05). The results also showed a significant and direct relationship between the two questionnaires (P < 0.05). According to the results, although the prevalence of somatic symptoms increased in both groups, the prevalence of somatic symptoms is significantly higher in the mood disorder group.

Glutamatergic plasticity in medial prefrontal cortex and ventral tegmental area following extended-access cocaine self-administration.

Glutamate signaling in prefrontal cortex and ventral tegmental area plays an important role in the molecular and behavioral plasticity associated with addiction to drugs of abuse. The current study investigated the expression and postsynaptic density redistribution of glutamate receptors and synaptic scaffolding proteins in dorsomedial and ventromedial prefrontal cortex and ventral tegmental area after cocaine self-administration. After 14 days of extended-access (6h/day) cocaine self-administration, rats were exposed to one of three withdrawal regimen for 10 days. Animals either stayed in home cages (Home), returned to self-administration boxes with the levers withdrawn (Box), or underwent extinction training (Extinction). Extinction training was associated with significant glutamatergic plasticity. In dorsomedial prefrontal cortex of the Extinction group, there was an increase in postsynaptic density GluR1, PSD95, and actin proteins; while postsynaptic density mGluR5 protein decreased and there was no change in NMDAR1, Homer1b/c, or PICK1 proteins. These changes were not observed in ventromedial prefrontal cortex or ventral tegmental area. In ventral tegmental area, Extinction training reversed the decreased postsynaptic density NMDAR1 protein in the Home and Box withdrawal groups. These data suggest that extinction of drug seeking is associated with selective glutamatergic plasticity in prefrontal cortex and ventral tegmental area that include modulation of receptor trafficking to postsynaptic density.

Region-specific alterations in glutamate receptor expression and subcellular distribution following extinction of cocaine self-administration.

A role for glutamatergic signaling in the nucleus accumbens (NA) in both the expression and extinction of cocaine seeking has been suggested. The effects of extinction following cocaine self-administration on the expression and synaptosomal distribution of GluR1 and NMDAR1 glutamate receptor subunits in the NA shell and core and the dorsolateral striatum were examined. Rats self-administered cocaine or had access to saline for 14 days followed by a period of extinction training, home-cage exposure, or placement in the self-administration chambers with levers retracted in the absence of discrete cues. Self-administration followed by home-cage exposure reduced GluR1 expression in the NA shell and NMDAR1 expression in the dorsolateral striatum without affecting expression in the NA core. These effects were not observed following extinction. Extinction training increased synaptosomal GluR1 in the NA shell and core and NMDAR1 in the dorsolateral striatum while decreasing synaptosomal NMDAR1 in the shell. Extinction but not home-cage exposure was associated with altered expression and synaptosomal content of the scaffolding proteins PICK1 and PSD95.Following extinction, synaptosomal PICK1 decreased in the dorsolateral striatum while total PICK1 expression was increased in the shell. The synaptosomal PSD95 was decreased in the NA shell, while total PSD95 expression was increased in the core. These data suggest that extinguished cocaine seeking is associated with changes in GluR1 and NMDAR1 expression and subcellular distribution that are region-specific and consist of both a reversal of cocaine-induced adaptations and emergent extinction-related alterations that include receptor subunit redistribution and may involve alterations in scaffolding proteins.

Locomotor sensitization to cocaine is associated with distinct pattern of glutamate receptor trafficking to the postsynaptic density in prefrontal cortex: early versus late withdrawal effects.

Glutamatergic neurotransmission plays an important role in the behavioral and molecular plasticity observed in cocaine mediated locomotor sensitization. Recent studies show that glutamatergic signaling is regulated by receptor trafficking, synaptic localization, and association with scaffolding proteins. The trafficking of the glutamate receptors was investigated in the dorsal and ventral prefrontal cortex at 1 and 21 days after repeated cocaine administration which produced robust locomotor sensitization. A subcellular fractionation technique was used to isolate the cellular synaptosomal fraction containing the postsynaptic density. At early withdrawal, the prefrontal cortex displayed a reduction in the synaptosomal content of the AMPA and NMDA receptor subunits. In contrast, after extended withdrawal, there was a significant increase in the trafficking of the receptors into the synaptosomal compartment. These changes were accompanied by corresponding trafficking of the postsynaptic glutamatergic scaffolding proteins. Thus, enhanced trafficking of glutamate receptors from cytosolic to synaptosomal compartment is associated with prolonged withdrawal from repeated exposure to cocaine and may have functional consequences for the synaptic and behavioral plasticity.

Neuroadaptations in the cellular and postsynaptic group 1 metabotropic glutamate receptor mGluR5 and Homer proteins following extinction of cocaine self-administration.

This study examined the role of group1 metabotropic glutamate receptor mGluR5 and associated postsynaptic scaffolding protein Homer1b/c in behavioral plasticity after three withdrawal treatments from cocaine self-administration. Rats self-administered cocaine or saline for 14 days followed by a withdrawal period during which rats underwent extinction training, remained in their home cages, or were placed in the self-administration chambers in the absence of extinction. Subsequently, the tissue level and distribution of proteins in the synaptosomal fraction associated with the postsynaptic density were examined. Cocaine self-administration followed by home cage exposure reduced the mGluR5 protein in nucleus accumbens (NA) shell and dorsolateral striatum. While extinction training reduced mGluR5 protein in NAshell, NAcore and dorsolateral striatum did not display any change. The scaffolding protein PSD95 increased in NAcore of the extinguished animals. Extinction of drug seeking was associated with a significant decrease in the synaptosomal mGluR5 protein in NAshell and an increase in dorsolateral striatum, while that of NAcore was not modified. Interestingly, both Homer1b/c and PSD95 scaffolding proteins were decreased in the synaptosomal fraction after extinction training in NAshell but not NAcore. Extinguished drug-seeking behavior was also associated with an increase in the synaptosomal actin proteins in dorsolateral striatum. Therefore, extinction of cocaine seeking is associated with neuroadaptations in mGluR5 expression and distribution that are region-specific and consist of extinction-induced reversal of cocaine-induced adaptations as well as emergent extinction-induced alterations. Concurrent plasticity in the scaffolding proteins further suggests that mGluR5 receptor neuroadaptations may have implications for synaptic function.

Behavioral sensitization to cocaine is associated with increased glutamate receptor trafficking to the postsynaptic density after extended withdrawal period.

Glutamatergic signaling plays an important role in the behavioral and molecular plasticity observed in behavioral sensitization to cocaine. Redistribution of the glutamate receptors in the synaptosomal membrane fraction was investigated in the nucleus accumbens, dorsolateral striatum, and ventral tegmental area at 1 or 21 days of withdrawal in behaviorally sensitized rats. At 1 day of withdrawal, there were no changes in either tissue level or redistribution of glutamate receptors in nucleus accumbens core and shell and ventral tegmental area. At 21 days of withdrawal, there was a decrease in the expression of mGluR2/3 protein in core and shell, an increase in GluR1 and a decrease in Homer1b/c proteins in the nucleus accumbens core tissue. In dorsolateral striatum, the tissue level of NMDAR2B protein was increased. Moreover, there was an augmented presence of AMPA (GluR1, GluR2), NMDA (NMDAR1, 2A, 2B), and group 1 metabotropic glutamate receptor (mGluR5) proteins in the synaptosomal fraction in core and shell of the nucleus accumbens. There was also an increase in synaptosomal mGluR2/3 protein in nucleus accumbens core. The redistribution of glutamate receptors was selective for nucleus accumbens since no changes were observed in the dorsolateral striatum and ventral tegmental area. While the tissue level of the Homer1b/c protein was selectively reduced in nucleus accumbens core, that of PSD95, PICK1, and actin was not changed in any of the brain regions examined. However, the synaptosomal membrane fraction level of Homer1b/c and PSD95 was increased in nucleus accumbens core and shell, with no changes in PICK1, and a decrease in actin protein. These observations suggest that significant redistribution of glutamate receptors and postsynaptic scaffolding proteins into synaptosomal membrane fraction is associated with withdrawal from behavioral sensitization to cocaine.

Cocaine activates Homer1 immediate early gene transcription in the mesocorticolimbic circuit: differential regulation by dopamine and glutamate signaling.

Homer proteins are intracellular scaffolding proteins that, among glutamate receptors, selectively bind to group1 metabotropic glutamate receptors and regulate their trafficking and intracellular signaling. Homer proteins have been implicated in synaptic and behavioral plasticity, including drug-seeking behavior after cocaine treatment. Homer1 gene activation leads to transcription of a variant mRNA (Homer1a), which functions as an immediate early gene. Homer1a competes with the constitutive Homer proteins (Homer1b/c/d, Homer2a/b, Homer3) for binding to group1 metabotropic glutamate and IP3 receptors. Binding of Homer1a to these proteins disrupts their association with the intracellular signaling scaffold and modulates receptor function. In this study, using RT-PCR, activation of Homer1a mRNA transcription in response to acute and repeated administration of cocaine was characterized in prefrontal cortex, nucleus accumbens, and ventral tegmental area, three mesocorticolimbic nuclei of the rat brain. Moreover, the dopaminergic and glutamatergic regulation of Homer1 gene activation by cocaine was investigated. Acute cocaine rapidly and transiently activated transcription of Homer1a mRNA in all three nuclei. However, repeated administration of cocaine was not effective in inducing the Homer1a mRNA transcription after various withdrawal times ranging from 2 h to 3 weeks. The acute cocaine-mediated activation of Homer1 gene was regulated by D1 but not D2 dopamine receptors. The blockade of AMPA or NMDA glutamate receptors did not prevent cocaine-mediated activation of Homer1 gene in the three mesocorticolimbic nuclei. These data indicate that acute administration of cocaine transiently activates Homer1 gene producing the immediate early gene Homer1a mRNA in the three mesocorticolimbic nuclei of the rat brain. Activation of Homer1 gene may contribute to the cocaine-mediated synaptic and behavioral plasticity.

Homer1 proteins and AMPA receptors modulate cocaine-induced behavioural plasticity.

Homer proteins form functional assemblies in the excitatory postsynaptic density, and withdrawal from repeated cocaine administration reduces the expression of Homer1b/c in the nucleus accumbens. To determine if the reduction in Homer1b/c may be contributing to cocaine-induced behavioural sensitization, antisense oligonucleotides were infused over two weeks into the nucleus accumbens of rats to reduce Homer1 gene expression by approximately 35%. Infusion of antisense sequences (AS1 and AS2) caused a sensitization-like augmentation in the motor response to acute cocaine administration in naive rats. One of the sequences (AS1) also prevented the development of sensitization to repeated cocaine treatment, while AS2 was without effect. A panel of immunoblots for other proteins in the excitatory postsynaptic density revealed that AS1, but not AS2 reduced the level of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor subunit GluR1 protein. This posed the possibility that altered AMPA signalling may mediate the inhibitory effect of AS1 on the development of sensitization. To examine this possibility, rats were pretreated in the accumbens with drugs to block AMPA/kainate, N-methyl-d-aspartate, group 1 metabotropic glutamate or dopamine receptors prior to each daily injection of cocaine. Only AMPA/kainate receptor blockade prevented the development of behavioural sensitization to cocaine. These data indicate that the expression of behavioural sensitization arises in part from a reduction in Homer1 gene products in the accumbens, while the development of sensitization requires stimulation of AMPA/kainate receptors.

Neuroadaptive changes in NMDAR1 gene expression after extinction of cocaine self-administration.

The aim of the present work was to study the time course effects in levels of mRNA encoding N-methyl-d-aspartate receptor subunit 1 (NMDAR1) after long-term cocaine self-administration (1 mg/kg/ injection) and its extinction using a yoked-box procedure. NMDAR1 content was measured by quantitative in situ hybridization histochemistry in prefrontal cortex, caudate-putamen, nucleus accumbens, olfactory tubercle, and piriform cortex immediately after cessation of the last session of cocaine self-administration (Day 0) and 1, 5, and 10 days after the extinction period. The results show that long-term cocaine self-administration and its extinction alter NMDAR1 gene expression in these forebrain regions, and that the changes depend upon the brain region examined and the type of cocaine administration (contingent, noncontingent, and saline). Compared to saline and noncontingent cocaine administration, contingent cocaine produced an up-regulation in NMDAR1 gene expression on Day 0 in all the brain regions analyzed. NMDAR1 levels of contingent animals decreased progressively in the absence of cocaine, and the decrement persisted 10 days after the extinction of cocaine self-administration behavior in all the forebrain areas, with the exception of olfactory tubercle. In contrast, noncontingent cocaine administration did not produce any change in NMDAR1 gene expression on Day 0, and extinction resulted in an increase of NMDAR1 mRNA content on Days 1 and 5 and returned to control (saline) values on Day 10. These results suggest that an interaction between environmental stimuli and the pharmacological action of cocaine during drug self-administration and its extinction may represent an important factor in the regulation of cocaine effects on NMDAR1 gene expression.

The monoamine neurons of the rat brain preferentially express a splice variant of alpha1B subunit of the N-type calcium channel.

The N-type voltage-dependent calcium channels play a significant role in neurotransmitter release. The alpha1B subunit of the N-type calcium channel functions as the primary subunit that forms the pore and contains the structural motifs that mediate the pharmacological and gating properties of the channel. We report on an isoform of the alpha1B subunit that is preferentially expressed by the monoaminergic neurons of the rat brain. This isoform contains a 21-amino acid cassette in the synprint site present in the cytoplasmic loop between domains IIS6 and IIIS1. RT-PCR of micropunched tissue was used to show preferential expression of this isoform in regions of the brain containing monoaminergic neurons and to a lesser extent in the cerebellum. Double-label in situ hybridization was used to show expression of this isoform mRNA in dopaminergic neurons of the ventral mesencephalon. The expression of two distinct N-type calcium channels containing these alpha1B subunit isoforms by the monoaminergic neurons may provide for synapse-specific regulation of neurotransmitter release.

Regional distribution and cellular localization of gamma-aminobutyric acid subtype 1 receptor mRNA in the rat brain.

The distribution of gamma-aminobutyric acid (GABA) receptor subtype B1 (GABA(B1)) mRNA-containing cells in the brain of adult rats was determined with in situ hybridization histochemistry. The vast majority of neurons expressed GABA(B1) receptor mRNA. However, there were nuclei of relative high density, and, in some nuclei, the majority of neurons did not express detectable levels of GABA(B1) receptor transcripts. Areas where the majority of neurons expressed a high density of mRNA included the medial habenula; the septohippocampal, periventricular, suprachiasmatic, and supraoptic nuclei; Purkinje cells in the cerebellum; and pyramidal and granule cells of the hippocampus and dentate gyrus, respectively. Also, brainstem nuclei containing monoaminergic neurons and neurons in the thalamic motor nuclei contained relatively high levels of expression. mRNA was low or absent in neuronal populations in regions with well-developed cytoarchitecture, such as the stratum radiatum and stratum oriens of the hippocampus, the molecular and granular layers of the cerebellum, and the molecular layer of the cortex. Low expression was observed also in many extrapyramidal nuclei, such as the globus and ventral pallidum and the substantia nigra, pars reticulata. Expression also was low in the reticular thalamic nucleus and zona incerta. Neurons lacking detectable GABA(B1) receptor mRNA were generally in nuclei that contained largely GABAergic neurons.

The regulation of dopamine transmission by metabotropic glutamate receptors.

Receptor subtype nonselective metabotropic glutamate receptor (mGluR) agonists have been shown to regulate the release of dopamine. The eight mGluR subtypes have been pharmacologically categorized into three groups, and the present study used in vivo microdialysis to examine the capacity of mGluR subgroup-selective drugs to modulate the extracellular levels of dopamine in the nucleus accumbens. By administering the drugs in the dialysis buffer, it was found that the group 3 mGluR agonist L-amino-4-phosphonobutyrate produced a dose-dependent reduction in extracellular dopamine, whereas the group 1 agonist 3,5-dihydroxyphenylglycine was ineffective. The group 2 agonist (2S,1'R,2'R,3'R)-2-(2, 3-dicarboxycyclopropyl)glycine produced a reduction that was biphasic with respect to dose. The group 2/3 antagonist alpha-methyl-4-phosphnophenylglycine elicited a dose-dependent increase in extracellular dopamine that was antagonized by coperfusion with either the L-type calcium channel blocker diltiazem or the group 3 agonist L-amino-4-phosphonobutyrate. These data demonstrate that group 3 and to a lesser extent group 2 mGluR may presynaptically regulate dopamine release or reuptake. Moreover, there exists significant in vivo glutamatergic tone on group 2/3 mGluRs to suppress extracellular dopamine levels.

Neuroadaptations in ionotropic and metabotropic glutamate receptor mRNA produced by cocaine treatment.

The expression of glutamate receptor/subunit mRNAs was examined 3 weeks after discontinuing 1 week of daily injections of saline or cocaine. The level of mRNA for GluR1-4, NMDAR1, and mGluR5 receptors was measured with in situ hybridization and RT-PCR. In nucleus accumbens, acute cocaine treatment significantly reduced the mRNA level for GluR3, GluR4, and NMDAR1 subunits, whereas repeated cocaine reduced the level for GluR3 mRNA. Acute cocaine treatment also reduced the NMDAR1 mRNA level in dorsolateral striatum and ventral tegmental area. In prefrontal cortex, repeated cocaine treatment significantly increased the level of GluR2 mRNA. The GluR2 mRNA level was not changed by acute or repeated cocaine in any other brain regions examined. Repeated cocaine treatment also significantly increased mGluR5 mRNA levels in nucleus accumbens shell and dorsolateral striatum. Functional properties of the ionotropic glutamate receptors are determined by subunit composition. In addition, metabotropic glutamate receptors can modulate synaptic transmission and the response to stimulation of ionotropic receptors. Thus, the observed changes in levels of AMPA and NMDA receptor subunits and the mGluR5 metabotropic receptor may alter excitatory neurotransmission in the mesocorticolimbic dopamine system, which could play a significant role in the enduring biochemical and behavioral effects of cocaine.

Expression of glutamate receptor subunit/subtype messenger RNAS for NMDAR1, GLuR1, GLuR2 and mGLuR5 by accumbal projection neurons.

Nucleus accumbens neurons are the targets of glutamatergic inputs. By coupling in situ hybridization for glutamate receptor mRNAs with retrograde transport of Fluoro-Gold, the present study examined the relationship between the distribution patterns of glutamate receptor subtypes/subunits and the output pathways of the nucleus accumbens to the ventral pallidum and ventral tegmental area. Following iontophoretic deposits of Fluoro-Gold into the ventral pallidum, neurons in both the nucleus accumbens shell and core were retrogradely labeled. A high percentage of accumbens neurons retrogradely labeled from the ventral pallidum were double-labeled for mRNAs encoding for mGluR5 (82+/-4.1%), NMDAR1 (71+/-3.5%), GluR1 (70+/-6.1%) and GluR2 (76+/-3.6%). No significant difference in the proportion of double-labeled neurons between the core and shell was observed. Following the deposit of Fluoro-Gold into the ventral tegmental area, only the accumbens shell neurons were retrogradely labeled. The proportion of neurons expressing NMDAR1, GluR1 and GluR2 were somewhat less in the projection to the ventral tegmental area compared to the ventral pallidum since approximately 60% of the neurons retrogradely-labeled from the ventral tegmental area expressed these transcripts. In contrast to the high proportion of mGluR5-containing neurons in the nucleus accumbens innervating the ventral pallidum, only half of the neurons projecting to the ventral tegmental area expressed mGluR5. These data show that accumbens neurons innervating the ventral pallidum and ventral tegmental area differ in the relative proportion of expressed mRNA encoding mGluR5, implying differential postsynaptic impact by glutamate transmission on neurons contributing to the two major efferent pathways of the nucleus accumbens.

Role of transforming growth factor (TGF)-beta Type I and TGF-beta type II receptors in the TGF-beta1-regulated gene expression in pituitary prolactin-secreting lactotropes.

Transforming growth factor beta1 (TGF-beta1) inhibits pituitary lactotrope proliferation and secretion of PRL in an autocrine/paracrine manner. In this study, the role of TGF-beta1 type I (TbetaR-I) and TGF-beta type II (TbetaR-II) receptors in TGF-beta1-regulated gene expression in lactotropes was determined using anterior pituitary cells known to be responsive to TGF-beta1 growth inhibition and using a transformed PR1 cell line known to be nonresponsive to TGF-beta1 growth inhibition. Treatment with TGF-beta1 inhibited cell proliferation and decreased PRL mRNA levels in anterior pituitary cells, but in PR-1 cells, the treatment caused only decreased PRL mRNA levels. Affinity labeling of TGF-beta binding proteins indicated that anterior pituitary cells contain several TGF-beta-binding protein complexes, including the 65 kDa size TbetaR-I and 95 kDa size TbetaR-II. In the PR1 cells, the major complex found was similar to the 65 kDa size of TbetaR-I. Immunocytochemistry identified TbetaR-I and TbetaR-II receptor proteins in lactotropes but detected primarily TbetaR-I receptor protein in PR1 cells. RT-PCR detection of TbetaR-I and TbetaR-II mRNA identified both receptor mRNA transcripts in anterior pituitary cells and in PR1 cells but the levels of TbetaR-II and TbetaR-I mRNA transcripts in PR1 cells was much lower than that in anterior pituitary cells. Determination of the TGF-beta1 gene responses in PR1 cells following TbetaR-I and TbetaR-II gene transfection indicated that PR1 cells transactivate transcription of the TGF-beta-responsive p3TP-Lux reporter in the absence of cotransfected TbetaR-II receptor. The introduction of the TbetaR-II receptor alone or in combination with TbetaR-I confer ligand-independent reporter transactivation in these cells. When only TbetaR-I was introduced along with reporter, a ligand-dependent transactivation was observed. These data suggest for the first time that the TGF-beta1-mediated transcriptional activation response can be distinguished from the growth response in lactotropes. Furthermore, the TGF-beta1 gene-transcription response is less dependent on TbetaR-II receptor expression than is the TGF-beta1 growth-inhibitory response.

Expression of D1 receptor, D2 receptor, substance P and enkephalin messenger RNAs in the neurons projecting from the nucleus accumbens.

In situ hybridization was combined with FluoroGold retrograde labelling to determine the distribution of messenger RNAs for the D1 dopamine receptor, D2 dopamine receptor, beta-preprotachykinin or preproenkephalin in the neurons projecting from the nucleus accumbens to the ventral pallidum and the ventral tegmental area. Neurons were quantified in both the core and the shell of the nucleus accumbens to estimate the proportion of neurons projecting to the ventral pallidum or ventral tegmental area that contain transcripts for D1 receptors, D2 receptors, beta-preprotachykinin or preproenkephalin. Following the deposition of FluoroGold into the central ventral pallidum, both the core and the shell of the nucleus accumbens were retrogradely labelled, while deposits into the ventral tegmental area selectively labelled cells in the shell. A high percentage of nucleus accumbens neurons innervating the ventral tegmental area expressed messenger RNAs for D1 receptors (72%) and beta-preprotachykinin (62%), while less than 3% of the neurons contained messenger RNAs for preproenkephalin or D2 receptors. The neurons projecting to the ventral pallidum did not show the discrete distribution of transcripts as was observed in the accumbens-ventral tegmental area projection. Preproenkephalin messenger RNA was identified in 46% of the neurons innervating the ventral pallidum, and D2 receptor messenger RNA was found in approximately 40% of the cells. A large minority of neurons projecting from the nucleus accumbens to the ventral pallidum also expressed messenger RNAs for D1 receptors (37%) and beta-preprotachykinin (35%). While a higher percentage of D1 receptor, and beta-preprotachykinin messenger RNA expressing cells were located in the shell than in the core of the nucleus accumbens, the percentage tended to be higher in the core for cells expressing D2 receptors or preproenkephalin messenger RNA. These data indicate that messenger RNAs for D2 receptors and enkephalin are selectively expressed in the accumbens-pallidal projection while transcripts encoding D1 receptors and substance P are contained in the efferent projections to both the ventral pallidum and ventral tegmental area. The presence of D1 receptor and beta-preprotachykinin messenger RNAs in both mesencephalic and pallidal projections contrasts output from the striatum where the expression of D1 receptor and beta-preprotachykinin messenger RNAs is primarily restricted to the mesencephalic projection.

Multiplicity of glutamate receptor subunits in single striatal neurons: an RNA amplification study.

The RNA amplification technique was used to examine the pattern of coexpression of mRNAs encoding 16 subtypes/subunits of the glutamate receptor (GluR) in acutely dissociated neurons from adult rat striata. THe signal intensity for each mRNA varied within single neurons, but the general pattern of low versus high expression signals was similar among neurons, except for the GluR4 subunit of the (+/-)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. The mRNAs for GluR1-3 subunits of the AMPA receptor were present in all cells, with the signal intensity of GluR1 mRNAs usually the lowest. The kainate receptor subunit mRNAs (GluR5-7) were present in most neurons, and the signal intensity for GluR6 mRNA was the highest. The signals for N-methyl-D-aspartate (NMDA)R1 and NMDAR2B mRNAs were high in most neurons; however, NMDAR2A and NMDAR2C mRNAs gave low or undetectable signals. For mRNAs encoding metabotropic GluRs (mGluRs), signals for mGluR1, mGluR2, and mGluR3 mRNAs were low or undetectable, whereas mGluR4 and mGluR5 mRNA signals were high in most neurons. In most cases (12 of 16 mRNAs), the results agreed with data from in situ hybridization experiments in which individual mRNAs were examined. All neurons expressed subtypes/subunits mRNAs for all four types of GluRs; however, there were differences in the relative intensity of the mRNA signals detected in individual cells, suggesting that these receptors could exist in various combinations within individual neurons and thus confer synapse-specific function for information processing in the striatum.

Real-time monitoring of electrically stimulated norepinephrine release in rat thalamus: I. Resolution of transmitter and metabolite signal components.

Electrical stimulation of an ascending path of the locus ceruleus-norepinephrine system was used to elicit release of norepinephrine at noradrenergic terminal fields of the rat thalamus. Overflow into the extracellular fluid space was measured by fast in vivo chronoamperometry. At pretreated carbon fibers, the electrochemical signal consists of a sharp peak of approximately 20-30 s duration followed by a slower, plateau-like decay to baseline. The peak, characterized by a variety of pharmacological manipulations and dialysis perfusion, is primarily due to norepinephrine. The plateau was shown to correspond to metabolite efflux of 3,4-dihydroxy-phenylacetic acid. By varying the degree of electrochemical pretreatment, the response time and sensitivity of the fibers can be tuned to follow the entire signal or to select the separate components for detailed evaluation. This approach can be used to provide new information on the spatial and temporal characteristics of stimulated neurotransmitter release.