Abnormal Vasculature Development in Zebrafish Embryos with Reduced Expression of Pantothenate Kinase 2 Gene.

Mutations in pank2 gene encoding pantothenate kinase 2 determine a pantothenate kinase-associated neurodegeneration, a rare disorder characterized by iron deposition in the globus pallidus. To extend our previous work, we performed microinjections of a new pank2-specific morpholino to zebrafish embryos and thoroughly analyzed vasculature development. Vessels development was severely perturbed in the head, trunk, and tail, where blood accumulation was remarkable and associated with dilation of the posterior cardinal vein. This phenotype was specific as confirmed by p53 expression analysis and injection of the same morpholino in pank2-mutant embryos. We can conclude that pank2 gene is involved in vasculature development in zebrafish embryos. The comprehension of the underlining mechanisms could be of relevance for understanding of pantothenate kinase-associated neurodegeneration.

Thrombin-induced miRNA-24-1-5p upregulation promotes angiogenesis by targeting prolyl hydroxylase domain 1 in intracerebral hemorrhagic rats.

OBJECTIVE: Thrombin is a unique factor that triggers post-intracerebral hemorrhage (ICH) angiogenesis by increasing hypoxia-inducible factor-1α (HIF-1α) at the protein level. However, HIF-1α mRNA remains unchanged. MicroRNAs (miRNAs) mediate posttranscriptional regulation by suppressing protein translation from mRNAs. This study aimed to determine if miRNAs might be involved in thrombin-induced angiogenesis after ICH by targeting HIF-1α or its upstream prolyl hydroxylase domains (PHDs). METHODS: The study was divided into two parts. In part 1, rats received an injection of thrombin into the right globus pallidus. An miRNA array combined with miRNA target prediction, luciferase activity assay, and miRNA mimic/inhibitor transfection were used to identify candidate miRNAs and target genes. Part 2 included experiments 1 and 2. In experiment 1, rats were randomly divided into the sham group, ICH group, and ICH+hirudin-treated (thrombin inhibitor) group. In experiment 2, the rats were randomly divided into the sham group, ICH group, ICH+antagomir group, ICH+antagomir-control group, and ICH+vehicle group. Western blotting and quantitative real-time polymerase chain reaction were used to determine the expression of protein and miRNA, respectively. The coexpression of miR-24-1-5p (abbreviated to miR-24) and von Willebrand factor was detected by in situ hybridization and immunohistochemical analysis. The angiogenesis was evaluated by double-labeling immunofluorescence. Neurological function was evaluated by body weight, modified Neurological Severity Scores, and corner turn and foot-fault tests. RESULTS: In part 1, it was shown that miR-24, which is predicted to target PHD1, was upregulated (fold-change of 1.83) after thrombin infusion, and that the miR-24 mimic transfection decreased luciferase activity and downregulated PHD1 expression (p < 0.05). miR-24 inhibitor transfection increased PHD1 expression (p < 0.05). In part 2, it was shown that miR-24 was expressed in endothelial cells. The HIF-1α protein level and proliferating cell nuclear antigen-positive (PCNA+) nuclei in vessels were increased, while the PHD1 protein level was decreased after ICH, and these effects were reversed by hirudin (p < 0.05). The antagomiR-24-treated rats exhibited a markedly lower body weight and significantly poorer recovery from neurological deficit compared with those in ICH groups (p < 0.05). AntagomiR-24 intervention also led to lower miR-24 expression, a higher PHD1 protein level, and fewer PCNA+ nuclei in vessels compared with those in ICH groups (p < 0.05). CONCLUSIONS: The present study suggests that thrombin reduces HIF-1α degradation and initiates angiogenesis by increasing miR-24, which targets PHD1 after ICH.

Striatopallidal adenosine A2A receptors in the nucleus accumbens confer motivational control of goal-directed behavior.

The ability to learn the reward-value and action-outcome contingencies in dynamic environment is critical for flexible adaptive behavior and development of effective pharmacological control of goal-directed behaviors represents an important challenge for improving the deficits in goal-directed behavior which may underlie seemingly disparate symptoms across psychiatric disorders. Adenosine A2A receptor (A2AR) is emerging as a novel neuromodulatory target for controlling goal-directed behavior for its unique neuromodulatory features: the ability to integrate dopamine and glutamate signaling, the "brake" constraint of various cognitive processes and the balanced control of goal-directed and habit actions. However, the contribution and circuit mechanisms of the striatopallidal A2ARs in nucleus accumbens (NAc) to control of goal-directed behavior remain to be determined. Here, we employed newly developed opto-A2AR and the focal A2AR knockdown strategies to demonstrate the causal role of NAc A2AR in control of goal-directed behavior. Furthermore, we dissected out multiple distinct behavioral mechanisms underlying which NAc A2ARs control goal-directed behavior: (i) NAc A2ARs preferentially control goal-directed behavior at the expense of habit formation. (ii) NAc A2ARs modify the animals' sensitivity to the value of the reward without affecting the action-outcome contingency. (iii) A2AR antagonist KW6002 promotes instrumental actions by invigorating motivation. (iv) NAc A2ARs facilitate Pavlovian incentive value transferring to instrumental action. (v) NAc A2ARs control goal-directed behavior probably not through NAc-VP pathway. These insights into the behavioral and circuit mechanisms for NAc A2AR control of goal-directed behavior facilitate translational potential for A2AR antagonists in reversal of deficits in goal-directed decision-making associated with multiple neuropsychiatric disorders.

Effect of Anesthesia on Microelectrode Recordings during Deep Brain Stimulation Surgery in Tourette Syndrome Patients.

BACKGROUND: Deep brain stimulation (DBS) is an accepted treatment for patients with medication-resistant Tourette syndrome (TS). Sedation is commonly required during electrode implantation to attenuate anxiety, pain, and severe tics. Anesthetic agents potentially impair the quality of microelectrode recordings (MER). Little is known about the effect of these anesthetics on MER in patients with TS. We describe our experience with different sedative regimens on MER and tic severity in patients with TS. METHODS: The clinical records of all TS patients who underwent DBS surgery between 2010 and 2018 were reviewed. Demographic data, stimulation targets, anesthetic agents, perioperative complications, and MER from each hemisphere were collected and analyzed. Single-unit activity was identified by filtering spiking activity from broadband MER data and principal component analysis with K-means clustering. Vocal and motor tics which caused artifacts in the MER data were manually selected using visual and auditory inspection. RESULTS: Six patients underwent bilateral DBS electrode implantation. In all patients, the target was the anterior internal globus pallidus. Patient comfort and hemodynamic and respiratory stability were maintained with conscious sedation with one or more of the following anesthetic drugs: propofol, midazolam, remifentanil, clonidine, and dexmedetomidine. Good quality MER and clinical testing were obtained in 9 hemispheres of 6 patients. In 3 patients, MER quality was poor on one side. CONCLUSION: Cautiously applied sedative drugs can provide patient comfort, hemodynamic and respiratory stability, and suppress severe tics, with minimal interference with MER.

High Signal Intensity in the Dentate Nucleus and Globus Pallidus on Unenhanced T1-Weighted MR Images: Comparison between Gadobutrol and Linear Gadolinium-Based Contrast Agents.

BACKGROUND AND PURPOSE: In view of the recent observations that gadolinium deposits in brain tissue after intravenous injection, our aim of this study was to compare signal changes in the globus pallidus and dentate nucleus on unenhanced T1-weighted MR images in patients receiving serial doses of gadobutrol, a macrocyclic gadolinium-based contrast agent, with those seen in patients receiving linear gadolinium-based contrast agents. MATERIALS AND METHODS: This was a retrospective analysis of on-site patients with brain tumors. Fifty-nine patients received only gadobutrol, and 60 patients received only linear gadolinium-based contrast agents. Linear gadolinium-based contrast agents included gadoversetamide, gadobenate dimeglumine, and gadodiamide. T1 signal intensity in the globus pallidus, dentate nucleus, and pons was measured on the precontrast portions of patients' first and seventh brain MRIs. Ratios of signal intensity comparing the globus pallidus with the pons (globus pallidus/pons) and dentate nucleus with the pons (dentate nucleus/pons) were calculated. Changes in the above signal intensity ratios were compared within the gadobutrol and linear agent groups, as well as between groups. RESULTS: The dentate nucleus/pons signal ratio increased in the linear gadolinium-based contrast agent group (t = 4.215, P < .001), while no significant increase was seen in the gadobutrol group (t = -1.422, P = .08). The globus pallidus/pons ratios followed similarly, with an increase in the linear gadolinium-based contrast agent group (t = 2.931, P < .0001) and no significant change in those receiving gadobutrol (t = 0.684, P = .25). CONCLUSIONS: Successive doses of gadobutrol do not result in T1 shortening compared with changes seen in linear gadolinium-based contrast agents.

Development of High Signal Intensity within the Globus Pallidus and Dentate Nucleus following Multiple Administrations of Gadobenate Dimeglumine.

BACKGROUND AND PURPOSE: Previous studies have evaluated various gadolinium based contrast agents and their association with gadolinium retention, however, there is a discrepancy in the literature concerning the linear agent gadobenate dimeglumine. Our aim was to determine whether an association exists between the administration of gadobenate dimeglumine and the development of intrinsic T1-weighted signal in the dentate nucleus and globus pallidus. MATERIALS AND METHODS: In this single-center, retrospective study, the signal intensity of the globus pallidus, dentate nucleus, thalamus, and middle cerebellar peduncle was measured on unenhanced T1-weighted images in 29 adult patients who had undergone multiple contrast MRIs using exclusively gadobenate dimeglumine (mean, 10.1 ± 3.23 doses; range, 6-18 doses). Two neuroradiologists, blinded to the number of prior gadolinium-based contrast agent administrations, separately placed ROIs within the globi pallidi, thalami, dentate nuclei, and middle cerebellar peduncles on the last MR imaging examinations. The correlations between the globus pallidus:thalamus and the dentate nucleus:middle cerebellar peduncle signal intensity ratios with the number of gadolinium-based contrast agent administrations and cumulative dose were tested with either 1-tailed Pearson or Spearman correlations. A priori, P < .05 was considered statistically significant. RESULTS: Both the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the number of gadolinium-based contrast agent administrations (r = 0.39, P = .017, and r = 0.58, P = .001, respectively). Additionally, the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the cumulative dose of gadobenate dimeglumine (r = 0.48, P = .004, and r = 0.43, P = .009, respectively). Dentate nucleus hyperintensity was qualitatively present on the last MR imaging in 79.3%-86.2% of patients and in all patients who had received >10 doses. CONCLUSIONS: At high cumulative doses (commonly experienced by patients, for example, with neoplastic disease), gadobenate dimeglumine is associated with an increase in the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncles signal intensity ratios.

Presynaptic Dopamine D2 Receptors Modulate [3H]GABA Release at StriatoPallidal Terminals via Activation of PLC → IP3 → Calcineurin and Inhibition of AC → cAMP → PKA Signaling Cascades.

Striatal dopamine D2 receptors activate the PLC → IP3 → Calcineurin-signaling pathway to modulate the neural excitability of En+ Medium-sized Spiny GABAergic neurons (MSN) through the regulation of L-type Ca2+ channels. Presynaptic dopaminergic D2 receptors modulate GABA release at striatopallidal terminals through L-type Ca2+ channels as well, but their signaling pathway is still undetermined. Since D2 receptors are Gi/o-coupled and negatively modulate adenylyl cyclase (AC), we investigated whether presynaptic D2 receptors modulate GABA release through the same signaling cascade that controls excitability in the striatum or by the inhibition of AC and decreased PKA activity. Activation of D2 receptors stimulated formation of [3H]IP1 and decreased Forskolin-stimulated [3H]cAMP accumulation in synaptosomes from rat Globus Pallidus. D2 receptor activation with Quinpirole in the presence of L 745,870 decreased, in a dose-dependent manner, K+-induced [3H]GABA release in pallidal slices. The effect was prevented by the pharmacological blockade of Gi/o ßγ subunit effects with Gallein, PLC with U 73122, IP3 receptor activation with 4-APB, Calcineurin with FK506. In addition, when release was stimulated with Forskolin to activate AC, D2 receptors also decreased K+-induced [3H]GABA release, an effect occluded with the effect of the blockade of PKA with H89 or stimulation of release with the cAMP analog 8-Br-cAMP. These data indicate that D2 receptors modulate [3H]GABA release at striatopallidal terminals by activating the PLC → IP3 → Calcineurin-signaling cascade, the same one that modulates excitability in soma. Additionally, D2 receptors inhibit release when AC is active. Both mechanisms appear to converge to regulate the activity of presynaptic L-type Ca2+ channels.

T1 Shortening in the Globus Pallidus after Multiple Administrations of Gadobutrol: Assessment with a Multidynamic Multiecho Sequence.

Purpose To determine the association between the administration of the macrocyclic contrast medium gadobutrol and T1 relaxation time in the brains of patients with normal renal function by using multidynamic multiecho (MDME) magnetic resonance (MR) imaging sequences. Materials and Methods The institutional review board approved this retrospective study, and the need to obtain written informed consent was waived. This study included 46 patients (revealed by an electronic medical record search) who had received one or more gadobutrol injections and a maximum of one MR imaging contrast medium injection other than gadobutrol before MDME sequence acquisition. One radiologist performed quantitative analyses of regions of interest on quantitative T1 maps twice to cover the normal-appearing globus pallidus (GP), frontal white matter, frontal cortex, and thalamus. The number of administrations and the cumulative dose of gadobutrol, age, intervals between administrations, sex, and treatment were investigated. Univariable and multivariable linear regression analyses of the T1 values in four brain regions and the GP-to-thalamus signal intensity (SI) ratio were performed. P values of less than the Bonferroni-corrected value of .01 were considered to indicate significant differences. Results Intraobserver reproducibility was good to excellent (intraclass correlation coefficients, 0.62-0.81). Because of high multicollinearity between the number of gadobutrol administrations and accumulated dose (r = 0.96, P < .001), the number of gadobutrol administrations was considered in the regression analyses. T1 shortening in the GP was independently associated with the number of gadobutrol administrations (P = .002). T1 in the other brain regions and the GP-to-thalamus SI ratio were not significantly associated with the number of gadobutrol administrations (P > .01). Conclusion Multiple exposures to gadobutrol are associated with T1 shortening in the GP. © RSNA, 2017 Online supplemental material is available for this article.

Evaluation of Gadolinium Retention After Serial Administrations of a Macrocyclic Gadolinium-Based Contrast Agent (Gadobutrol): A Single-Institution Experience With 189 Patients.

OBJECTIVE: There has been controversy as to whether gadobutrol, one of the widely used macrocyclic gadolinium-based contrast agents, can lead to gadolinium retention after serial injections. Our aim was to validate whether serial administrations of gadobutrol can cause signal increase in the dentate nucleus (DN) and globus pallidus (GP) on unenhanced T1-weighted magnetic resonance (MR) images due to gadolinium retention. MATERIALS AND METHODS: A total of 189 patients who had undergone at least 2 contrast-enhanced MR scans using only gadobutrol between August 2009 and August 2016 were retrospectively included. The DN-to-pons and GP-to-thalamus signal intensity (SI) ratio differences on unenhanced T1-weighted MR images were calculated by subtracting the SI ratios at the first MR images from those at the last MR images. One-sample t tests were used to evaluate whether the SI ratio differences differed from 0. Linear regression and Pearson correlations were performed to assess correlations between SI ratio differences and various confounding variables, including the number of MR scans, mean time interval between MR scans, age, sex, history of radiation therapy or chemotherapy, and renal and liver functions. RESULTS: Patients underwent a mean of 5.9 ± 6.3 contrast-enhanced MR scans with a mean interval of 42.8 ± 49.5 weeks between the scans. Sixty-three patients underwent 6 or more MR scans, whereas 126 patients underwent fewer than 6 MR scans. Neither the DN-to-pons SI nor the GP-to-thalamus SI ratio differences differed significantly from 0, with mean values of -0.012 ± 0.115 (P = 0.148) and 0.012 ± 0.111 (P = 0.126), respectively. CONCLUSIONS: Serial administrations of gadobutrol did not result in signal increases in the DN or GP on unenhanced T1-weighted MR images due to gadolinium retention.

Chronic Nicotine Alters Corticostriatal Plasticity in the Striatopallidal Pathway Mediated By NR2B-Containing Silent Synapses.

Smoking is the leading cause of preventable death in the United States and success rates for quitting remain low. High relapse rates are attributed to pervasive nicotine-reinforced associative learning of incentive cues that is highly resistant to extinction. Why such learning is so persistent is poorly understood but may arise as a consequence of neuroadaptations in synaptic plasticity induced by chronic nicotine. We used whole-cell patch clamp recording to investigate the effect of chronic nicotine (cNIC) on synaptic plasticity in dopamine D2 receptor-expressing medium-spiny neurons in the indirect, striatopallidal pathway in dorsolateral striatum. Mice exposed to cNIC exhibited long-term potentiation in response to high-frequency stimulation instead of the expected depression. cNIC decreased baseline AMPA/NMDA ratio, arising from increased NMDA currents enriched in the NR2B subunit with a concomitant upregulation of NMDA-only, silent synapses. These data demonstrate that cNIC can increase silent synapses in MSNs, as observed with cocaine and opiates, and alter the regulation of corticostriatal plasticity. Prior work has characterized cocaine- and morphine-induced upregulation of silent synapses in the ventral striatum; we show it can occur in the dorsal striatum, a region associated with later stages of addiction, craving, and cue-induced relapse.

Loss of Plasticity in the D2-Accumbens Pallidal Pathway Promotes Cocaine Seeking.

Distinct populations of D1- and D2-dopamine receptor-expressing medium spiny neurons (D1-/D2-MSNs) comprise the nucleus accumbens, and activity in D1-MSNs promotes, whereas activity in D2-MSNs inhibits, motivated behaviors. We used chemogenetics to extend D1-/D2-MSN cell specific regulation to cue-reinstated cocaine seeking in a mouse model of self-administration and relapse, and found that either increasing activity in D1-MSNs or decreasing activity in D2-MSNs augmented cue-induced reinstatement. Both D1- and D2-MSNs provide substantial GABAergic innervation to the ventral pallidum, and chemogenetic inhibition of ventral pallidal neurons blocked the augmented reinstatement elicited by chemogenetic regulation of either D1- or D2-MSNs. Because D1- and D2-MSNs innervate overlapping populations of ventral pallidal neurons, we next used optogenetics to examine whether changes in synaptic plasticity in D1- versus D2-MSN GABAergic synapses in the ventral pallidum could explain the differential regulation of VP activity. In mice trained to self-administer cocaine, GABAergic LTD was abolished in D2-, but not in D1-MSN synapses. A µ opioid receptor antagonist restored GABA currents in D2-, but not D1-MSN synapses of cocaine-trained mice, indicating that increased enkephalin tone on presynaptic µ opioid receptors was responsible for occluding the LTD. These results identify a behavioral function for D1-MSN innervation of the ventral pallidum, and suggest that losing LTDGABA in D2-MSN, but not D1-MSN input to ventral pallidum may promote cue-induced reinstatement of cocaine-seeking. SIGNIFICANCE STATEMENT: More than 90% of ventral striatum is composed of two cell types, those expressing dopamine D1 or D2 receptors, which exert opposing roles on motivated behavior. Both cell types send GABAergic projections to the ventral pallidum and were found to differentially promote cue-induced reinstatement of cocaine seeking via the ventral pallidum. Furthermore, after cocaine self-administration, synaptic plasticity was selectively lost in D2, but not D1 inputs to the ventral pallidum. The selective impairment in D2 afferents may promote the influence of D1 inputs to drive relapse to cocaine seeking.

NMDAR dependent intracellular responses associated with cocaine conditioned place preference behavior.

The aim of this study was to investigate the intracellular responses associated with the acquisition and expression of cocaine-context associations. ERK (extracellular regulated kinase), CREB (cAMP responsive element binding protein), FosB and ΔFosB proteins were of particular interest due to their involvement in cocaine reward and in synaptic plasticity underlying learning and memory. We used the conditioned place preference (CPP) paradigm, which employs a Pavlovian conditioning procedure to establish an association between a drug-paired environment and the drug's rewarding effects, to study the role of these signaling pathways in cocaine-context associations. N-methyl-D-aspartate receptor (NMDAR) antagonism prior to cocaine administration during conditioning blocked the acquisition of cocaine CPP and reduced Nucleus Accumbens (NAc) phosphorylated-ERK (pERK) and phosphorylated CREB (pCREB) levels following the CPP test (drug-free). We also show that cocaine-induced increases in Caudate Putamen (CPu) FosB and ΔFosB levels are decreased after MK-801 pre-treatment during conditioning. In addition, our results provide evidence for the involvement of striatal SIRT (Silent Information Regulator of Transcription) proteins in cocaine-CPP. These results will aid in the advancement of general knowledge about the molecular formation and retrieval of cocaine-associated memories that can be used in the future when designing treatments for cocaine addiction that target both prevention and relapse.

Cannabinoid-induced depression of synaptic transmission is switched to stimulation when dopaminergic tone is increased in the globus pallidus of the rodent.

Because activation of D2 receptors reverses the neurochemical effects of cannabinoids, we examined whether increasing dopaminergic tone in the globus pallidus (GPe) switches cannabinoid induced depression of synaptic transmission. GABAergic synaptic currents evoked in pallidal neurons by stimulation of striatal projections (IPSCs) were depressed by perfusion with the CB1R agonist ACEA. Coactivation of D2Rs with quinpirole converted the depression into stimulation. Pretreatment with pertussis toxin (PTX) to limit Gi/o protein coupling also switched the CB1R-induced depression of IPSCs. The stimulation of IPSCs was blocked by the selective PKA blocker H89. Changes in the paired pulse ratio during both inhibitory and stimulatory responses indicate that the effects are due to changes in transmitter release. Postsynaptic depolarization induces endocannabinoid release that inhibits transmitter release (DSI). When D2Rs were activated with quinpirole, depolarization increased transmission instead of depressing it. This increase was blocked by AM251. We also examined the effects of CB1R/D2R coactivation on cAMP accumulation in the GPe to further verify that the AC/PKA cascade is involved. CB1R/D2R coactivation converted the inhibition of cAMP seen when each receptor is stimulated alone into a stimulation. We also determined the effects on turning behavior of unilateral injection of ACEA into the GPe of awake animals and its modification by dopamine antagonists. Blockade of D2 family receptors with sulpiride antagonized the motor effects of ACEA. We show, for the first time, that cannabinoid-inhibition of synaptic transmission in the GPe becomes a stimulation after D2Rs or PTX treatment and that the switch is probably relevant for the control of motor behavior.

Parkinson's disease-like forelimb akinesia induced by BmK I, a sodium channel modulator.

Parkinson's disease (PD) is a neurodegenerative disorder and characterized by motor disabilities which are mostly linked with high levels of synchronous oscillations in the basal ganglia neurons. Voltage-gated sodium channels (VGSCs) play a vital role in the abnormal electrical activity of neurons in the globus pallidus (GP) and the subthalamic nucleus (STN) in PD. BmK I, a α-like toxin purified from the Chinese scorpion Buthus martensi Karsch, has been identified a site-3-specific modulator of VGSCs. The present study shows that forelimb akinesia can be induced by the injection of BmK I into the globus pallidus (GP) in rats. In addition, BmK I cannot produce neuronal damage in vivo and in vitro at 24h after treatment, indicating that the forelimb akinesia does not result from neuronal damage. Electrophysiological studies further revealed that the inactivated Na(+) currents were showed to be more vulnerably modulated by BmK I than the activated Na(+) currents in human neuron-like SHSY5Y cells. Furthermore, the modulation of BmK I on inactivation was preferentially attributed to fast inactivation rather than slow inactivation. Therefore, the PD-like forelimb akinesia may result from the modulation of sodium channels in neuron by BmK I. These findings not only suggest that BmK I may be an effective and novel molecule for the study of pathogenesis in PD but also support the idea that VGSCs play a crucial role in the motor disabilities in PD.

Dopamine-dependent modulation of rat globus pallidus excitation by nicotine acetylcholine receptors.

The globus pallidus (GP) coordinates information processing in the basal ganglia nuclei. The contribution of nicotinic cholinergic receptors (nAChRs) to the spiking activity of GP neurons is largely unknown. Several studies have reported that the effect of nAChRs in other nuclei depends on dopaminergic input. Via in vivo single unit extracellular recordings and intranuclear drug infusions, we analyzed the effects of local activation and blockade of nAChRs in neurons of both sham and 6-hydroxydopamine (6-OHDA)-lesioned rats. In sham rats, the local application of nicotine and edrophonium (an acetylcholinesterase inhibitor) increases GP neurons spiking rate. Local application of mecamylamine, a neuronal nicotinic cholinergic antagonist, diminishes pallidal neurons spiking rate, an effect not produced by d-tubocurarine, a peripheral nicotinic cholinergic antagonist. Moreover, mecamylamine blocks the excitatory effect evoked by nicotine and edrophonium. In 6-OHDA-lesioned rats, local infusion of nicotine does not change pallidal neurons firing rate. Our results show that there is a tonic cholinergic input to the GP that increases their spiking rate through the activation of nAChRs and that this effect depends on functional dopaminergic pathways.

The Effect of General Anesthesia on the Microelectrode Recordings From Pallidal Neurons in Patients With Dystonia.

BACKGROUND: The most common anesthetic technique for patients undergoing insertion of deep brain stimulators (DBS) is local anesthesia with or without conscious sedation as this facilitates intraoperative microelectrode recordings (MERs) for target localization. However, general anesthesia (GA) may be needed in some of the patients especially those with dystonia. The purpose of our study was to determine the effects of GA on MERs from pallidal neurons in patients with dystonia undergoing DBS implantation surgery. METHODS: After IRB approval, we retrospectively reviewed the medical records of all patients who had insertion of DBS from January 2009 to December 2013. Data collected and analyzed included demographics, indications for DBS, targets of insertion, MER, and anesthetic management. From the records we identified patients with dystonia who received GA for DBS insertion. We then compared the MER data under GA with the data from patients who had surgery under local anesthesia only during the same time period. Because of the small sample size, the effects of various anesthetic regiments on MER and localization of target nuclei were compared qualitatively. RESULTS: Of the 435 patients who underwent DBS insertion during the study period, 20 (4.3%) patients had GA for the procedure. Dystonia was the most common indication for GA (16/20 patients, 80%). Good-quality MER data obtained from 10 patients with dystonia under GA was compared with 8 patients who had no sedation for the procedure. Administration of GA made target localization difficult due to suppression of both spontaneous and evoked neuronal discharges from internal globus pallidus. Although not studied systematically, propofol (>100 mcg/kg/min) seemed to suppress pallidal discharges more than GA with a lower dose of propofol (<75 mcg/kg/min), remifentanil, and 0.2% to 0.4% end-tidal sevoflurane or desflurane. CONCLUSIONS: Our retrospective review suggests that there was a difference in spontaneous and evoked neuronal discharges with MER performed under GA compared with no sedation. MER recordings during GA appeared most robust during a combination of anesthetics including low-dose propofol infusion, remifentanil, and a low concentration of either sevoflurane or desflurane. Our findings can inform a power analysis to determine the sample size that would be required to prospectively test the hypothesis that there is a difference in spontaneous and evoked neuronal discharges with MER performed under GA compared with no sedation.

Histamine H3 receptor activation counteracts adenosine A2A receptor-mediated enhancement of depolarization-evoked [3H]-GABA release from rat globus pallidus synaptosomes.

High levels of histamine H3 receptors (H3Rs) are found in the globus pallidus (GP), a neuronal nucleus in the basal ganglia involved in the control of motor behavior. By using rat GP isolated nerve terminals (synaptosomes), we studied whether H3R activation modified the previously reported enhancing action of adenosine A2A receptor (A2AR) stimulation on depolarization-evoked [(3)H]-GABA release. At 3 and 10 nM, the A2AR agonist CGS-21680 enhanced [(3)H]-GABA release induced by high K(+) (20 mM) and the effect of 3 nM CGS-21680 was prevented by the A2AR antagonist ZM-241385 (100 nM). The presence of presynaptic H3Rs was confirmed by the specific binding of N-α-[methyl-(3)H]-histamine to membranes from GP synaptosomes (maximum binding, Bmax, 1327 ± 79 fmol/mg protein; dissociation constant, Kd, 0.74 nM), which was inhibited by the H3R ligands immepip, clobenpropit, and A-331440 (inhibition constants, Ki, 0.28, 8.53, and 316 nM, respectively). Perfusion of synaptosomes with the H3R agonist immepip (100 nM) had no effect on K(+)-evoked [(3)H]-GABA release, but inhibited the stimulatory action of A2AR activation. In turn, the effect of immepip was blocked by the H3R antagonist clobenpropit, which had no significant effect of its own on K(+)-induced [(3)H]-GABA release. These data indicate that H3R activation selectively counteracts the facilitatory action of A2AR stimulation on GABA release from striato-pallidal projections.

High-frequency electrical stimulation of the subthalamic nucleus excites target structures in a model using c-fos immunohistochemistry.

Deep-brain stimulation at high frequencies (HFS) directed to the subthalamic nucleus (STN) is used increasingly to treat patients with Parkinson's disease. However, the mechanism of action by which HFS of the STN achieves its therapeutic effects remains unresolved. Insofar as lesions of the STN have similar therapeutic benefit, a favored hypothesis is that HFS acts by suppressing neural activity in the STN. The purpose of the present study was to exploit prior observations that exposure to ether anesthesia in a rodent model evokes c-fos expression (a marker of neural activation) in the STN and its efferent structures, the globus pallidus, entopeduncular nucleus and substantia nigra. We showed first that exposure to ether induced a profound oscillatory pattern of neural activity in the STN and SNr, which could explain the marked induction of c-fos immunoreactivity in these structures. Secondly, inhibition of the STN by local injections of the GABA agonist, muscimol, suppressed ether-evoked c-fos expression in all target structures. This showed that excitation of target structures in the ether model originated, at least in part, from the STN. Thirdly, and contrary to expectation, HFS of the STN increased further the expression of c-fos in the STN target structures of animals treated with ether. Finally, we demonstrated, in the absence of ether treatment, that HFS and chemical stimulation of the STN with local injections of kainic acid both induced c-fos expression in the globus pallidus, entopeduncular nucleus and substantia nigra. Together these results suggest that the principal action of STN stimulation at high frequencies is to excite rather than inhibit its efferent targets. Given that Parkinsonism has been associated with increased levels of inhibitory output activity from the basal ganglia, it is unlikely that excitation of output structures revealed in this study provides a basis for deep-brain stimulation's therapeutic action.

Optogenetic evidence that pallidal projections, not nigral projections, from the nucleus accumbens core are necessary for reinstating cocaine seeking.

The core subcompartment of the nucleus accumbens (NAcore) contributes significantly to behavioral responses following motivationally relevant stimuli, including drug-induced, stress-induced, and cue-induced reinstatement of cocaine seeking. Projections from NAcore that could carry information necessary to initiate reinstated cocaine seeking include outputs via the indirect pathway to the dorsolateral subcompartment of the ventral pallidum (dlVP) and through the direct pathway to the medial substantia nigra (SN). Here we used an optogenetic strategy to determine whether the dlVP or nigral projections from the NAcore are necessary for cocaine seeking initiated by a cocaine and conditioned cue combination in rats extinguished from cocaine self-administration. Rats were pretreated in the NAcore with an adeno-associated virus expressing the inhibitory opsin archaerhodopsin, and fiber-optic cannulae were implanted above the indirect pathway axon terminal field in the dlVP, or the direct pathway terminal field in the SN. Inhibiting the indirect pathway to the dlVP, but not the direct pathway to the SN, prevented cocaine-plus-cue-induced reinstatement. We also examined projections back to the NAcore from the ventral tegmental area (VTA) and dlVP. Inhibiting the dlVP to NAcore projection did not alter, while inhibiting VTA afferents abolished reinstated cocaine seeking. Localization of green fluorescent protein reporter expression and whole-cell patch electrophysiology were used to verify opsin expression. These data reveal a circuit involving activation of VTA inputs to the NAcore and NAcore projections through the indirect pathway to the dlVP as critical for cocaine-plus-cue-induced reinstatement of cocaine seeking.

The ventral striato-pallidal pathway mediates the effect of predictive learning on choice between goal-directed actions.

The nucleus accumbens shell (NAc-S) plays an important role in the way stimuli that predict reward affect the performance of, and choice between, goal-directed actions in tests of outcome-specific Pavlovian-instrumental transfer (PIT). The neural processes involved in PIT downstream of the ventral striatum are, however, unknown. The NAc-S projects prominently to the ventral pallidum (VP), and in the current experiments, we assessed the involvement of the NAc-S to VP projection in specific PIT in rats. We first compared expression of the immediate-early gene c-Fos in the medial (VP-m) and lateral (VP-l) regions of the VP and in addition, used the retrograde tracer Fluoro-gold combined with c-Fos to assess the involvement of these pathways during PIT. Although there was no evidence of differential activation in neurons in the VP-l, the VP-m showed a selective increase in activity in rats tested for PIT compared with appropriate controls, as did NAc-S neurons projecting to the VP-m. To confirm that VP-m activity is important for PIT, we inactivated this region before test and found this inactivation blocked the influence of predictive learning on choice. Finally, to confirm the functional importance of the NAc-S to VP-m pathway we used a disconnection procedure, using asymmetrical inactivation of the NAc-S and either the ipsilateral or contralateral VP-m. Specific PIT was blocked but only by inactivation of the NAc-S and VP-m in contralateral hemispheres. These results suggest that the NAc-S and VP-m form part of a circuit mediating the effects of predictive learning on choice.