Modulation of the Blood-Brain Barrier by Sigma-1R Activation

Sigma non-opioid intracellular receptor 1 (Sigma-1R) is an intracellular chaperone protein residing on the endoplasmic reticulum at the mitochondrial-associated membrane (MAM) region. Sigma-1R is abundant in the brain and is involved in several physiological processes as well as in various disease states. The role of Sigma-1R at the blood-brain barrier (BBB) is incompletely characterized. In this study, the effect of Sigma-1R activation was investigated in vitro on rat brain microvascular endothelial cells (RBMVEC), an important component of the blood-brain barrier (BBB), and in vivo on BBB permeability in rats. The Sigma-1R agonist PRE-084 produced a dose-dependent increase in mitochondrial calcium, and mitochondrial and cytosolic reactive oxygen species (ROS) in RBMVEC. PRE-084 decreased the electrical resistance of the RBMVEC monolayer, measured with the electric cell-substrate impedance sensing (ECIS) method, indicating barrier disruption. These effects were reduced by pretreatment with Sigma-1R antagonists, BD 1047 and NE 100. In vivo assessment of BBB permeability in rats indicates that PRE-084 produced a dose-dependent increase in brain extravasation of Evans Blue and sodium fluorescein brain; the effect was reduced by the Sigma-1R antagonists. Immunocytochemistry studies indicate that PRE-084 produced a disruption of tight and adherens junctions and actin cytoskeleton. The brain microcirculation was directly visualized in vivo in the prefrontal cortex of awake rats with a miniature integrated fluorescence microscope (aka, miniscope; Doric Lenses Inc.). Miniscope studies indicate that PRE-084 increased sodium fluorescein extravasation in vivo. Taken together, these results indicate that Sigma-1R activation promoted oxidative stress and increased BBB permeability.

Intra-Tumoral Nerve-Tracing in a Novel Syngeneic Model of High-Grade Serous Ovarian Carcinoma

Dense tumor innervation is associated with enhanced cancer progression and poor prognosis. We observed innervation in breast, prostate, pancreatic, lung, liver, ovarian, and colon cancers. Defining innervation in high-grade serous ovarian carcinoma (HGSOC) was a focus since sensory innervation was observed whereas the normal tissue contains predominantly sympathetic input. The origin, specific nerve type, and the mechanisms promoting innervation and driving nerve-cancer cell communications in ovarian cancer remain largely unknown. The technique of neuro-tracing enhances the study of tumor innervation by offering a means for identification and mapping of nerve sources that may directly and indirectly affect the tumor microenvironment. Here, we establish a murine model of HGSOC and utilize image-guided microinjections of retrograde neuro-tracer to label tumor-infiltrating peripheral neurons, mapping their source and circuitry. We show that regional sensory neurons innervate HGSOC tumors. Interestingly, the axons within the tumor trace back to local dorsal root ganglia as well as jugular-nodose ganglia. Further manipulations of these tumor projecting neurons may define the neuronal contributions in tumor growth, invasion, metastasis, and responses to therapeutics.

Choline-Sigma-1R as an Additional Mechanism for Potentiation of Orexin by Cocaine

Orexin A, an endogenous peptide involved in several functions including reward, acts via activation of orexin receptors OX1 and OX2, Gq-coupled GPCRs. We examined the effect of a selective OX1 agonist, OXA (17-33) on cytosolic calcium concentration, [Ca2+]i, in neurons of nucleus accumbens, an important area in the reward circuit. OXA (17-33) increased [Ca2+]i in a dose-dependent manner; the effect was prevented by SB-334867, a selective OX1 receptors antagonist. In Ca2+-free saline, the OXA (17-33)-induced increase in [Ca2+]i was not affected by pretreatment with bafilomycin A1, an endo-lysosomal calcium disrupter, but was blocked by 2-APB and xestospongin C, antagonists of inositol-1,4,5-trisphosphate (IP3) receptors. Pretreatment with VU0155056, PLD inhibitor, or BD-1047 and NE-100, Sigma-1R antagonists, reduced the [Ca2+]i response elicited by OXA (17-33). Cocaine potentiated the increase in [Ca2+]i by OXA (17-33); the potentiation was abolished by Sigma-1R antagonists. Our results support an additional signaling mechanism for orexin A-OX1 via choline-Sigma-1R and a critical role for Sigma-1R in the cocaine-orexin A interaction in nucleus accumbens neurons.

Assessment of Blood-Brain Barrier Permeability Using Miniaturized Fluorescence Microscopy in Freely Moving Rats

We report here the method of visualization of brain microcirculation and assessment of blood-brain barrier (BBB) permeability changes using the miniature integrated fluorescence microscope (i.e., miniscope) technology in awake, freely moving rats. The imaging cannula is implanted in the brain area of interest of anesthetized adult rats. After recovery and habituation, sodium fluorescein, a low-molecular-weight tracer, is injected i.v. Fluorescence intensity in the vicinity of microvessels, as an indicator of BBB permeability, is then recorded in vivo via the miniscope for extended periods of time. The method can be used to assess the changes in BBB permeability produced by pharmacologic agents; in this case, the drug of interest is administered after sodium fluorescein. An increase in the sodium fluorescein extravasation in brain microcirculation demonstrates an increase in BBB permeability. The method described here allows a high-resolution visualization of real-time changes in BBB permeability in awake, freely moving rats.

Direct evidence of bradycardic effect of omega-3 fatty acids acting on nucleus ambiguus

Docosahexaenoic acid (DHA) an omega-3 polyunsaturated fatty acid, is an agonist of FFA1 receptor. DHA administration reduces the heart rate via unclear mechanisms. We examined the effect of DHA on neurons of nucleus ambiguus that provide the parasympathetic control of heart rate. DHA produced a dose-dependent increase in cytosolic Ca²⁺ concentration in cardiac-projecting nucleus ambiguus neurons; the effect was prevented by GW1100, a FFA1 receptor antagonist. DHA depolarized cultured nucleus ambiguus neurons via FFA1 activation. Bilateral microinjection of DHA into nucleus ambiguus produced bradycardia in conscious rats. Our results indicate that DHA decreases heart rate by activation of FFA1 receptor on cardiac-projecting nucleus ambiguus neurons.

Sex differences in the effect of the FKBP5 inhibitor SAFit2 on anxiety and stress-induced reinstatement following cocaine self-administration

Cocaine use and withdrawal prompt stress system responses. Stress and the negative affective state produced by cocaine withdrawal are major triggers for relapse. FKBP5 is a co-chaperone of the glucocorticoid receptor and regulates HPA axis negative feedback. The role of FKBP5 in cocaine-related behaviors has not been studied. The FKBP5 inhibitor SAFit2 was used to examine the role of FKBP5 in anxiety-like behavior during early cocaine withdrawal and in stress-induced reinstatement following cocaine self-administration in male and female rats. Withdrawal from cocaine self-administration resulted in heightened anxiety-like behavior in female rats, which was significantly attenuated by SAFit2 administration. SAFit2 pretreatment prior to stress-induced reinstatement to cocaine seeking significantly reduced active lever presses of males. In female rats, SAFit2 administration prevented stress-induced reinstatement for rats in metestrus or diestrus, but not proestrus or estrus phases at the time of reinstatement. These data suggest an important role for FKBP5 in stress-related behaviors following cocaine self-administration, particularly in females.

Glycogen synthase kinase-3 signaling in cellular and behavioral responses to psychostimulant drugs

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase implicated in numerous physiological processes and cellular functions through its ability to regulate the function of many proteins, including transcription factors and structural proteins. GSK-3β has been demonstrated to function as a regulator of multiple behavioral processes induced by drugs of abuse, particularly psychostimulant drugs. In this review, we provide an overview of the regulation of GSK-3β activity produced by psychostimulants, and the role of GSK-3β signaling in psychostimulant-induced behaviors including drug reward, associative learning and memory which play a role in the maintenance of drug-seeking. Evidence supports the conclusion that GSK-3β is an important component of the actions of psychostimulant drugs and that GSK-3β is a valid target for developing novel therapeutics. Additional studies are required to examine the role of GSK-3β in distinct cell types within the mesolimbic and memory circuits to further elucidate the mechanisms related to the acquisition, consolidation, and recall of drug-related memories, and potentially countering neuroadaptations that reinforce drug-seeking behaviors that maintain drug dependence.

Acute cocaine administration alters permeability of blood-brain barrier in freely-moving rats- Evidence using miniaturized fluorescence microscopy

BACKGROUND

Cocaine has a variety of negative effects on the central nervous system, including reports of decreased barrier function of brain microvascular endothelial cells. However, few studies have directly shown the effects of cocaine on blood-brain barrier (BBB) function in vivo. The miniature integrated fluorescence microscope (i.e., miniscope) technology was used to visualize cocaine-induced changes in BBB permeability in awake, freely-moving rats.

METHODS

The miniscope was implanted in the prefrontal cortex of adult male rats. After recovery and acclimation, rats received an injection of cocaine (5-20 mg/kg ip) 15 minutes following iv infusion of sodium fluorescein, a low molecular weight tracer. Fluorescence intensity was recordedin vivo via the miniscope for 30 minutes or 24 hours post cocaine administration and served as an indicator of BBB permeability.

RESULTS

Results demonstrate that cocaine increased the sodium fluorescein extravasation in brain microcirculation in a dose-dependent manner 30 minutes, but not 24 hours after administration.

CONCLUSION

We report for the first time using direct visualization of brain microcirculation with the miniscope technology in awake, freely-moving rats, that acute cocaine administration produced a transient increase in the BBB permeability.

Glycogen Synthase Kinase 3β in the Ventral Hippocampus is Important for Cocaine Reward and Object Location Memory

The ventral hippocampus is a component of the neural circuitry involved with context-associated memory for reward and generation of appropriate behavioral responses to context. Glycogen synthase kinase 3 beta (GSK3β) has been linked to the maintenance of synaptic plasticity, contextual memory retrieval, and is involved in the reconsolidation of cocaine-associated contextual memory. In this study, the effects of targeted downregulation of GSK3β in the ventral hippocampus were examined on a series of behavioral tests for assessing drug reward-context association and non-reward related memory. The Cre/loxP site-specific recombination system was used to knockdown GSK3β through bilateral stereotaxic delivery of an adeno-associated virus expressing Cre-recombinase (AAV-Cre) into the ventral hippocampus of adult mice homozygous for a floxed GSK3β allele. GSK3β floxed mice injected with AAV-Cre had a loss of 56-75% of GSK3β in the ventral hippocampus and displayed diminished development of cocaine conditioned place preference, but not morphine place preference as compared with wild-type mice injected with AAV-Cre or GSK3β floxed mice injected with a control virus, AAV-GFP. Impaired object location memory was observed in mice with GSK3β downregulation in the ventral hippocampus, but novel object recognition remained intact. These results indicate that GSK3β signaling in the ventral hippocampus is differentially involved in the formation of place-drug reward association dependent upon drug class. Additionally, ventral hippocampal GSK3β signaling is important in detection of discrete spatial cues, but not recognition memory for objects.

Activation of GSK3β induced by recall of cocaine reward memories is dependent on GluN2A/B NMDA receptor signaling

Glycogen synthase kinase-3β (GSK3β) is a critical regulator of the balance between long-term depression and long-term potentiation which is essential for learning and memory. Our previous study demonstrated that GSK3β activity is highly induced during cocaine memory reactivation, and that reconsolidation of cocaine reward memory is attenuated by inhibition of GSK3β. NMDA receptors and protein phosphatase 1 (PP1) are activators of GSK3β. Thus, this study investigated the roles of NMDA receptor subtypes and PP1in the reconsolidation of cocaine contextual reward memory. Cocaine contextual memories were established and evaluated using cocaine conditioned place preference methods. The regulation of GSK3β activity in specific brain areas was assessed by measuring its phosphorylation state using immunoblot assays. Mice underwent cocaine place conditioning for 8 days and were tested for place preference on day 9. Twenty-four hours later, mice were briefly confined to the compartment previous paired with cocaine to reactivate cocaine-associated memories. Administration of the GluN2A- and GluN2B-NMDA receptor antagonists, NVP-AAM077 and ifenprodil, respectively, immediately following recall abrogated an established cocaine place preference, while preventing the activation of GSK3β in the amygdala, nucleus accumbens, and hippocampus during cocaine memory reactivation. PP1 inhibition with okadaic acid also blocked the activation of GSK3β and attenuated a previously established cocaine place preference. These findings suggest that the dephosphorylation of GSK3β that occurred upon activation of cocaine-associated reward memories may be initiated by the activation of PP1 during the induction of NMDA receptor-dependent reconsolidation of cocaine mnemonic traces. Moreover, the importance of NMDA receptors and PP1 in reconsolidation of cocaine memory makes them potential therapeutic targets in treatment of cocaine use disorder and prevention of relapse.

Differential Roles of Accumbal GSK3β in Cocaine versus Morphine-Induced Place Preference, U50,488H-Induced Place Aversion, and Object Memory

Previous research has demonstrated that activity of glycogen synthase kinase-3 (GSK3) is necessary for the rewarding effects of cocaine. In the present study, a conditional GSK3β gene knockdown model was used to determine if GSK3β activity specifically in the nucleus accumbens is important for cocaine conditioned reward. The roles of accumbal GSK3β in morphine conditioned reward, trans-(±)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide methanesulfonate salt (U50,488H)-induced conditioned place aversion, and cognitive function were also studied. Adult male and female GSK3β-floxed or wild-type mice were injected with adeno-associated virus/Cre into the nucleus accumbens to reduce expression of GSK3β and underwent behavioral testing 4 weeks later. The development of cocaine-induced conditioned place preference was significantly attenuated in mice with reduced levels of GSK3β in the nucleus accumbens, whereas the development of morphine-induced place preference remained intact. Conditional knockdown of GSK3β in the accumbens prevented the development of conditioned aversion produced by U50,488H, a κ-opioid receptor agonist. Cognitive memory tests revealed deficits in object location memory, but not novel object recognition in mice with accumbal GSK3β knockdown. These data demonstrate that GSK3β in the nucleus accumbens is required for cocaine conditioned place preference and U50,488H conditioned place aversion, as well as spatial memory in object location task, indicating differential roles of GSK3β in the psychostimulant and opiate reward process, as well as in memory for spatial locations and object identity. SIGNIFICANCE STATEMENT: Knockdown of GSK3β in the nucleus accumbens attenuated the development of cocaine-induced place preference, as well as conditioned place aversion to U50,488H, a κ-opioid receptor agonist. In contrast, the development of morphine place preference was not altered by GSK3β knockdown. GSK3β knockdown in nucleus accumbens impaired performance in the object location task, but not the novel object recognition task. These results elucidate different physiological roles of accumbal GSKβ in conditioned reward, aversion, and memory.

Choline Is an Intracellular Messenger Linking Extracellular Stimuli to IP3-Evoked Ca2+ Signals through Sigma-1 Receptors

Sigma-1 receptors (Sig-1Rs) are integral ER membrane proteins. They bind diverse ligands, including psychoactive drugs, and regulate many signaling proteins, including the inositol 1,4,5-trisphosphate receptors (IP3Rs) that release Ca2+ from the ER. The endogenous ligands of Sig-1Rs are unknown. Phospholipase D (PLD) cleaves phosphatidylcholine to choline and phosphatidic acid (PA), with PA assumed to mediate all downstream signaling. We show that choline is also an intracellular messenger. Choline binds to Sig-1Rs, it mimics other Sig-1R agonists by potentiating Ca2+ signals evoked by IP3Rs, and it is deactivated by metabolism. Receptors, by stimulating PLC and PLD, deliver two signals to IP3Rs: IP3 activates IP3Rs, and choline potentiates their activity through Sig-1Rs. Choline is also produced at synapses by degradation of acetylcholine. Choline uptake by transporters activates Sig-1Rs and potentiates Ca2+ signals. We conclude that choline is an endogenous agonist of Sig-1Rs linking extracellular stimuli, and perhaps synaptic activity, to Ca2+ signals.

Modulation of cardiac vagal tone by bradykinin acting on nucleus ambiguus

Bradykinin (BK), a component of the kallikrein-kininogen-kinin system exerts multiple effects via B1 and B2 receptor activation. In the cardiovascular system, bradykinin has cardioprotective and vasodilator properties. We investigated the effect of BK on cardiac-projecting neurons of nucleus ambiguus, a key site for the parasympathetic cardiac regulation. BK produced a dose-dependent increase in cytosolic Ca²⁺ concentration. Pretreatment with HOE140, a B2 receptor antagonist, but not with R715, a B1 receptor antagonist, abolished the response to BK. A selective B2 receptor agonist, but not a B1 receptor agonist, elicited an increase in cytosolic Ca²⁺ similarly to BK. Inhibition of N-type voltage-gated Ca²⁺ channels with ω-conotoxin GVIA had no effect on the Ca²⁺ signal produced by BK, while pretreatment with ω-conotoxin MVIIC, a blocker of P/Q-type of Ca²⁺ channels, significantly diminished the effect of BK. Pretreatment with xestospongin C and 2-aminoethoxydiphenyl borate, antagonists of inositol 1,4,5-trisphosphate receptors, abolished the response to BK. Inhibition of ryanodine receptors reduced the BK-induced Ca²⁺ increase, while disruption of lysosomal Ca²⁺ stores with bafilomycin A1 did not affect the response. BK produced a dose-dependent depolarization of nucleus ambiguus neurons, which was prevented by the B2 receptor antagonist. In vivo studies indicate that microinjection of BK into nucleus ambiguus elicited bradycardia in conscious rats via B2 receptors. In summary, in cardiac vagal neurons of nucleus ambiguus, BK activates B2 receptors promoting Ca²⁺ influx and Ca²⁺ release from endoplasmic reticulum, and membrane depolarization; these effects are translated in vivo by bradycardia.

High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak

Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

Ceftriaxone attenuates acute cocaine-evoked dopaminergic neurotransmission in the nucleus accumbens of the rat

BACKGROUND AND PURPOSE

Ceftriaxone is a β-lactam antibiotic and glutamate transporter activator that reduces the reinforcing effects of psychostimulants. Ceftriaxone also reduces locomotor activation following acute psychostimulant exposure, suggesting that alterations in dopamine transmission in the nucleus accumbens contribute to its mechanism of action. In the present studies we tested the hypothesis that pretreatment with ceftriaxone disrupts acute cocaine-evoked dopaminergic neurotransmission in the nucleus accumbens.

EXPERIMENTAL APPROACH

Adult male Sprague-Dawley rats were pretreated with saline or ceftriaxone (200 mg kg(-1) , i.p. × 10 days) and then challenged with cocaine (15 mg kg(-1) , i.p.). Motor activity, dopamine efflux (via in vivo microdialysis) and protein levels of tyrosine hydroxylase (TH), the dopamine transporter and organic cation transporter as well as α-synuclein, Akt and GSK3β were analysed in the nucleus accumbens.

KEY RESULTS

Ceftriaxone-pretreated rats challenged with cocaine displayed reduced locomotor activity and accumbal dopamine efflux compared with saline-pretreated controls challenged with cocaine. The reduction in cocaine-evoked dopamine levels was not counteracted by excitatory amino acid transporter 2 blockade in the nucleus accumbens. Pretreatment with ceftriaxone increased Akt/GSK3β signalling in the nucleus accumbens and reduced levels of dopamine transporter, TH and phosphorylated α-synuclein, indicating that ceftriaxone affects numerous proteins involved in dopaminergic transmission.

CONCLUSIONS AND IMPLICATIONS

These results are the first evidence that ceftriaxone affects cocaine-evoked dopaminergic transmission, in addition to its well-described effects on glutamate, and suggest that its ability to attenuate cocaine-induced behaviours, such as psychomotor activity, is due in part to reduced dopaminergic neurotransmission in the nucleus accumbens.

Mechanisms of activation of nucleus accumbens neurons by cocaine via sigma-1 receptor-inositol 1,4,5-trisphosphate-transient receptor potential canonical channel pathways

Cocaine promotes addictive behavior primarily by blocking the dopamine transporter, thus increasing dopamine transmission in the nucleus accumbens (nAcc); however, additional mechanisms are continually emerging. Sigma-1 receptors (σ1Rs) are known targets for cocaine, yet the mechanisms underlying σ1R-mediated effects of cocaine are incompletely understood. The present study examined direct effects of cocaine on dissociated nAcc neurons expressing phosphatidylinositol-linked D1 receptors. Endoplasmic reticulum-located σ1Rs and inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) were targeted using intracellular microinjection. IP3 microinjection robustly elevated intracellular Ca(2+) concentration, [Ca(2+)]i. While cocaine alone was devoid of an effect, the IP3-induced response was σ1R-dependently enhanced by cocaine co-injection. Likewise, cocaine augmented the [Ca(2+)]i increase elicited by extracellularly applying an IP3-generating molecule (ATP), via σ1Rs. The cocaine-induced enhancement of the IP3/ATP-mediated Ca(2+) elevation occurred at pharmacologically relevant concentrations and was mediated by transient receptor potential canonical channels (TRPC). IP3 microinjection elicited a slight, transient depolarization, further converted to a greatly enhanced, prolonged response, by cocaine co-injection. The cocaine-triggered augmentation was σ1R-dependent, TRPC-mediated and contingent on [Ca(2+)]i elevation. ATP-induced depolarization was similarly enhanced by cocaine. Thus, we identify a novel mechanism by which cocaine promotes activation of D1-expressing nAcc neurons: enhancement of IP3R-mediated responses via σ1R activation at the endoplasmic reticulum, resulting in augmented Ca(2+) release and amplified depolarization due to subsequent stimulation of TRPC. In vivo, intra-accumbal blockade of σ1R or TRPC significantly diminished cocaine-induced hyperlocomotion and locomotor sensitization, endorsing a physio-pathological significance of the pathway identified in vitro.

Activity-regulated gene expression in immature neurons in the dentate gyrus following re-exposure to a cocaine-paired environment

Intense craving for drug and relapse are observed in addicts who are exposed to environmental stimuli associated with drug-taking behavior even after long periods of abstinence. The hippocampus is a brain region known to be involved in contextual processing, taking place predominantly in the septal hippocampus, and emotional processing, taking place predominantly in the temporal hippocampus. Conditioned place preference is an animal model of context-conditioned reward. The dentate gyrus is a hippocampal sub-region particularly important for the acquisition of cocaine-induced place preference and is a site of continuous neurogenesis, which has been implicated in the vulnerability to drug-taking behavior. Therefore, these experiments explored the role of newly generated neurons in drug reward-context association by examining the activation, as determined by expression of the immediate early gene cfos, of young and mature granule cells in the septal and temporal dentate gyrus of adult rats that were re-exposed to a drug-paired environment following the development of cocaine place preference. The overall level of cfos expression was increased in both the septal and temporal dentate gyrus of animals that developed place preference and were re-exposed to the drug paired environment compared with re-exposure to a neutral environment. Overall level of neurogenesis, as detected by the S-phase marker 5'-bromo-2'-deoxyuridine (BrdU) and the immature neuron marker doublecortin (DCX), was unaltered by cocaine conditioning. However, the number of activated new neurons (DCX + cfos) was greater in the temporal dentate gyrus of cocaine-conditioned rats re-exposed to the drug-paired environment as compared to those re-exposed to a neutral environment. Further understanding of the role of dentate gyrus neurogenesis on the conditioned effects of drugs of abuse may provide new insights into the role of this process in the expression of addictive behaviors.

Repeated cocaine enhances ventral hippocampal-stimulated dopamine efflux in the nucleus accumbens and alters ventral hippocampal NMDA receptor subunit expression

Dopaminergic neurotransmission in the nucleus accumbens is important for various reward-related cognitive processes including reinforcement learning. Repeated cocaine enhances hippocampal synaptic plasticity, and phasic elevations of accumbal dopamine evoked by unconditioned stimuli are dependent on impulse flow from the ventral hippocampus. Therefore, sensitized hippocampal activity may be one mechanism by which drugs of abuse enhance limbic dopaminergic activity. In this study, in vivo microdialysis in freely moving adult male Sprague-Dawley rats was used to investigate the effect of repeated cocaine on ventral hippocampus-mediated dopaminergic transmission within the medial shell of the nucleus accumbens. Following seven daily injections of saline or cocaine (20 mg/kg, ip), unilateral infusion of N-methyl-d-aspartate (NMDA, 0.5 μg) into the ventral hippocampus transiently increased both motoric activity and ipsilateral dopamine efflux in the medial shell of the nucleus accumbens, and this effect was greater in rats that received repeated cocaine compared to controls that received repeated saline. In addition, repeated cocaine altered NMDA receptor subunit expression in the ventral hippocampus, reducing the NR2A : NR2B subunit ratio. Together, these results suggest that repeated exposure to cocaine produces maladaptive ventral hippocampal-nucleus accumbens communication, in part through changes in glutamate receptor composition. A behaviorally sensitizing regimen of cocaine (20 mg/kg, ip 7 days) also sensitized ventral hippocampus (hipp)-mediated dopaminergic transmission within the nucleus accumbens (Nac) to NMDA stimulation (bolts). This was associated with reduced ventral hippocampal NR2A:NR2B subunit ratio, suggesting that repeated exposure to cocaine produces changes in hippocampal NMDA receptor composition that lead to enhanced ventral hippocampus-nucleus accumbens communication.

Decreased prefrontal cortex dopamine activity following adolescent social defeat in male rats: role of dopamine D2 receptors

RATIONALE

Adverse social experience in adolescence causes reduced medial prefrontal cortex (mPFC) dopamine (DA) and associated behavioral deficits in early adulthood.

OBJECTIVE

This study aims to determine whether mPFC DA hypofunction following social stress is specific to adolescent experience and if this results from stress-induced DA D2 receptor activation.

MATERIALS AND METHODS

Male rats exposed to repeated social defeat during adolescence or adulthood had mPFC DA activity sampled 17 days later. Separate experiments used freely moving microdialysis to measure mPFC DA release in response to adolescent defeat exposure. At P40, 49 and 56 mPFC DA turnover was assessed to identify when DA activity decreased in relation to the adolescent defeat experience. Finally, nondefeated adolescent rats received repeated intra-mPFC infusions of the D2 receptor agonist quinpirole, while another adolescent group received intra-mPFC infusions of the D2 antagonist amisulpride before defeat exposure.

RESULTS

Long-term decreases or increases in mPFC DA turnover were observed following adolescent or adult defeat, respectively. Adolescent defeat exposure elicits sustained increases in mPFC DA release, and DA turnover remains elevated beyond the stress experience before declining to levels below normal at P56. Activation of mPFC D2 receptors in nondefeated adolescents decreases DA activity in a similar manner to that caused by adolescent defeat, while defeat-induced reductions in mPFC DA activity are prevented by D2 receptor blockade.

CONCLUSIONS

Both the developing and mature PFC DA systems are vulnerable to social stress, but only adolescent defeat causes DA hypofunction. This appears to result in part from stress-induced activation of mPFC D2 autoreceptors.

Influence of chronic amphetamine treatment and acute withdrawal on serotonin synthesis and clearance mechanisms in the rat ventral hippocampus

Amphetamine withdrawal in both humans and rats is associated with increased anxiety states, which are thought to contribute to drug relapse. Serotonin in the ventral hippocampus mediates affective behaviors, and reduced serotonin levels in this region are observed in rat models of high anxiety, including during withdrawal from chronic amphetamine. This goal of this study was to understand the mechanisms by which reduced ventral hippocampus serotonergic neurotransmission occurs during amphetamine withdrawal. Serotonin synthesis (assessed by accumulation of serotonin precursor as a measure of the capacity of in vivo tryptophan hydroxylase activity), expression of serotonergic transporters, and in vivo serotonergic clearance using in vivo microdialysis were assessed in the ventral hippocampus in adult male Sprague Dawley rats at 24 h withdrawal from chronic amphetamine. Overall, results showed that diminished extracellular serotonin at 24 h withdrawal from chronic amphetamine was not accompanied by a change in capacity for serotonin synthesis (in vivo tryptophan hydroxylase activity), or serotonin transporter expression or function in the ventral hippocampus, but instead was associated with increased expression and function of organic cation transporters (low-affinity, high-capacity serotonin transporters). These findings suggest that 24 h withdrawal from chronic amphetamine reduces the availability of extracellular serotonin in the ventral hippocampus by increasing organic cation transporter-mediated serotonin clearance, which may represent a future pharmacological target for reversing anxiety states during drug withdrawal.

Withdrawal from chronic amphetamine produces persistent anxiety-like behavior but temporally-limited reductions in monoamines and neurogenesis in the adult rat dentate gyrus

Acute amphetamine administration activates monoaminergic pathways and increases systemic corticosterone, both of which influence anxiety states and adult dentate gyrus neurogenesis. Chronic amphetamine increases anxiety states in rats when measured at 24 h and at 2 weeks of withdrawal. However, the effects of chronic amphetamine exposure and withdrawal on long term anxiety-like behavior and adult neurogenesis in the dentate gyrus are unknown. Adult male rats were administered amphetamine (2.5 mg/kg, ip.) daily for two weeks. Anxiety-like behaviors were increased markedly in amphetamine-treated rats following four weeks of withdrawal from amphetamine. Plasma corticosterone level was unaltered by amphetamine treatment or withdrawal. However, norepinephrine and serotonin concentrations were selectively reduced in the dentate gyrus 20 h following amphetamine treatment. This effect did not persist through the four week withdrawal period. In separate experiments, rats received bromodeoxyuridine to label cells in S-phase, prior to or immediately following amphetamine treatment. Newly generated cells were quantified to measure extent of progenitor cell proliferation and neurogenesis following treatment or withdrawal. Progenitor cell proliferation and neurogenesis were not significantly affected by amphetamine exposure when measured 20 h following the last amphetamine treatment. However, neurogenesis in the dentate gyrus was reduced after four weeks of withdrawal when compared to saline-pretreated rats. Overall, our findings indicate that withdrawal from chronic amphetamine leads to persistent anxiety-like behavior which may be maintained by reduced neurogenesis in the dentate gyrus at this protracted withdrawal time point. However, neurogenesis is unaffected at earlier withdrawal time points where anxiety states emerge, suggesting different mechanisms may underlie the emergence of anxiety states during amphetamine withdrawal.

Effect of systemic matrix metalloproteinase inhibition on periodontal wound repair: a proof of concept trial

BACKGROUND

The adjunctive use of matrix metalloproteinase (MMP) inhibitors with scaling and root planing (SRP) promotes new attachment in patients with periodontal disease. This pilot study was designed to examine aspects of the biological response brought about by the MMP inhibitor low dose doxycycline (LDD) combined with access flap surgery (AFS) on the modulation of periodontal wound repair in patients with severe chronic periodontitis.

METHODS

Twenty-four subjects were enrolled into a 12-month, randomized, placebo-controlled, double-masked trial to evaluate clinical, biochemical, and microbial measures of disease in response to 6 months therapy of either placebo capsules + AFS or LDD (20 mg b.i.d.) + AFS. Clinical measures including probing depth (PD), clinical attachment levels (CAL), and bleeding on probing (BOP) as well as gingival crevicular fluid bone marker assessment (ICTP) and microbial DNA analysis (levels and proportions of 40 bacterial species) were performed at baseline and 3, 6, 9, and 12 months.

RESULTS

Patients treated with LDD + AFS showed more potent reductions in PD in surgically treated sites of >6 mm (P<0.05, 12 months). Furthermore, LDD + AFS resulted in greater reductions in ICTP levels compared to placebo + AFS. Rebounds in ICTP levels were noted when the drug was withdrawn. No statistical differences between the groups in mean counts were found for any pathogen tested.

CONCLUSIONS

This pilot study suggests that LDD in combination with AFS may improve the response of surgical therapy in reducing probing depth in severe chronic periodontal disease. LDD administration also tends to reduce local periodontal bone resorption during drug administration. The use of LDD did not appear to contribute to any significant shifts in the microbiota beyond that of surgery alone.

Creating a vision for your medical call center

MCC technologies and applications that can have a positive impact on managed care delivery are almost limitless. As you determine your vision, be sure to have in mind the following questions: (1) Do you simply want an efficient front end for receiving calls? (2) Do you want to offer triage services? (3) Is your organization ready for a fully functional "electronic physician's office?" Understand your organization's strategy. Where are you going, not only today but five years from now? That information is essential to determine your vision. Once established, your vision will help determine what you need and whether you should build or outsource. Vendors will assist in cost/benefit analysis of their equipment, but do not lose sight of internal factors such as "prior inclination" costs in the case of a nurse triage program. The technology is available to take your vision to its outer reaches. With the projected increase in utilization of call center services, don't let your organization be left behind!

Interference with testing for lysergic acid diethylamide

We found a high rate (4.2%) of positive results for lysergic acid diethylamide (LSD) by Emit in 1898 urine samples that were submitted primarily from psychiatric patients for drugs-of-abuse (DOA) testing. Specimens that tested positive for LSD by Emit subsequently tested negative for LSD with two RIAs. Furthermore, LSD was not detected in randomly selected Emit-positive urine samples by gas chromatography-mass spectrometry. Normal urine samples tested positive for LSD by Emit when they were supplemented with therapeutic medications that were prescribed for patients with positive urine LSD results by Emit. These therapeutic drugs interfered specifically with the Emit assay for LSD, since other Emit DOA tests were not affected by these medications at the tested concentrations.

Familial carriage of methicillin-resistant Staphylococcus aureus and subsequent infection in a premature neonate

During routine surveillance of patients in a Neonatal Intensive Care Unit (NICU), an alert infection-control practitioner confirmed the relationship of the index patient (sibling 3) who had a methicillin-resistant Staphylococcus aureus (MRSA) infection to an infant sibling (sibling 2) who had been admitted to the hospital 7 months previously with an MRSA infection. Cultures of nasal specimens obtained from the index patient's parents and two other siblings also yielded MRSA for two of the family members, the mother and sibling 1. The strains were typed by antibiogram, plasmid analysis, and genomic DNA typing. The isolates from sibling 1, sibling 2, the mother, and one isolate from sibling 3 were found to be identical by all techniques. The other isolates from sibling 3 shared the same genomic type but had no detectable plasmids. These findings suggest that transmission of this strain occurred at least three times within this family and that at least one family member was colonized with the same strain for 7 months or more. Recognition that family members may serve as reservoirs for nosocomial infections with MRSA raises important issues for infection control.

Drug findings in 'Driving Under the Influence of Drugs' cases: a problem of illicit drug use

Drug findings in 137 drug positive cases of Driving Under the Influence of Drugs (DUID) occurring in St. Louis, Missouri, U.S.A. from June 1983 through May 1986 are presented. Thirty-two different drugs were detected. A single agent was detected in only 34% (47/137) of cases. The most frequently encountered drugs, expressed as percent of positive cases, were: phencyclidine, 47%; marijuana, 47%; benzodiazepines, 22%; barbiturates, 15%; opiates, 11%; and cocaine, 9%. Most multiple drug cases involved popular illicit drug mixtures, such as cocaine and morphine (speedballs) or phencyclidine on marijuana (whack). All the drivers in this survey had displayed inappropriate or impaired operation of a motor vehicle to the extent that a law enforcement officer had stopped and charged them for DUID. In at least 81% of the drug positive cases, persons impaired in the operation of a motor vehicle from a drug or drugs other than alcohol, were impaired not as the result of side effects of therapeutic drug use, but as the result of deliberate self intoxication with illicit or controlled substances.

Tissue disposition of cocaine in man: a report of five fatal poisonings

The disposition of cocaine in five cases of fatal poisoning are presented. The highest concentrations of cocaine were found in urine, kidney, spleen, brain, lung and skeletal muscle. Cocaine concentrations in these organs far exceeded those in blood. Cocaine was detected in all other specimens tested including: bile, heart, liver, vitreous and adipose tissue. These results are in agreement with limited, previously reported, tissue data, and indicate that when urine is not available, kidney, spleen, brain and/or lung should be the specimen of choice for cocaine detection.