Drug Re-exposure Research Articles

Radiation recall reaction induced by gemcitabine/docetaxel in children: A retrospective study on risk factors and outcomes.

Radiation recall reaction (RRR) is a rare inflammatory reaction developing in a previously irradiated field after a triggering agent. In pediatric patients, it is poorly understood and deficiently studied. Gemcitabine-docetaxel (G/D) in childhood cancer is mainly used as a salvage regimen for sarcomas. We aim to describe RRR triggered by G/D in children. Retrospective review of 21 patients receiving G/D along with radiotherapy at two hospitals from 2010 until 2022. RRR was considered as any toxicity occurring after G/D administration in a previously irradiated field. RRR features were described. Fisher's and Mann-Whitney tests were utilized to analyze the risk factors involved. Sixteen episodes of RRR developed in 16 (76.2%) patients. RRR mainly involved deep layers of the skin (58%) and occurred predominantly after two G/D cycles. The mean time between radiotherapy and chemotherapy was 28.5days (0-1359days), and the mean radiation volume 391mL (157-1810mL) for RRR. RRR treatment was mainly systemic steroids, with partial responses in six of 11 (58%) patients. Re-exposure to G/D was associated with a high rate of recurrence in nine of 15 (56.2%), prompting drug discontinuation. The major risk factors for RRR after G/D include, without statistical significance, a larger volume of the irradiated field and a shorter interval between chemotherapy and radiotherapy. The incidence of RRR after G/D in the pediatric population is higher than previously reported. Drug re-exposure is usually followed by recurrence. Higher irradiated volumes and a shorter time to the start of chemotherapy could be related with an increased risk of RRR.

Differential cytokine profiles produced by anti-epileptic drug re-exposure of peripheral blood mononuclear cells derived from severe anti-epileptic drug patients and non-allergic controls

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and drug reactions with eosinophilia and systemic symptoms (DRESS) are the most common severe cutaneous adverse drug reactions (SCARs). Anti-epileptic drugs are one of the most common drugs causing SCARs. Cytokine profiles of SCARs during culprit drug exposure have never been characterized. This study aimed to identify cytokine patterns between SCARs and non-SCARs in epilepsy patients and the patterns of DRESS and SJS/TEN. Epilepsy patients that showed allergic responses to anti-epileptic drugs that manifested as SJS/TEN or DRESS were recruited. Epilepsy patients with no drug allergy symptoms and healthy people were also recruited as control groups. Peripheral blood mononuclear cells (PBMCs) were isolated and co-cultured with assigned anti-epileptic drugs according to the lymphocyte transformation test (LTT). LTT and measurement of cytokine levels in supernatants were performed on day six of cell cultivation. This study identified different cytokine expression patterns between SCAR and non-SCAR in epilepsy patients. Significant levels of IL-10, IL-12, IL-17, and GM-CSF were detected in non-SCAR epilepsy. However, the levels of IL-2, IL-5, IL-13, and IFN-gamma were significantly higher in supernatants of PBMCs of DRESS cultivated with AEDs relative to those of SJS/TEN. These cytokine levels were positively correlated with the cell proliferation index. Production of IL-5 and IL-13 was a unique characteristic of DRESS PBMCs. This study was the first to demonstrate distinct differences in cytokine levels between SCAR and non-SCAR PBMCs in epilepsy, which could help explain the immune-pathomechanism of drug hypersensitivity in SCARs. Different patterns of cytokine production and cell proliferation between DRESS and SJS/TEN in AED hypersensitivity were also demonstrated. Production of IL-5 and IL-13 might be a promising marker to define drug hypersensitivity in DRESS.

Drug reexposure in children with severe mucocutaneous reactions.

In pediatric patients, severe cutaneous adverse reactions (SCARs) frequently occur in the course of acute illnesses, mostly infections, which are usually treated with antibiotics or analgesics. The drug provocation test (DPT) is contraindicated in such situations, due to the risk of triggering a new severe reaction. As a consequence, lifelong avoidance is recommended. However, causation is uncertain in most cases. The dilemma arises when avoiding the drug is not harmless for the patient. We have attended three patients who were referred to our pediatric allergy unit with a history of SCAR related in time to simultaneous use of paracetamol and ibuprofen. Medical records and images of the patients were reviewed with the assistance of a dermatologist, and alternative diagnoses were considered in both cases. The ALDEN score for implicated drugs was calculated. After considering a high probability of ibuprofen tolerance and obtaining informed consent from the patients, we performed a sequential allergy workup including in vitro tests, skin tests, and finally DPT in two of the patients, confirming ibuprofen tolerance. In conclusion, although generally contraindicated, DPT may be considered for some useful drugs after careful evaluation of the risk-benefit balance, preceded by a sequential study including in vitro and skin tests.

Early high-dose intravenous corticosteroids rapidly arrest Stevens Johnson syndrome and drug reaction with eosinophilia and systemic symptoms recurrence on drug re-exposure

Early high-dose intravenous corticosteroids rapidly arrest Stevens Johnson syndrome and drug reaction with eosinophilia and systemic symptoms recurrence on drug re-exposure

Plasticity of Drug-Naïve and Vemurafenib- or Trametinib-Resistant Melanoma Cells in Execution of Differentiation/Pigmentation Program.

Melanoma plasticity creates a plethora of opportunities for cancer cells to escape treatment. Thus, therapies must target all cancer cell subpopulations bearing the potential to contribute to disease. The role of the differentiation/pigmentation program in intrinsic and acquired drug resistance is largely uncharacterized. MITF level and expression of MITF-dependent pigmentation-related genes, MLANA, PMEL, TYR, and DCT, in drug-naïve and vemurafenib- or trametinib-treated patient-derived melanoma cell lines and their drug-resistant counterparts were analysed and referred to genomic alterations. Variability in execution of pigmentation/differentiation program was detected in patient-derived melanoma cell lines. Acute treatment with vemurafenib or trametinib enhanced expression of pigmentation-related genes in MITF-Mhigh melanoma cells, partially as the consequence of transcriptional reprograming. During development of resistance, changes in pigmentation program were not unidirectional, but also not universal as expression of different pigmentation-related genes was diversely affected. In selected resistant cell lines, differentiation/pigmentation was promoted and might be considered as one of drug-tolerant phenotypes. In other resistant lines, dedifferentiation was induced. Upon drug withdrawal (“drug holiday”), the dedifferentiation process in resistant cells either was enhanced but reversed by drug reexposure suggesting involvement of epigenetic mechanisms or was irreversible. The irreversible dedifferentiation might be connected with homozygous loss-of-function mutation in MC1R, as MC1RR151C +/+ variant was found exclusively in drug-naïve MITF-Mlow dedifferentiated cells and drug-resistant cells derived from MITFhigh/MC1RWT cells undergoing irreversible dedifferentiation. MC1RR151C +/+ variant might be further investigated as a parameter potentially impacting melanoma patient stratification and aiding in treatment decision.

Cell-type and region-specific nucleus accumbens AMPAR plasticity associated with morphine reward, reinstatement, and spontaneous withdrawal.

Despite evidence that morphine-related pathologies reflect adaptations in NAc glutamate signaling, substantial gaps in basic information remain. The current study examines the impact of non-contingent acute, repeated, and withdrawal-inducing morphine dosing regimens on glutamate transmission in D1- or D2-MSNs in the nucleus accumbens shell (NAcSh) and core (NAcC) sub-regions in hopes of identifying excitatory plasticity that may contribute tounique facets of opioid addiction-related behavior. Following an acute morphine injection (10mg/kg), average miniature excitatory postsynaptic current (mEPSC) amplitude mediated by AMPA-type glutamate receptors was increased at D1-MSNs in the both the NAcShl and NAcC, whereas only the frequency of events was elevated at D2-MSNs in the NAcSh. In contrast, spontaneoussomatic withdrawal induced by escalating dose of repeated morphine twice per day (20, 40, 60, 80, 100mg/kg) enhanced mEPSC frequency specifically atD2-MSNs in the NAcSh. Similar to previous findings, excitatory drive was elevated at NAcSh D1-MSNs after10-14dayshome cage abstinence. Following abstinence, an acute drug re-exposureproduced a rapid and enduring endocytosis of GluA2-containing AMPARs at D1-MSNs in the shell, that when blocked by an intra-NAc shell infusion of the Tat-GluA23Y peptide, increased reinstatement of morphine place preference-a phenomenon distinctly different than effects previously found with cocaine. The present study is the first to directly identify unique circuit specific adaptations in NAc glutamate synaptic transmission associated with morphine-related acute reward and somatic withdrawal as well as post-abstinence short-term plasticity. Moreover,while differing classes of abused drugs (i.e., psychostimulants and opioids) produce seemingly similar bidirectional plasticity in the NAc following drug re-exposure, our findings indicate this plasticity has distinct behavioral consequences.

Short and extended provocation tests have similar negative predictive value in non-immediate hypersensitivity to beta-lactams in children

Introduction and objectivesDrug provocation tests (DPTs) are the gold-standard method to diagnose non-immediate hypersensitivity reactions (NIHSR) to beta-lactam antibiotics (BL) in children. Our aim was to compare the negative predictive value (NPV) of one-day (short) DPT versus 3–7 days (extended) DPT for the diagnosis of NIHSR to BL in paediatric age. A secondary aim was to compare confidence on drug re-exposure after short and extended negative DPTs. MethodsThe occurrence of HSR on drug re-exposure and drug refusal after negative diagnostic DPTs were evaluated in children/adolescents with a history of NIHSR to BL using a questionnaire performed six months to ten years after DPT. Patients were divided into two groups according to the protocol performed: short DPT vs. extended DPT. ResultsWe enrolled 212 children and adolescents (86 females, 126 males, mean age at DPT 5.52 years, p25=3 years, p75=7.25 years): 69 tested with short DPT, and 143 with extended DPT. The NPV of both types of DPT together was 95.2%. The NPV of short DPT was 97.5% and the NPV of extended DPT was 93.8% (p=0.419). After negative DPT, beta-lactams were refused by carers in 14.75% of the children requiring subsequent treatment, 6.98% in the short DPT group and 18.99% in the extended DPT group (p=0.074). ConclusionsIn our paediatric sample, prolonging drug administration did not increase the NPV of diagnostic DPT for NIHSR to BL or reduce drug refusal. Altogether, the data here reported suggest that, however intuitive, prolonging DPT is not beneficial in the parameters analysed.

Adolescent cocaine exposure enhanced negative affect following drug re-exposure in adult rats: Attenuation of c-Fos activation.

The goal of the present study was to utilize the adolescent drug experience as an emerging vulnerability factor for developing psychiatric comorbidities in adulthood that could, in turn, help to elucidate and/or hypothesize possible mechanisms contributing to higher relapse rates. The current results showed that adolescent cocaine exposure (15 mg/kg, intraperitoneally, seven days) during early-mid adolescence (postnatal days 33-39) enhanced negative affect in adulthood, by increasing behavioral despair following drug re-exposure and by increasing anhedonia. Thus, these behavioral data provided a good model to further ascertain the long-term cellular and molecular adaptations that might take place in the brain in response to adolescent cocaine exposure as well as the impact of drug re-exposure in adulthood. In this regard, the results showed that adolescent cocaine exposure did not modulate cell proliferation (Ki-67+ cells) or c-Fos protein activation in the dentate gyrus region of the hippocampus, but attenuated c-Fos activation in the dorsal striatum. These results proved that a history of cocaine exposure during adolescence increased the vulnerability to induce negative affect (i.e. emergence of psychiatric comorbidity) in adulthood while it decreased neuronal activation in the dorsal striatum. Interestingly, these effects were only observed following cocaine re-exposure in adulthood, suggesting that avoiding drug contact in adulthood could prevent the long-term negative effects induced by adolescent cocaine.

Intra-hippocampal administration of orexin receptor antagonists dose-dependently attenuates reinstatement of morphine seeking behavior in extinguished rats

It has been shown that the hippocampus plays an essential role in the regulation of reward and memory as indicated by the conditioned place preference (CPP) paradigm. Morphine-induced CPP is a common method to consider motivational properties of morphine in animals. Recently, this model has been used in many laboratories to investigate neuronal mechanisms underlying reinstatement of morphine seeking induced by drug re-exposure. Our previous studies indicate that the hippocampus especially CA1 region is involved in reinstatement of drug-seeking behaviors. Also, several studies have shown that orexin attenuates key functional and behavioral effects of its co-transmitter dynorphin. The present study evaluates the role of orexinergic receptors within the CA1 region of the hippocampus in the reinstatement of morphine-induced CPP. Therefore, after the extinction period, the different doses (SB 334867; 0.3, 3, and 30 nM/0.5 μl DMSO) of either orexin-1 or -2 receptor antagonists were bilaterally microinjected into the CA1, 15 min before receiving an effective priming dose of morphine (1 mg/kg). The results revealed that administration of both SB 334867 and TCS OX2 29 prior to injection of the priming dose of morphine significantly reduced the reinstatement of morphine-induced CPP without altering the animal's locomotor activity. Also, the 50% effective dose value of SB 334867 on the reinstatement of morphine seeking behavior was close three times more than that in TCS OX2 29 treatment group. Therefore, the consequences suggested that both orexin receptors in the CA1 play a considerable role in the reinstatement of morphine-induced CPP.

Trombocitopenia inducida por rifampicina

Rifampicin-induced thrombocytopenia is a rare but potentially fatal immune phenomenon. We report the case of an immunocompromised patient with disseminated tuberculosis who developed rifampicin-induced thrombocytopenia 12 hours after starting anti-tuberculous therapy without previous drug sensitization. The cause-effect relationship was confirmed when thrombocytopenia resolved with rifampicin suspension but later reappeared upon drug re-exposure.

Managing immune checkpoint-inhibitor-induced severe autoimmune-like hepatitis by liver-directed topical steroids.

3073 Background: The CTLA4-antibody ipilimumab, and PD-1-antibodies pembrolizumab as well as nivolumab have revolutionized antineoplastic therapies. Induction of autoimmune-like drug-induced liver injury (DILI) is within the spectrum of adverse reactions of these new drugs and has been observed in about 1-5 % of patients, developing predominantly within the first 6 to 12 weeks after start of treatment. Immediate application of systemic steroids and a permanent discontinuation of immune checkpoint-inhibition therapy are recommended for any alanine aminotransferase increase ≥ WHO grade 3. In severe autoimmune-like DILI the permanent discontinuation of the immune checkpoint inhibitor is recommended, as drug re-exposure might be associated with a significant risk of a fulminant DILI. Methods: We report six patients with severe grade 3 autoimmune-like DILI (according to Common Terminology Criteria for Adverse Events 4.3) treated with long-term application of budesonide, a liver-directed topical steroid. Results: Immune checkpoint inhibitors were stopped and methylprednisolone was applied initially with a dose of 1 mg/kg body weight and tapered thereafter. To reduce systemic steroids and to minimize the exposure time to systemic steroids, the topical steroid budesonide 3 mg three times per day was additionally given in combination with N-acetylcysteine and ursodeoxycholic acid. Under this multimodal approach transaminases normalized and the respective immune-checkpoint inhibitor could be re-started without re-manifestation of DILI under the continuous treatment with budesonide. Conclusions: Budesonide - a liver-directed topical steroid - might be an interesting approach to target liver related autoimmune adverse reactions induced by immune checkpoint inhibitors without compromising their anti-cancer effect. We were able to safely and effectively re-introduce and continue immune checkpoint inhibitors under the continuous application of the topical steroid without showing any further liver toxicity.

LO91: Repeat exposures to culprit drugs contribute to adverse drug events in emergency department patients

Introduction: Adverse drug events (ADEs), unintended and harmful events associated with medications, cause or contribute to 2 million annual emergency department (ED) visits in Canada. Australian data indicate that 27% of ADEs requiring admission are events caused by re-exposure to drugs that previously caused harm. Our objective was to estimate the frequency of repeat ADEs. Methods: We reviewed the charts of ADE patients who had been enrolled in 1 of 3 prospective studies conducted in 2 tertiary care and 1 urban community ED. In the parent studies, researchers enrolled patients by applying a systematic selection algorithm to minimize selection bias, and physicians and pharmacists evaluated patients prospectively to evaluate the causal association between the drug regimens and patient presentations. After completion of the parent studies, a research pharmacist and a physician independently reviewed the charts of ADE patients, abstracted data using electronic forms, and searched that hospital’s records for previously recorded ADEs. The main outcome was a repeat ADE, defined as a same or same-class drug re-exposure, or repeat inappropriate drug withdrawal, causing a same or similar presentation as a prior ADE. Sample size was based on enrolment into the parent studies. Results: We reviewed the charts of 614 ED patients diagnosed with 655 ADEs. Of these, 20% (133/665, 95%CI 17.0-23.0%) were repeat events. Most repeat ADEs were moderate (61%) or severe (32%) in nature, and 33% (95%CI 25.1-41.1%) required hospital admission. The most commonly implicated drugs were warfarin (10%), hydrochlorothiazide (4%) and insulin (4%), and the most commonly implicated drug classes were antithrombotics (17%), psychotropics (12%) and analgesics (9%). Repeat ADEs commonly required clinical monitoring (59%), additional medications to treat the ADE (50%) and follow-up lab testing (35%). Overall, 61% (95%CI 51.3-70.7%) of culprit drug re-exposures were deemed potentially or definitely inappropriate. Conclusion: Inappropriate re-exposures to previously harmful medications cause a substantial number of recurrent ADEs, and may represent an ideal target for prevention. We were unable to search for repeat ADEs in the records of other hospitals that our patients may have visited, and could not detect ADEs that were not documented in the medical record. As a result, we likely underestimated the frequency of repeat ADEs.

Cocaine Self-Administration Produces Long-Lasting Alterations in Dopamine Transporter Responses to Cocaine.

Cocaine addiction is a debilitating neuropsychiatric disorder characterized by uncontrolled cocaine intake, which is thought to be driven, at least in part, by cocaine-induced deficits in dopamine system function. A decreased ability of cocaine to elevate dopamine levels has been repeatedly observed as a consequence of cocaine use in humans, and preclinical work has highlighted tolerance to cocaine's effects as a primary determinant in the development of aberrant cocaine taking behaviors. Here we determined that cocaine self-administration in rats produced tolerance to the dopamine transporter-inhibiting effects of cocaine in the nucleus accumbens core, which was normalized following a 14 or 60 d abstinence period; however, although these rats appeared to be similar to controls, a single self-administered infusion of cocaine at the end of abstinence, even after 60 d, fully reinstated tolerance to cocaine's effects. A single cocaine infusion in a naive rat had no effect on cocaine potency, demonstrating that cocaine self-administration leaves the dopamine transporter in a "primed" state, which allows for cocaine-induced plasticity to be reinstated by a subthreshold cocaine exposure. Further, reinstatement of cocaine tolerance was accompanied by decreased cocaine-induced locomotion and escalated cocaine intake despite extended abstinence from cocaine. These data demonstrate that cocaine leaves a long-lasting imprint on the dopamine system that is activated by re-exposure to cocaine. Further, these results provide a potential mechanism for severe cocaine binge episodes, which occur even after sustained abstinence from cocaine, and suggest that treatments aimed at transporter sites may be efficacious in promoting binge termination following relapse. Tolerance is a DSM-V criterion for substance abuse disorders. Abusers consistently show reduced subjective effects of cocaine concomitant with reduced effects of cocaine at its main site of action, the dopamine transporter (DAT). Preclinical literature has shown that reduced cocaine potency at the DAT increases cocaine taking, highlighting the key role of tolerance in addiction. Addiction is characterized by cycles of abstinence, often for many months, followed by relapse, making it important to determine possible interactions between abstinence and subsequent drug re-exposure. Using a rodent model of cocaine abuse, we found long-lasting, possibly permanent, cocaine-induced alterations to the DAT, whereby cocaine tolerance is reinstated by minimal drug exposure, even after recovery of DAT function over prolonged abstinence periods.

Ibudilast attenuates expression of behavioral sensitization to cocaine in male and female rats

There are no FDA-approved pharmacotherapies for cocaine use disorder, indicating a need to identify novel reagents with therapeutic potential. Ibudilast is an anti-inflammatory glial attenuator and non-selective phosphodiesterase inhibitor currently undergoing clinical evaluations for methamphetamine, opiate, and alcohol abuse disorders. We previously showed that twice daily (b.i.d.) ibudilast reduces the development of methamphetamine sensitization in male mice. However, nothing is known about the ability of ibudilast to modulate the expression of sensitization that occurs after drug re-exposure during abstinence, effects on cocaine-mediated behaviors, or potentially sexually dimorphic effects. Male and female rats were administered cocaine for 7 days and expression of sensitization was assessed by cocaine challenge after 21 days abstinence. On test days, 15 mg/kg i. p. cocaine was evaluated, whereas 30 mg/kg was administered on intervening days. Lower test doses avoid competition of non-motor behaviors with locomotion. In all measures where sensitization was expressed, ibudilast (7.5 and 10 mg/kg, i. p., b. i.d. for 3 days and once on test day) reversed this behavior to levels seen after acute exposure, but not below. There were some intriguing sexually dimorphic effects that were not a function of estrous cycle. Specifically, distance travelled in the center of the test arena and rearing only sensitized in male rats, and ibudilast reversed these behaviors to levels seen after acute cocaine exposure. In females, center distance travelled was reduced below acute cocaine levels by 7.5 mg/kg ibudilast. Increased distance travelled in the center versus periphery is thought to model anxiolytic-like behavior due to increased predation risk. Taken together, these data suggest that the clinical evaluation of ibudilast could be extended to cocaine use disorder.

Repeated exposure to amphetamine during adolescence alters inhibitory tone in the medial prefrontal cortex following drug re-exposure in adulthood

Behavioral sensitization following repeated amphetamine (AMPH) exposure is associated with changes in GABA function in the medial prefrontal cortex (mPFC). In rats exposed to AMPH during adolescence compared to adulthood, there are unique patterns of sensitization that may reflect age-dependent differences in drug effects on prefrontal GABAergic function. In the current study, we used a sensitizing regimen of repeated AMPH exposure in adolescent and adult rats to determine if a post-withdrawal AMPH challenge would alter inhibitory transmission in the mPFC in a manner that depends on age of exposure. Male Sprague-Dawley rats were treated with saline or 3mg/kg AMPH (i.p.) during adolescence [postnatal day (P) 27–P45] or adulthood (P85– P103) and were sacrificed either at similar ages in adulthood (∼P133; experiment 1) or after similar withdrawal times (3–4 weeks; experiment 2). Spontaneous inhibitory postsynaptic currents (sIPSCs) were recorded in vitro from deep layer pyramidal cells in the mPFC using the whole-cell configuration. We found no effect of AMPH pre-exposure on baseline sIPSC frequency. Subsequent application of AMPH (25μM) produced a stable increase in sIPSC frequency in controls, suggesting that AMPH increases inhibitory tone in the mPFC. However, AMPH failed to increase sIPSCs in adolescent- or adult-exposed rats. In experiment 2, where withdrawal period was kept similar for both exposure groups, AMPH induced a suppression of sIPSC activity in adolescent-exposed rats. These results suggest that sensitizing treatment with AMPH during adolescence or adulthood dampens inhibitory influences on mPFC pyramidal cells, but potentially through different mechanisms.

L-type Ca²⁺ channel blockade with antihypertensive medication disrupts VTA synaptic plasticity and drug-associated contextual memory.

Drug addiction is driven, in part, by powerful and enduring memories of sensory cues associated with drug intake. As such, relapse to drug use during abstinence is frequently triggered by an encounter with drug-associated cues, including the drug itself. L-type Ca2+ channels (LTCCs) are known to regulate different forms of synaptic plasticity, the major neural substrate for learning and memory, in various brain areas. Long-term potentiation (LTP) of NMDA receptor (NMDAR)-mediated glutamatergic transmission in the ventral tegmental area (VTA) may contribute to the increased motivational valence of drug-associated cues triggering relapse. In this study, using rat brain slices, we found that isradipine, a general LTCC antagonist used as antihypertensive medication, not only blocks the induction of NMDAR LTP but also promotes the reversal of previously induced LTP in the VTA. In behaving rats, isradipine injected into the VTA suppressed the acquisition of cocaine-paired contextual cue memory assessed using a conditioned place preference (CPP) paradigm. Furthermore, administration of isradipine or a CaV1.3 subtype-selective LTCC antagonist (systemic or intra-VTA) before a single extinction or reinstatement session, while having no immediate effect at the time of administration, abolished previously acquired cocaine and alcohol (ethanol) CPP on subsequent days. Notably, CPP thus extinguished cannot be reinstated by drug re-exposure, even after 2 weeks of withdrawal. These results suggest that LTCC blockade during exposure to drug-associated cues may cause unlearning of the increased valence of those cues, presumably via reversal of glutamatergic synaptic plasticity in the VTA.

Adolescent olanzapine sensitization is correlated with hippocampal stem cell proliferation in a maternal immune activation rat model of schizophrenia

Previous work established that repeated olanzapine (OLZ) administration in normal adolescent rats induces a sensitization effect (i.e. increased behavioral responsiveness to drug re-exposure) in the conditioned avoidance response (CAR) model. However, it is unclear whether the same phenomenon can be detected in animal models of schizophrenia. The present study explored the generalizability of OLZ sensitization from healthy animals to a preclinical neuroinflammatory model of schizophrenia in the CAR. Maternal immune activation (MIA) was induced via polyinosinic:polycytidylic acid (PolyI:C) administration into pregnant dams. Behavioral assessments of offspring first identified decreased maternal separation-induced pup ultrasonic vocalizations and increased amphetamine-induced hyperlocomotion in animals prenatally exposed to PolyI:C. In addition, repeated adolescent OLZ administration confirmed the generalizability of the sensitization phenomenon. Using the CAR test, adolescent MIA animals displayed a similar increase in behavioral responsiveness after repeated OLZ exposure during both the repeated drug test days as well as a subsequent challenge test. Neurobiologically, few studies examining the relationship between hippocampal cell proliferation and survival and either antipsychotic exposure or MIA have incorporated concurrent behavioral changes. Thus, the current study also sought to reveal the correlation between OLZ behavioral sensitization in the CAR and hippocampal cell proliferation and survival. 5′-bromodeoxyuridine immunohistochemistry identified a positive correlation between the magnitude of OLZ sensitization (i.e. change in avoidance suppression induced by OLZ across days) and hippocampal cell proliferation. The implications of the relationship between behavioral and neurobiological results are discussed.

Amphetamine acts within the lateral hypothalamic area to elicit affectively neutral arousal and reinstate drug-seeking

Psychostimulants, including amphetamine (AMPH), exert robust arousal-enhancing, reinforcing and locomotor-activating effects. These behavioural actions involve drug-induced elevations in extracellular norepinephrine (NE) and dopamine (DA) within a variety of cortical and subcortical regions. The lateral hypothalamic area (LHA), including the lateral hypothalamus proper, perifornical area and adjacent dorsomedial hypothalamus, is implicated in appetitive- and arousal-related processes. The LHA is innervated by both NE and DA projections and systemically administered AMPH has been demonstrated to activate LHA neurons. Combined, these and other observations suggest the LHA may be a site of action in the behavioural effects of psychostimulants. To test this hypothesis, we examined the degree to which AMPH (10nmol, 25nmol) acts within the LHA to exert arousing, locomotor-activating and reinforcing actions in quietly resting/sleeping rats. Although intra-LHA AMPH robustly increased time spent awake, this occurred in the absence of pronounced locomotor activation or reinforcing actions, as measured in a conditioned place preference (CPP) paradigm. Arousing and stressful conditions or drug re-exposure can elicit relapse in humans and reinstate drug-seeking in animals. Given the LHA is also implicated in the reinstatement of drug-seeking behaviour, additional studies examined whether AMPH acts within the LHA to reinstate an extinguished CPP produced with systemic AMPH administration. Our results demonstrate that AMPH action within the LHA is sufficient to reinstate drug-seeking behaviour, as measured in this paradigm. Collectively, these observations demonstrate that psychostimulants act within the LHA to elicit affectively neutral arousal and reinstate drug-seeking behaviour.

High incidence of antibodies to protamine and protamine/heparin complexes in patients undergoing cardiopulmonary bypass

AbstractProtamine is routinely used to reverse heparin anticoagulation during cardiopulmonary bypass (CPB). Heparin interacts with protamine to form ultralarge complexes that are immunogenic in mice. We hypothesized that patients exposed to protamine and heparin during CPB will develop antibodies (Abs) to protamine/heparin (PRT/H) complexes that are capable of platelet activation. Specimens from a recently completed prospective clinical trial (HIT [for heparin-induced thrombocytopenia] 5801 study; n = 500) of CPB patients were examined for PRT/H Abs at baseline, at time of hospital discharge (between days 3 through 7), and 30 days after CPB. PRT/H antibody features were characterized and correlated with adverse cardiovascular outcomes. We found a high incidence of PRT/H antibody formation (29%) in patients undergoing cardiac surgery. PRT/H Abs were of high titer (mean titer 1:14 744), showed heparin-dependent binding, and activated platelets in the presence of protamine. PRT/H Abs showed no cross-reactivity to platelet factor 4/heparin complexes, but were cross-reactive with protamine-containing insulin preparations. In the absence of circulating antigen at day 30, there were no complications of thrombocytopenia, thrombotic events, or long-term cardiovascular events. These studies show that Abs to PRT/H occur commonly after cardiac bypass surgery, share a number of serologic features with HIT Abs, including platelet activation, and may pose health risks to patients requiring drug reexposure.

Adolescent morphine exposure affects long-term microglial function and later-life relapse liability in a model of addiction.

Adolescence in humans represents a unique developmental time point associated with increased risk-taking behavior and experimentation with drugs of abuse. We hypothesized that exposure to drugs of abuse during adolescence may increase the risk of addiction in adulthood. To test this, rats were treated with a subchronic regimen of morphine or saline in adolescence, and their preference for morphine was examined using conditioned place preference (CPP) and drug-induced reinstatement in adulthood. The initial preference for morphine did not differ between groups; however, rats treated with morphine during adolescence showed robust reinstatement of morphine CPP after drug re-exposure in adulthood. This effect was not seen in rats pretreated with a subchronic regimen of morphine as adults, suggesting that exposure to morphine specifically during adolescence increases the risk of relapse to drug-seeking behavior in adulthood. We have previously established a role for microglia, the immune cells of the brain, and immune molecules in the risk of drug-induced reinstatement of morphine CPP. Thus, we examined the role of microglia within the nucleus accumbens of these rats and determined that rats exposed to morphine during adolescence had a significant increase in Toll-like receptor 4 (TLR4) mRNA and protein expression specifically on microglia. Morphine binds to TLR4 directly, and this increase in TLR4 was associated with exaggerated morphine-induced TLR4 signaling and microglial activation in rats previously exposed to morphine during adolescence. These data suggest that long-term changes in microglial function, caused by adolescent morphine exposure, alter the risk of drug-induced reinstatement in adulthood.