Evidence of polystyrene nanoplastic contamination and potential impacts in Mya arenaria clams in the Saint-Lawrence estuary (Canada).

Plastic materials found in the environment are expected to degrade into smaller plastic nanoparticles (NPs) posing a greater toxic risk because they sorb contaminants and pass physiological barriers. Moreover the presence and effects of NPs is difficult to tease out from the contamination background at polluted sites. The purpose of this study was to examine for the presence of polystyrene NPs in feral Mya arenaria clam population near anthropogenic sources of pollution and potential toxic effects. Polystyrene NPs were determined by a newly developed fluorescence-based and size exclusion chromatography methodologies. Clam health status was determined by following changes in air survival time, condition factor, growth, alcohol/aldehyde dehydrogenase (AADH), protein aggregation and lactate dehydrogenase (LDH). In addition, multi-elemental analysis in tissues was also determined. The results revealed that clams collected at 2 polluted sites contained elevated amounts of polystyrene-like NPs between 10 and 110 nm in size based on size exclusion chromatography. Elevated levels of AADH suggest the presence of hydroxylated products and were correlated with plastic NPs in tissues. Moreover, principal component analysis revealed that As, Ca, Cu, Sn and V were closely related to either polystyrene-like NPs in tissues or AADH activity. Although we cannot rule out other pollutants, clams contaminated by polystyrene-like NPs had lower condition, growth rate, air survival time and LDH activity. Increased metal/element contamination reported to sorb onto plastic polymers were also related to NPs in tissues. In conclusion, clams populations close to anthropogenic sources of pollution show evidence of polystyrene-like NPs contamination and could contribute to decreased clam health status.

Quantitative PCR reveals the frequency and distribution of 3 indigenous yeast species across a range of specialty cheeses.

Indigenous microorganisms are important components of the complex ecosystem of many dairy foods including cheeses, and they are potential contributors to the development of a specific cheese's sensory properties. Among these indigenous microorganisms are the yeasts Cyberlindnera jadinii, Pichia kudriavzevii, and Kazachstania servazzii, which were previously detected using traditional microbiological methods in both raw milk and some artisanal specialty cheeses produced in the province of Québec, Canada. However, their levels across different cheese varieties are unknown. A highly specific and sensitive real-time quantitative PCR assay was developed to quantitate these yeast species in a variety of specialty cheeses (bloomy-rind, washed-rind, and natural-rind cheeses from raw, thermized, and pasteurized milks). The specificity of the quantitative PCR assay was validated, and it showed no cross-amplification with 11 other fungal microorganisms usually found in bloomy-rind and washed-rind cheeses. Cyberlindnera jadinii and P. kudriavzevii were found in the majority of the cheeses analyzed (25 of 29 and 24 of 29 cheeses, respectively) in concentrations up to 104 to 108 gene copies/g in the cheese cores, which are considered oxygen-poor environments, and 101 to 104 gene copies/cm2 in the rind. However, their high abundance was not observed in the same samples. Whereas C. jadinii was present and dominant in all core and rind samples, P. kudriavzevii was mostly present in cheese cores. In contrast, K. servazzii was present in the rinds of only 2 cheeses, in concentrations ranging from 101 to 103 gene copies/cm2, and in 1 cheese core at 105 gene copies/g. Thus, in the ecosystems of specialty cheeses, indigenous yeasts are highly frequent but variable, with certain species selectively present in specific varieties. These results shed light on some indigenous yeasts that establish during the ripening of specialty cheeses.

The Kessler Abbreviated Psychological Distress Scale (K6) in Canadian population surveys : Report on psychometric assessment practices and analysis of the performance of several reliability coefficients.

OBJECTIVES: The objective of Study 1 is to identify the psychometric assessment and reporting practices of authors who have analyzed data from the Kessler Abbreviated Psychological Distress Scale (K6), collected in Canadian population surveys. The goal of Study 2 is to compare the performance of six reliability coefficients estimated from K6 data. METHODS: In Study 1, 71 publications using the K6 were reviewed and synthesized using an analysis grid. In Study 2, analyses were performed to compare the performance of the alpha coefficient to five other reliability coefficients using data from the 2009-2010 and 2013-2014 Canadian Community Health Survey (CCHS). Specifically, we estimated all six coefficient values, as well as their confidence intervals, regarding all respondents and respondent subgroups. RESULTS: Out of the 71 publications identified in Study 1, only nine reported a reliability coefficient drawn from their own sample. Even though no condition essential to use of the alpha coefficient was mentioned, it was the only coefficient presented. In Study 2, the values of all the other coefficients were found to be higher than those of the alpha coefficient. Significant variations were found in some respondent subgroups. CONCLUSION: Existing recommendations for the use of reliability coefficients are poorly implemented. It behooves authors to provide more information in their manuscripts, thereby enabling assessment of the psychometric qualities of the K6. The presentation of reliability coefficients for relevant subgroups and confidence intervals must also become standard practice, so that results can be more precisely interpreted.

Smoothing temperature and ratio of casein to whey protein: Two tools to improve nonfat stirred yogurt properties.

Consumers are not always ready to compromise on the loss of texture and increased syneresis that nonfat stirred yogurts display compared with yogurts that contain fat. In this study, we investigated milk protein composition and smoothing temperature as a means to control nonfat yogurt microstructure, textural properties, and syneresis. Yogurts were prepared with different ratios of casein to whey protein (R1.5, R2.8, and R3.9). Yogurts were pumped through a smoothing pilot system comprising a plate heat exchanger set at 15, 20, or 25°C and then stored at 4°C until analysis (d 1, 9, and 23). Yogurt particle size and firmness were measured. Yogurt syneresis and water mobility were determined, respectively, by centrifugation and time domain low-frequency proton nuclear magnetic resonance (1H-LF-NMR). Increasing the smoothing temperature increased gel firmness and microgel (dense protein aggregates) sizes independently of the whey protein content. Also, yogurt microgel sizes changed with storage time, but the evolution pattern depended on protein ratio. Yogurt R1.5 showed the largest particles, and their sizes increased with storage, whereas R2.8 and R3.9 had smaller microgels, and R3.9 did not show any increase in microgel size during storage. Micrographs showed a heterogeneous gel with the empty area occupied by serum for R1.5, whereas R2.8 and R3.9 showed fewer serum zones and a more disrupted gel embedding microgels. Induced syneresis reduced with greater whey protein content and time of storage. This is in agreement with 1H-LF-NMR showing less bulk water mobility with increasing whey protein content during storage. However, 1H-LF-RMN revealed higher values of spontaneous serum separation during storage for R1.5 and R3.9 yogurts, whereas these were lower and stable for R2.8 yogurt. Microgels play an important structural role in yogurt textural attributes, and their characteristics are modulated by whey protein content and smoothing temperature. Optimization of these parameters may help improve nonfat stirred dairy gel.

Studying stirred yogurt microstructure using optical microscopy: How smoothing temperature and storage time affect microgel size related to syneresis.

A grainy texture and high syneresis are 2 defects in low-fat stirred yogurt that are often disliked by consumers. In this study, a rheometer controlling the shear rate and temperature was used to simulate the smoothing step of yogurt manufacture. Identical formulations containing whey protein isolate or whey protein concentrate were compared. After the yogurt milk underwent heat treatment, inoculation, and fermentation at 42°C, the yogurt was smoothed at 42°C (Y42) or 20°C (Y20) or during a cooling ramp from 42°C to 20°C (YR). Induced syneresis (serum expelled by centrifugation) was measured on d 3. Sizes of microgels (dense protein aggregates) were investigated on d 0, 4, and 7 by laser diffraction and by image analysis using optical microscopy. Optical microscopy was also used to characterize the reorganized protein network embedding microgels. The type of whey protein ingredient had only a slight effect on the induced syneresis of YR and Y20 treated yogurts, and the major effect came from the smoothing temperature. The Y42 treatment presented the highest induced syneresis; YR and Y20 had similar low induced syneresis values. Images showed a heterogeneous microstructure (large microgels, reorganized gel) and serum separation for Y42; the YR and Y20 networks were homogeneous. Both the image analyses and laser diffraction showed that the microgel size depended on the smoothing temperature. However, only the image analyses made it possible to identify a time dependency effect on microgel size during storage. The number of microgels >104 µm2 continued to increase over time, whereas the number of microgels <103 µm2 decreased. Microscopic observations were less destructive than laser diffraction and highlighted the presence of microgel aggregation during storage.

Short communication: Effect of stirring operations on changes in physical and rheological properties of nonfat yogurts during storage.

The rheological and physical properties of stirred yogurt depend on several parameters, including the mechanical stress caused by stirring, smoothing, and cooling conditions (duration, intensity, or temperature). However, the literature reports little information about the effects of mechanical stress from all of the stirring operations on changes in yogurt properties during storage. The aim of this study was to determine, by means of a technical scale unit, the combined effects of stirring in the yogurt vat, smoothing, and cooling on changes in the rheological properties of nonfat yogurt during storage at 4°C. The yogurt was standardized to 14% total solids, 0% fat, and 4% protein, and was stirred with a technical scale unit using 2 stirring durations (5 min or 10 min), 2 types of cooling systems (plate or tubular heat exchanger), and 2 smoothing temperatures (38°C for yogurts smoothed before cooling or 20°C for yogurts smoothed after cooling). All yogurts were stored for 22 d at 4°C, and we determined the combined effect of the stirring operations on changes in syneresis, apparent viscosity, firmness, consistency, and flow time. During storage, post-acidification was the same for all stirred yogurts and involved restructuring of the protein network, which resulted in an increase in all properties except syneresis, which decreased. The combined stirring operations did not modify changes in syneresis during yogurt storage but did affect flow time, viscosity, consistency, and firmness. Changes in flow time depended on smoothing temperature, and viscosity and consistency depended on the cooling system used. Firmness was the property most affected by all combined stirring operations during storage. Therefore, the technical scale unit was effective for quantifying the combined effects of stirring, smoothing, and cooling on changes in yogurt properties during storage. This study also confirmed that the restructuring of stirred yogurt depended on the mechanical stress that occurred during the stirring process.

Long-term in vitro degradation behaviour of Fe and Fe/Mg2Si composites for biodegradable implant applications.

The major drawback of Fe-based materials for biodegradable implant applications is their slow degradation rate. Addition of second phase particles into the Fe matrix can increase the degradation rate at the beginning of the corrosion process. However, so far, there is neither quantitative data on in vitro degradation nor direct experimental evidence for long-term dissolution of Fe-based biodegradable composites. Here, a series of immersion tests at different exposure intervals (20, 50 and 100 days) to modified Hanks' solution were performed to study the degradation behavior of Fe and Fe/Mg2Si composites prepared by different powder metallurgy techniques. The results revealed the role of Mg2Si in the composition and stability of the protective films formed during the static corrosion experiments. Fe/Mg2Si composites showed higher degradation rates than those of pure Fe at all stages of immersion. Degradation rates at distinct exposure intervals strongly depended on the composition and stability of formed oxide, hydroxide, carbonate and phosphate protective films on the degraded surfaces. The release of Fe ions into the solution at later stages of the experiment was limited due to the barrier effect of the insoluble deposit. This fundamental study provided a basis for the processes of protective film formation in modified Hanks' solution, which enables a detailed identification of its characteristic features.

Controlled Distribution and Clustering of Silver in Ag-DLC Nanocomposite Coatings Using a Hybrid Plasma Approach.

Incorporation of selected metallic elements into diamond-like carbon (DLC) has emerged as an innovative approach to add unique functional properties to DLC coatings, thus opening up a range of new potential applications in fields as diverse as sensors, tribology, and biomaterials. However, deposition by plasma techniques of metal-containing DLC coatings with well-defined structural properties and metal distribution is currently hindered by the limited understanding of their growth mechanisms. We report here a silver-incorporated diamond-like carbon coating (Ag-DLC) prepared in a hybrid plasma reactor which allowed independent control of the metal content and the carbon film structure and morphology. Morphological and chemical analyses of Ag-DLC films were performed by atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The vertical distribution of silver from the surface toward the coating bulk was found to be highly inhomogeneous due to top surface segregation and clustering of silver nanoparticles. Two plasma parameters, the sputtered Ag flux and ion energy, were shown to influence the spatial distribution of silver particles. On the basis of these findings, a mechanism for Ag-DLC growth by plasma was proposed.

[Study of microstructure of pectin and whey protein isolate mixtures under incompatible conditions using dynamic light scattering and transmission electron microscopy].

The microstructure of the pectin/whey protein isolate mixtures under incompatible conditions was investigated using dynamic light scattering spectroscopy, transmission electron microscopy and shear-viscosity model. Under the condition of 90 degrees C and pH 7.4, the presence of negatively charged pectin could induce depletion aggregation in a 5% protein solution, and promote phase separation; precisely, when the mass ratio of pectin/whey protein isolate was lower than 0.08, the hydrodynamic size of the aggregates was less than 300 nm, and the system showed Newtonian properties; when the mass ratio was higher than 0.08, the viscosity of the solution increased rapidly, the shear thinning properties became obvious and the size of the aggregates was close to 700 nm.

Development of an optimized electrochemical process for subsequent coating of 316 stainless steel for stent applications.

Metallic endovascular stents are used as medical devices to scaffold biological lumen, most often diseased arteries, after balloon angioplasty. They are commonly made of 316L stainless steel or Nitinol, two alloys containing nickel, an element classified as potentially toxic and carcinogenic by the International Agency for Research on Cancer. Although they are largely implanted, the long-term safety of such metallic elements is still controversial, since the corrosion processes may lead to the release of several metallic ions, including nickel ions in diverse oxidation states. To avoid metallic ion release in the body, the strategy behind this work was to develop a process aiming the complete isolation of the stainless steel device from the body fluids by a thin, cohesive and strongly adherent coating of RF-plasma-polymerized fluoropolymer. Nevertheless, prior to the polymer film deposition, an essential aspect was the development of a pre-treatment for the metallic substrate, based on the electrochemical polishing process, aiming the removal of any fragile interlayer, including the native oxide layer and the carbon contaminated layer, in order to obtain a smooth, defect-free surface to optimize the adhesion of the plasma-deposited thin film. In this work, the optimized parameters for electropolishing, such as the duration and the temperature of the electrolysis, and the complementary acid dipping were presented and accurately discussed. Their effects on roughness as well as on the evolution of surface topography were investigated by Atomic Force Microscopy, stylus profilometry and Scanning Electron Microscopy. The modifications induced on the surface atomic concentrations were studied by X-ray Photoelectron Spectroscopy. The improvements in terms of the surface morphology after the pre-treatment were also emphasized, as well as the influence of the original stainless steel surface finish.

Electrolytic lesions of the medial septum enhance latent inhibition in a conditioned taste aversion paradigm.

The effects of medial septal lesions on latent inhibition (LI) were assessed in a conditioned taste aversion paradigm. Animals were tested in a LI paradigm 2 weeks after receiving medial septal or sham lesions. The LI paradigm involved a pre-exposure phase in which water-deprived rats were allowed access to either water (non-pre-exposed; NPE) or 5% sucrose (pre-exposed; PE), followed by a conditioning phase in which animals were allowed access to sucrose and subsequently injected with lithium chloride, and a test phase in which animals were allowed access to both sucrose and water. LI was assessed by comparing the %-sucrose consumed in PE and NPE groups on the test day. There was a significantly greater LI effect in the lesion group than in the sham group, suggesting that electrolytic lesions to the medial septum can enhance LI in a CTA paradigm.

The effects of phencyclidine pretreatment on amphetamine-induced behavior and c-Fos expression in the rat.

Previous data demonstrate that a single injection of phencyclidine enhances amphetamine-induced behaviors 24 h later, suggesting that the delayed effects of a single dose of phencyclidine may produce a schizophrenia-like state in animals. These behavioral changes were accompanied by altered patterns of c-Fos induction, suggesting possible neurochemical correlates to the observed behaviors. Because investigations into PCP's ability to model schizophrenia have found that the effects of repeated, or subchronic, PCP administration differ according to the dose and administration paradigm, this study sought to determine whether single and subchronic PCP exposure produce different effects on amphetamine-induced behaviors and c-Fos induction. No differences were observed between these administration paradigms; both single and subchronic PCP exposure enhanced amphetamine-induced c-Fos in the striatum, decreased c-Fos in the prefrontal cortex, and decreased the number of cage-crossings. However, the observation that PCP pretreatment affected c-Fos induction in the same manner observed previously while having an opposite effect on amphetamine-induced behavior suggests that these behavioral and neurochemical effects are dissociated.

The delayed effects of DTG and MK-801 on latent inhibition in a conditioned taste-aversion paradigm.

The delayed effects of phencyclidine (PCP) have been shown to disrupt latent inhibition (LI) in a conditioned taste-aversion paradigm. In an attempt to understand the mechanism of this disruption, the delayed effects of the selective sigma receptor agonist 1,3-Di(2-tolyl)guanidine (DTG) and the selective NMDA receptor antagonist MK-801 on latent inhibition were assessed in the same paradigm. Water-deprived male rats were allowed access to either water (nonpreexposed; NPE) or 5% sucrose (preexposed; PE) for 30 min on 2 consecutive days. On the third day, animals were allowed access to sucrose and subsequently injected with lithium chloride. On the forth day, animals were allowed access to both sucrose and water. LI was assessed by comparing the percent sucrose consumed in PE and NPE groups on the fourth day. DTG (1.0, 5.0, or 10.0 mg/kg), MK-801 (0.5, 1.0, or 2.0 mg/kg), or vehicle was administered IP 20 h before preexposure (days 1 and 2) and conditioning (day 3). In vehicle-treated groups, PE animals consumed a significantly higher percent sucrose on the test day than NPE animals, indicating the presence of LI. DTG (10.0 mg/kg) and MK-801 (2.0 mg/kg) decreased the percent sucrose consumed by animals in the PE group to the level observed in the NPE group, indicating disrupted LI. However, this dose of MK-801 was found to produce a decrease in percent sucrose consumed in PE animals not treated with lithium chloride, indicating that the decrease observed in the LI paradigm could be due to MK-801-induced decrease in taste preference for sucrose rather than a disruption of LI. Lower doses of MK-801 that did not produce a decrease in taste preference for sucrose did not significantly disrupt LI. None of the doses of DTG tested altered taste preference for sucrose. These data suggest a role for sigma receptors in the previously observed PCP-induced disruption of LI. Published by Elsevier Science Inc., 2000

The delayed effects of phencyclidine enhance amphetamine-induced behavior and striatal C-Fos expression in the rat.

The ability for the delayed effects of phencyclidine to model schizophrenia-like symptomatology was investigated by assessing the effects of phencyclidine pretreatment on amphetamine-induced behavior. Corresponding changes in striatal, nucleus accumbens and anterior cingulate cortex c-Fos induction were also assessed in order to test the hypothesis that alterations in the neurochemistry of these regions accompany phencyclidine-induced changes in amphetamine-induced behaviors. Rats were treated with 15.0 mg/kg phencyclidine or vehicle 24 h prior to behavioral testing following vehicle, 0.5, 2.5 or 5.0 mg/kg amphetamine. Phencyclidine pretreatment significantly increased amphetamine-induced locomotion and rearing in response to 0.5 mg/kg amphetamine. Likewise, phencyclidine pretreatment produced an increase in the number of striatal cells expressing c-Fos following treatment with 0.5 mg/kg amphetamine. Phencyclidine pretreatment did not alter c-Fos induction in the nucleus accumbens, but did decrease the basal number of c-Fos-containing cells in the anterior cingulate cortex. While stereotypy rating revealed that phencyclidine pretreatment enhanced the behavioral response to 5.0 mg/kg amphetamine over time, no other alterations in behavior or c-Fos expression in response to the higher doses of amphetamine were induced by phencyclidine pretreatment. These data demonstrate that the delayed effects of a single dose of phencyclidine alter anterior cingulate cortex neurochemistry, and enhance the behavioral and striatal c-Fos response to a low dose of amphetamine. These findings suggest that the delayed effects of a single dose of phencyclidine may produce a reasonable animal model for schizophrenia.

The delayed effects of phencyclidine (PCP) disrupt latent inhibition in a conditioned taste aversion paradigm.

The acute effects of a low dose of phencyclidine (PCP) and the delayed effects of a high dose of PCP on latent inhibition (LI) were assessed in a series of experiments using conditioned taste aversion paradigms. Each paradigm involved a preexposure phase in which water-deprived male rats were allowed access to either water (nonpreexposed; NPE) or 5% sucrose (preexposed; PE), followed by a conditioning phase in which animals were allowed access to sucrose and subsequently injected with the negative reinforcer lithium chloride, and a test phase in which animals were allowed access to both sucrose and water. LI was assessed by comparing the %-sucrose consumed in PE and NPE groups on the test day. The effects of low-dose PCP (2.5 mg/kg) were assessed by comparing LI in animals treated with vehicle or PCP 15 min prior to the onset of the preexposure and conditioning phases. A 4-day paradigm involved 2 days of preexposure followed by a day of conditioning and a test day. This paradigm produced comparable levels of LI in vehicle and PCP-treated animals. A 5-day extinction paradigm involved 2 days of preexposure followed by 2 days of conditioning and a test day. This paradigm abolished LI in vehicle and PCP-treated animals. A 3-day paradigm involved 1 day of preexposure followed by a day of conditioning and a test day. One day of preexposure induced a modified LI effect in both in vehicle and PCP-treated animals. The delayed effects of high dose PCP (8.6 mg/kg) were assessed by comparing LI in animals treated with vehicle or PCP 20 h prior to the onset of the preexposure and conditioning phases in the 4-day paradigm. PCP disrupted latent inhibition in this paradigm. The results are discussed in the context of their relevance to the ability for PCP to model schizophrenic symptomatology.

Behavioral sensitization to amphetamine is not accompanied by a decrease in the number of c-Fos containing cells in the striatum.

The expression of c-Fos-like immunoreactivity (FLI) and chronic Fos-related antigen-like immunoreactivity (FRALI) accompanying behavioral sensitization to amphetamine was assessed in male rat striatum. Animals were treated for four days with amphetamine (A; 5 mg/kg) or vehicle (V) and challenged with A or V on the fifth day. The number of FLI-positive cells in the striatum was enhanced in V-A and A-A groups as compared to control (V-V), while the number of FRALI-positive cells in the striatum was enhanced in the A-V and A-A groups as compared to control. These results suggest that the absence of a decrease in the number of striatal FLI-positive cells accompanying chronic amphetamine treatment is not due to antibody cross-reactivity with chronic FRAs, and that behavioral sensitization to amphetamine is not accompanied by a change in the number of striatal cells expressing c-Fos.

Apomorphine priming alters the response of striatal outflow pathways to D2 agonist stimulation in 6-hydroxydopamine-lesioned rats.

Chronic treatment with dopaminergic agonists is associated with response fluctuations to L-dihydroxyphenylalanine in Parkinson's disease and enhanced motor activity to D1 and D2 dopamine agonists in rats with 6-hydroxydopamine lesions of the nigrostriatal pathway. In dopamine-depleted rodents this phenomenon has been referred to as "priming" or reverse tolerance. The neurochemical changes that underlie "priming" of dopaminergic agonist responses are poorly understood. Some aspects of priming of D1 agonist-mediated rotation in the 6-hydroxydopamine-lesioned rat have been characterized, but priming of D2-agonist-dependent motor responses has been less thoroughly studied. In this study, examination of rotational behaviour and induction of Fos-like immunoreactivity were used to investigate changes in the striatal outflow systems in response to treatment with the D2 agonist quinpirole in 6-hydroxydopamine-lesioned rats that had been primed with apomorphine. Administration of apomorphine (0.5 mg/kg; three injections at three to six day intervals) permitted an otherwise inactive dose of quinpirole (0.25 mg/kg) to produce robust contralateral rotation and to induce the expression of Fos in striatal neurons belonging to the striato-nigro-entopeduncular ("direct") pathway. The increase in contralateral rotation and ipsilateral striatal Fos expression following administration of quinpirole to apomorphine-primed rats was mediated by a D2-like receptor and did not appear to be due to a change in sensitivity of D2 receptors. Apomorphine priming also enhanced the ability of quinpirole to induce Fos expression in the globus pallidus, a target of the striatopallidal ("indirect") pathway. Western blot analysis confirmed that treatment with quinpirole induced the expression of c-Fos protein with no change in the expression of 35-37,000 mol. wt Fos-related antigens in apomorphine-primed rats treated with water or quinpirole. Induction of Fos expression in the striatum generally results from blockade of D2 receptors and the striato-nigro-entopeduncular pathway preferentially expresses D1 receptors. Thus, the quinpirole-dependent induction of striatal Fos in apomorphine-primed 6-hydroxydopamine-lesioned rats represents a qualitative alteration in striatal outflow. These studies demonstrate that pretreatment of 6-hydroxydopamine-lesioned rats with apomorphine increases the activity of the "direct" and "indirect" striatal outflow pathways in response to D2 receptor stimulation. These changes have the net result of enhancing thalamocortical activity and likely underlie the enhanced contralateral rotation produced by quinpirole in apomorphine-primed rats. Changes in striatal outflow, particularly in the striato-nigro-entopeduncular pathway, may contribute to alterations in D2-dependent motor responses observed after chronic dopaminergic stimulation in the dopamine-depleted striatum.

Enhanced CREB phosphorylation and changes in c-Fos and FRA expression in striatum accompany amphetamine sensitization.

Expression in striatum of c-Fos, a 35 kDa Fos-related antigen (FRA) and the phosphorylated form of cyclic AMP response element binding protein (phosphoCREB) was assessed using Western blots in rats that developed behavioral sensitization following repeated amphetamine administration. Treatment with d-amphetamine (5 mg/kg) for 5 consecutive days produced behavioral sensitization. Similar to previous observations using chronic cocaine administration, amphetamine sensitized animals had decreased c-Fos and increased FRA proteins in striatum. Supershift analysis with antisera to c-Fos and FRA proteins demonstrated that 4-Fos and the 35 kDa FRA are components of the striatal AP-1 binding complex from sensitized rats. Thus, amphetamine sensitization is accompanied by alterations in the composition of the AP-1 DNA binding complex. An increased amount of phosphoCREB protein was also present in the striatum of amphetamine sensitized rats. These results suggest that alterations in Fos, FRA and CREB transcription factors are common neuronal responses to chronic psychostimulant administration and may contribute to regulation of genes important to the neuroplastic changes underlying psychostimulant sensitization.

GABAA receptor binding in the aging rat inferior colliculus.

The inhibitory neurotransmitter GABA has been shown to be critically involved in shaping neuronal responses to simple and complex acoustic stimuli in the inferior colliculus. Studies in the rat and human inferior colliculus have suggested significant changes in functions related to GABA neurotransmission occur in the aged. These changes include significant decreases in GABA content, GABA release, GABA neurons, glutamate decarboxylase enzymatic activity, and GABAB receptor binding. Such changes within the inferior colliculus may affect the ability of elderly listeners to process complex acoustic signals, particularly in the presence of background noise. The present study was designed to examine the regional distribution and effects of aging on GABAA receptor binding sites in the Fischer 344 rat inferior colliculus using in vitro quantitative receptor autoradiography. [3H]GABA binding to GABAA receptors was significantly reduced in the inferior colliculus of young adult (3 months) and aged (18-26 months) rats when compared to 2-month animals. However, no significant changes were observed after 3 months of age. Single concentrations of tritiated GABAA receptor ligands (muscimol, t-butylbicycloorthobenzoate, and flunitrazepam) revealed no significant age-related changes in receptor binding in the inferior colliculus between 3 and 26 months of age. To characterize further the pharmacology of the GABAA receptor in the inferior colliculus, GABA modulation of the picrotoxin binding site was examined using [3H]t-butylbicycloorthobenzoate. When increasing concentrations of GABA were added to the incubation buffer, a significant decrease in binding was observed in the inferior colliculus of rats in each age group. In aged rats, the dose-response curve was shifted to the left, indicating an increase in the potency of GABA to inhibit [3H]t-butylbicycloorthobenzoate binding. Although no changes in GABAA receptor binding were detected in the inferior colliculus after 3 months of age, a significant alteration in interaction between the GABA and picrotoxin binding sites was observed in the inferior colliculus of aged rats when compared to 3-month-old young adults. This difference appears to reflect an increased sensitivity of the receptor to GABA modulation in aged rats and, thus, may serve as a compensatory mechanism to enhance GABAA receptor function in response to a presynaptic loss of inhibition.