Repeated moderate-dose ethanol bouts impair cognitive function in Wistar rats.

The effects of repeated, intermittent administration of a moderate dose of ethanol (3.4 g/kg/day × 6 days, intragastrically via gavages) on cognitive function were examined in male Wistar rats. No significant differences in weight gain between the ethanol- and water-treated rats were found. Analysis of physical dependence revealed no signs of spontaneous withdrawal, whereas withdrawal signs exacerbated by Ro15-4513, an inverse benzodiazepine agonist, were apparent 5 hours but not 24 hours after the cessation of ethanol treatment. Spatial learning and memory, as assessed in the Barnes maze, were impaired 3-6 days following the treatment but recovered by the 11th-14th days. Reversal learning, however, was impaired throughout the 2-week observation period. Thus, bouts of moderate-dose ethanol administration transiently impair spatial learning and memory, and promote cognitive inflexibility. The employed ethanol exposure paradigm may provide a model of human cognitive deficits associated with alcohol binge drinking.

Enhanced cerebral expression of MCT1 and MCT2 in a rat ischemia model occurs in activated microglial cells.

Monocarboxylate transporters (MCTs) are essential for the use of lactate, an energy substrate known to be overproduced in brain during an ischemic episode. The expression of MCT1 and MCT2 was investigated at 48 h of reperfusion from focal ischemia induced by unilateral extradural compression in Wistar rats. Increased MCT1 mRNA expression was detected in the injured cortex and hippocampus of compressed animals compared to sham controls. In the contralateral, uncompressed hemisphere, increases in MCT1 mRNA level in the cortex and MCT2 mRNA level in the hippocampus were noted. Interestingly, strong MCT1 and MCT2 protein expression was found in peri-lesional macrophages/microglia and in an isolectin B4+/S100beta+ cell population in the corpus callosum. In vitro, MCT1 and MCT2 protein expression was observed in the N11 microglial cell line, whereas an enhancement of MCT1 expression by tumor necrosis factor-alpha (TNF-alpha) was shown in these cells. Modulation of MCT expression in microglia suggests that these transporters may help sustain microglial functions during recovery from focal brain ischemia. Overall, our study indicates that changes in MCT expression around and also away from the ischemic area, both at the mRNA and protein levels, are a part of the metabolic adaptations taking place in the brain after ischemia.

Secondary brain injuries in thalamus and hippocampus after focal ischemia caused by mild, transient extradural compression of the somatosensori cortex in the rat.

The development and distribution of secondary brain lesions, subsequent to ischemic stroke, are of considerable clinical interest but so far only a limited number of studies have investigated the distribution and development of these secondary lesions in detail. In this study, we used an animal model of focal ischemia caused by extradural compression of the sensorimotor cortex. This paradigm of focal ischemia was shown to produce a consistent pattern of secondary lesions located distally from the primary lesion. Functionally the primary brain lesion produced a transient neurological deficit, which was evaluated by daily beam walking tests. Morphological changes were assessed in parallel after the ischemic event using Fluoro-Jade (FJ) staining as a marker of neuronal cell death. Secondary brain lesions were observed in the thalamus as well as in the hippocampus. The first sign of the slowly developing secondary brain lesions was present on day 3 with subsequent lesions being identified until day 16 after the primary ischemia. In addition to the identification of neuronal cell death by the FJ assays, immunostaining for parvalbumin (PA), a marker of GABAergic interneurons, revealed a loss of PA-staining in the pyramidal layer of CA1 on day 3, thus showing a similar time pattern for loss of PA-staining as for the loss of FJ stained cells. Based upon our present results, we suggest that the current animal model of focal ischemia represents a valuable tool for studies concerning the development of secondary remote brain lesions and their association to impaired motor and cognitive functions.

Effects of subunit selective nACh receptors on operant ethanol self-administration and relapse-like ethanol-drinking behavior.

RATIONALE AND OBJECTIVES: The sensitivity to ethanol central effects is partially determined by the subunit composition of brain nicotinic acetylcholine receptors (nAChRs). Thus, the effects of intraventral tegmental area (VTA) administration of the nicotinic subunit-specific antagonist, alpha-conotoxin MII (alphaCtxMII, alpha(3)beta(2)*, beta(3)*, alpha(6)*), were compared to those of systemic mecamylamine (MEC, an allosteric negative modulator of the nAChR), dihydro-beta-erythroidine (DHbetaE, alpha(4)beta(2)*), and methyllycaconitine (MLA, alpha(7)*) to elucidate involvement of different subunits of nAChRs in operant ethanol self-administration and relapse-like activation of ethanol consumption after ethanol deprivation in rats. METHODS: The effects of drugs were studied in rats trained for operant oral self-administration of ethanol (FR = 1). For ethanol deprivation, trained animals were subjected to a period of alcohol deprivation for 10 days. alphaCtxMII was given directly into the VTA through implanted permanent intracranial cannulae, whereas MEC, DHbetaE, and MLA were administered systemically. RESULTS: alphaCtxMII reduced operant ethanol self-administration and blocked the deprivation-induced relapse-like ethanol consumption. MEC reduced operant ethanol self-administration and inhibited the deprivation-induced increase in alcohol consumption. DHbetaE did not alter ethanol self-administration in the lower-dose range but inhibited ethanol intake at a higher dose (4 mg/kg), although this effect might have been nonspecific. MLA failed to block self-administration of ethanol and relapse-like drinking after deprivation. CONCLUSIONS: Our results indicate that nAChRs are involved in the modulation of operant alcohol self-administration and relapse-like alcohol drinking behavior in rats. Our observations support the working hypothesis that systemically active selective ligands for nAChR alpha(3)beta(2)*, beta(3), and/or alpha(6)* receptor subunits might be of therapeutic value for the treatment of alcoholism.

Memantine enhances the inhibitory effects of naltrexone on ethanol consumption.

Effects of the opioid receptor antagonist naltrexone (0.1; 0.3; 1.0 mg/kg i.p.) on operant ethanol self-administration alone and in combination with the non-competitive NMDA antagonist memantine (0.5 and 1 mg/kg, i.p.) were studied in rats. Acute administration of naltrexone (0.1; 0.3; 1.0 mg/kg i.p.) inhibited ethanol self-administration in a dose-dependent manner. Memantine (1.0 mg/kg) significantly enhanced the effects of naltrexone at 0.1 mg/kg, failing per se to inhibit ethanol consumption. Thus, low, sub-effective dose of memantine in combination with low doses of naltrexone blocked the reinforcing properties of ethanol in rats. It is suggested that the combination of sub-effective doses of memantine and naltrexone may have therapeutic value in the treatment of alcoholism particularly in a subgroup of alcoholic patients who have high sensitivity to the adverse side effects of naltrexone.

The role of hypothalamic peptide gene expression in alcohol self-administration behavior.

Self-administration of ethanol and food share many common features and Richter hypothesized that an increase in ethanol consumption would decrease feeding to balance the excess calories contained in the ethanol. Previously, we have shown that individual alcohol consumption correlates with neurotransmitter gene expression, especially in the prefrontal cortex. To test the hypothesis of Richter, we measured hypothalamic gene expression of receptors or neuropeptides of known relevance for the regulation of food intake using qPCR and correlated this to individual ethanol consumption in Wistar rats. For validation, gene expression was first correlated with body weight. We found a correlation of dynorphin, somatostatin, melanocortin-4 receptor and serotonin 5-HT(2C) with body weight and trends to correlation for CART, thus confirming the established role of the hypothalamus in the regulation of weight. For ethanol consumption, correlations were found for CRH receptors 1 and 2 and vasopressin while strong trends were observed for galanin receptor 1, orexin receptor 1, MCH and adrenoceptor alpha(1B). Therefore, alcohol consumption does seem to involve several hypothalamic systems which also mediate feeding responses and suggests that the hypothalamus, together with the prefrontal cortex, may determine the 'stopping point' of an individual.

Diabetic type II Goto-Kakizaki rats show progressively decreasing exploratory activity and learning impairments in fixed and progressive ratios of a lever-press task.

Learning and memory impairments associated with diabetes have been reproduced in rodent models of diabetes type I, but few studies have been performed in spontaneously type II diabetic rodents. The study of type II diabetic rats such as the Goto-Kakizaki (GK) rat is of advantage when characterizing the development of cognitive impairments specifically caused by the progression of the disease and not by its treatment. We thus hypothesized that GK rats might display learning impairments when compared to non-diabetic Wistar rats. In the present study, we employed a lever-press task, a behavioural paradigm which allows the study of response-reinforcement learning, discrimination of a rewarding lever (using a two-choice positional discrimination task), and the ability to increase operant behaviour when requirements for reward increase (using a progressive ratio [PR]). In parallel, locomotor activity was compared between strains to assess exploratory activity and behavioural habituation to a novel environment. Diabetic GK rats made significantly less lever-presses with increasing fixed ratios and, throughout the sessions, a trend for increased selection errors was observed in these animals. In addition, a significant reduction in the maximum number of lever-presses made by GK rats was observed during the PR sessions. Locomotor activity of GK rats was higher on the first day of exploration but significantly decreased with familiarization to the environment. The present results suggest that the diabetic-like symptomatology in GK rats led to a reduction of exploratory activity and of lever-pressing during fixed and progressive ratio schedules, likely caused by learning impairments.

Reduced HO-1 protein expression is associated with more severe neurodegeneration after transient ischemia induced by cortical compression in diabetic Goto-Kakizaki rats.

Pronounced hyperglycemia provoked by extradural compression (EC) of the sensorimotor cortex was recently described in the non-insulin dependent Goto-Kakizaki (GK) diabetic rat. Compared with control Wistar rats, GK rats exhibited more extensive brain damage after cortical ischemia at 48 h of reperfusion (Moreira et al, 2007). We hypothesized that the enhanced brain injury in GK rats could be caused by differential regulation of the heme degrading enzyme heme oxygenase (HO)-1, known to interact with the expression of other target genes implicated in antioxidant defense, inflammation and neurodegeneration, such as superoxide dismutase (SOD)-1, -2, inducible nitric oxide synthase (iNOS), and tumor necrosis factor-alpha (TNFalpha). At 48 h after ischemia, relative mRNA expression of such target genes was compared between ipsilateral (compressed) and contralateral (uncompressed) hemispheres of GK rats, along with baseline comparison of sham, uncompressed GK and Wistar rats. Immunohistochemistry was performed to detect cellular and regional localization of HO-1 at this time point. Baseline expression of HO-1, iNOS, and TNFalpha mRNA was increased in the cortex of sham GK rats. GK rats showed pronounced hyperglycemia during EC and transient attenuation of regional cerebral blood flow recovery. At 48 h after reperfusion, HO-1 mRNA expression was 7- to 8-fold higher in the ischemic cortex of both strains, being the most upregulated gene under study. Heme oxygenase-1 protein expression was significantly reduced in diabetic rats and was found in perilesional astrocytes and rare microglial cells, in both strains. The reduced HO-1 protein expression in GK rats at 48 h after reperfusion combined with more extensive neurodegeneration induced by EC, provides further in vivo evidence for a neuroprotective role of HO after brain ischemia.

Delayed access to alcohol accelerates self-administration of alcohol on a progressive ratio schedule.

In a previous report, we found that a 5-min. delay in alcohol access increases ethanol intake in rats trained to self-administer 5% ethanol. To assess the effects of this delay on the motivation to self-administer ethanol, Wistar rats were trained on a progressive ratio schedule of reinforcement and presented with the 5-min. delay. There was no change in break point (6 presses/delivery), active (125 presses/30 min.) or inactive (10 presses/30 min.) lever presses after the 5-min. delay compared to baseline. However, response cessation occurred 10 min. earlier in this delay session compared to baseline indicating that consumption was accelerated by delayed access to alcohol.

To press or not to press? Differential receptor expression and response to novelty in rats learning an operant response for reward.

Learning to perform instrumental tasks is an ability of all animals. In a population of rats, not all individuals will acquire an operant response for reward. We hypothesized that there could be a genetic explanation for differences between High Consumers (those that acquired the lever press response) and Low Consumers (lever press response is low). Additionally, we proposed that this genetic difference could produce measurable changes in response to novelty. Wistar rats were trained to lever press for a 0.2% saccharin reward and on the 10th day they were placed in a novel open field for 30 min to record locomotor activity. The prefrontal cortex and hippocampus were dissected and qPCR was used to measure mRNA expression. A significant difference (p=.048; 2-way ANOVA) in gene expression was observed between Low and High Consumers. A principal component analysis (PCA), to cluster which genes represent this difference, identified 4 genes; 5-HT2A and mGlu1 in the hippocampus and AMPA GluR1 and adrenergic alpha2A in the prefrontal cortex. Response to a novel open field also differed since Low Consumers displayed a higher Total Distance in comparison to High Consumers. Additionally, Low Consumers could be subdivided into Low-Lever (with lever press response only when water deprived) and Low-Non-Lever (lever press response is low throughout training). PCA with this subdivision identified an additional nine genes differing within the divisions; NMDA NR2B and GABAAalpha3 in the prefrontal cortex and adrenergic alpha2B and alpha2A, AMPA GluR1, GluR2 and GluR3, 5-HT1B and GABAAalpha5 in the hippocampus.

The nociceptin/orphanin FQ receptor agonist Ro 64-6198 reduces alcohol self-administration and prevents relapse-like alcohol drinking.

Effects of the opioid receptor like-1 (ORL-1) receptor agonist Ro 64-6198 (0.1, 0.3, and 1.0 mg/kg intraperitoneally (i.p.)) on operant ethanol self-administration and activation of self-administration by ethanol deprivation were studied in male Wistar rats. Acute administration of Ro 64-6198 caused a dose-dependent reduction of ethanol self-administration. In comparison, the opioid antagonist naltrexone (0.1, 0.3, and 1.0 mg/kg i.p.) inhibited ethanol self-administration at all doses tested. Ethanol deprivation for 10 days significantly increased ethanol self-administration during the first 2 days after deprivation. Daily pretreatment with Ro 64-6198 (0.3 mg/kg) or naltrexone (0.3 mg/kg) during the last 3 days of ethanol deprivation abolished the deprivation-induced increase in ethanol intake. Thus, stimulation of the ORL-1 receptors by Ro 64-6198 reduced the acute reinforcing effects of ethanol and prevented relapse-like behavior in the ethanol-deprivation model in a similar manner as a blockade of opioid receptors by naltrexone. Ro 64-6198 at 0.1 and 0.3 mg/kg doses did not alter self-administration of 0.2% saccharin solution, indicating an apparent selectivity of this compound in modification of ethanol reward. These findings add further support to the idea that Ro 64-6198 and potentially other synthetic ORL-1 receptor agonists are as effective as naltrexone in blocking the actions of ethanol important for its addictive potential in animal experiments, and therefore may have therapeutic value in the treatment of alcoholism.

Identification of neurotransmitter receptor genes involved in alcohol self-administration in the rat prefrontal cortex, hippocampus and amygdala.

About half of the risk to develop alcoholism is related to genetic background and it is well known that alcohol consumption is highly individualized. In this study, we investigated how individual alcohol consumption behaviour in Wistar rats correlated with mRNA expression of 20 genes in the prefrontal cortex, hippocampus and amygdala. We found that the long-term alcohol consumption of an individual could be estimated by the mean of its consumption on Day 2 and 3. This short exposure minimized changes in gene expression induced by alcohol itself. We found a positive correlation in the prefrontal cortex of GABA(A) alpha5 (r=0.96), GABA(B1) (r=0.96), AMPA GluR1 (r=0.93), 5-HT(3A) (r=0.93) and the alpha adrenoceptors (alpha(1A)r=1.00, alpha(1B)r=0.93, alpha(2A)r=0.93) with consumption. In the hippocampus, we found negative correlations with the NMDA NR2A subunit (r=-0.86), the alpha(1A) adrenoceptor (r=-0.89) and the glucocorticoid receptor (r=-0.86). Finally, in the amygdala there was a negative correlation to NMDA NR2A (r= -0.79) and a positive correlation with serotonin 5-HT(2C) (r=0.79). In conclusion, we have used qPCR to identify specific genes in the brain that correlated to alcohol self-administration of an individual animal. This study suggests that alcohol consumption in the early stages of acquisition depends on the genetic background of the individual and that the prefrontal cortex is particularly important in this behaviour.

Repeated maternal separation of male Wistar rats alters glutamate receptor expression in the hippocampus but not the prefrontal cortex.

Stress early in life puts the individual at a greater risk for developing mental disorders in adulthood. The animal model of maternal separation involves daily removal of pups from their mother over the early postnatal period and leads to several behavioral deficits in adults. Since this period corresponds to a time of extensive developmental changes in the glutamatergic system, glutamate receptor mRNA expression was studied in the hippocampus and prefrontal cortex. Male Wistar rats were either separated from their mother for 15 min (MS15 or 'handling') or 360 min (MS360) once a day from pnd 1-21 and glutamate receptor expression levels were measured at 25 weeks of age using real-time RT-PCR analysis. A third group of animal facility reared (AFR) rats was included as a control for the handling group. In the hippocampus, mRNA expression of NMDA NR2B and AMPA GluR1 and GluR2 receptors was significantly lower in MS360 rats relative to MS15. In addition, expression of the glutamate transporter GLAST was increased in MS360 relative to MS15. No differences were observed for AFR rats relative to MS15, which indicates that the hippocampal effects were not a result of handling or maternal care. For the prefrontal cortex, no difference in mRNA expression was observed for NMDA NR2A and NR2B or AMPA GluR1 and GluR2. These findings suggest that prolonged maternal separation produces neuroadaptive changes in the hippocampus that may, at least partially, account for the behavioral deficits previously observed in this animal model.

Impaired long-term habituation is dissociated from increased locomotor activity after sensorimotor cortex compression.

Behavioural habituation to a novel environment is a simple form of learning in rodents. We studied the habituation and locomotor activity (LMA) of Wistar rats subjected to unilateral, transient (30min) extradural compression (EC) of the right sensorimotor cortex. One group of rats was tested every 24h during the first 5 days (D1-D5) post-EC. Two other groups were tested for the first time in the LMA boxes on D3 and D6 post-EC and their performance was compared with the group tested on D1 (activity in a novel environment). Total and center locomotion, vertical activity and time spent in the center of the LMA box were reduced on D1 post-EC and normalized by D2. The EC-induced motor paresis was undetectable on the rotarod by D2 and on the beam-walking by D3. Total locomotion, vertical activity and time spent in the center of EC-rats significantly increased from D1 to D3. EC caused neurodegeneration in the cortex, caudate putamen and thalamus as detected by Fluoro-Jade staining. The size of the cortical damage decreased from D2 to D5 in the medial and caudal regions of the compressed hemisphere, in accordance with recovery of motor function. LMA provided additional information in the follow-up of recovery from brain injury and habituation to the environment. Thus, long-term, inter-session habituation was impaired from D1 to D3 but dissociated from increased LMA intra-session on D3, when the motor deficits provoked by EC were already undetectable in the rotarod and beam-walking tests.

Extradural compression of the sensorimotor cortex delays the acquisition but not the recalling of a lever-pressing task in Wistar rats.

The learning and recalling of a lever-press task (LPT) after brief unilateral extradural compression (EC) of the right sensorimotor cortex was studied in Wistar rats. All rats, regardless of the time-point for EC, were trained to lever press for food from D(day)1 to D6. On D8, the position of the active lever was changed to the right side of the operant box and performance was tested until D14. Total and active lever presses, as well as % errors were used to analyse the performance. Rats submitted to EC 24 h before initiating the LPT schedule (naïve-compressed group) showed delayed task acquisition and impaired performance until D10. No significant impairments were detected by D3 on a beam-walking test, excluding paresis as the cause to the delay. Rats submitted to EC after they learned the LPT (trained-compressed group) showed only mildly impaired post-compression performance with no effects on the recalling of the task. Using a progressive ratio LPT, the maximum number of presses to obtain a food-pellet (breaking point) was significantly reduced 24h after EC suggesting reduced motivation for the task early after brain injury. The delayed acquisition of the LPT in naïve-compressed rats was accompanied by consistent cortical, striatal and thalamic degeneration detected by Fluoro-Jade and anti-glial fibrillary acidic protein (GFAP) staining, whereas the improvement in the performance of this group was accompanied by a reduction of the cortical damage on D10. Recall of the LPT in trained-compressed rats was not altered by EC, suggesting the contribution of compensatory mechanisms.

Behavioural sensitization to nicotine precedes the onset of nicotine-conditioned locomotor stimulation.

Context-dependent behavioural sensitization to nicotine develops faster and is more robust than context-independent sensitization. However, some findings suggest that behavioural sensitization develops irrespective of context. In this study an attempt was made to dissociate the development of context-dependent nicotine sensitization from the onset of nicotine-conditioned locomotor stimulation. Seven days of daily nicotine administration (0.6 mg/kg, s.c.) paired with exposure to locomotor activity boxes produced stable and consistent behavioural sensitization, at which time no nicotine-induced conditioned locomotor stimulation could be demonstrated. However, after an additional two days of nicotine treatment, i.e. on day 9, nicotine-conditioned behavioural stimulation was observed. Our findings suggest that behavioural sensitization to nicotine appears to reach a plateau before induction of nicotine-conditioned locomotor stimulation.

Fluoro-Jade and TUNEL staining as useful tools to identify ischemic brain damage following moderate extradural compression of sensorimotor cortex.

Cerebral ischemia was produced by moderate compression for 30 min of a specific brain area in the sensorimotor cortex of Sprague-Dawley rats. On day 1, that is 24 h after the transient sensorimotor compression, ischemia-exposed animals displayed a marked focal neurological deficit documented as impaired beam walking performance. This functional disturbance was mainly due to contralateral fore- and hind-limb paresis. As assessed by daily beam walking tests it was shown that there was a spontaneous recovery of motor functions over a period of five to seven days after the ischemic event. Using histopathological analysis (Nissl staining) we have previously reported that the present experimental paradigm does not produce pannecrosis (tissue cavitation) despite the highly reproducible focal neurological deficit. We now show how staining with fluorescent markers for neuronal death, that is Fluoro-Jade and TUNEL, respectively, identifies regional patterns of selective neuronal death. These observations add further support to the working hypothesis that the brain damage caused by cortical compression-induced ischemia consists of scattered, degenerating neurons in specific brain regions. Postsurgical administration of the AMPA receptor specific antagonist, LY326325 (30 mg/kg; i.p., 70 min after compression), not only improved beam walking performance on day 1 to 3, respectively but also significantly reduced the number of Fluoro-Jade stained neurons on day 5. These results suggest that enhanced AMPA/glutamate receptor activity is at least partially responsible for the ischemia-produced brain damage detected by the fluorescent marker Fluoro-Jade.

The NR2B-selective N-methyl-D-aspartate receptor antagonist Ro 25-6981 [(+/-)-(R*,S*)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperidine propanol] potentiates the effect of nicotine on locomotor activity and dopamine release in the nucleus accumbens.

It has been proposed that nicotine-stimulated locomotor activity (LMA) and nicotine-induced dopamine (DA) release in the mesocorticolimbic DA system is partly regulated by glutamate receptors, particularly N-methyl-D-aspartate (NMDA) receptors. The functional characteristics of NMDA receptors depend on their subunit composition (NR1 in combination with NR2A-D). In the present study, we investigated the effect of the NR2B-selective NMDA receptor antagonist Ro 25-6981 [(+/-)-(R*,S*)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperidine propanol] on nicotine-stimulated LMA and nicotine-induced DA release in the nucleus accumbens (NAcc) in rats. Ro 25-6981 (3 and 10 mg/kg i.p.) given 10 min prior to a high dose (0.6 mg/kg s.c.) or a subthreshold dose (0.1 mg/kg s.c.) of nicotine potentiated nicotine-stimulated LMA with no effect when administered alone. Similarly, administration of a low dose (0.05 mg/kg i.p.) of the noncompetitive NMDA receptor antagonist MK-801 (dizocilpine maleate) had no effect on LMA by itself but potentiated nicotine-induced (0.1 mg/kg) LMA. However, pretreatment with the competitive NMDA receptor antagonist CGP39551 [(E)-(+/-)-2-amino-4-methyl-5-phosphono-3-pentenoic acid ethyl ester] (10 mg/kg i.p.) did not potentiate the LMA effect of 0.1 mg/kg nicotine as seen with Ro 25-6981. In vivo microdialysis revealed a significant increase of DA release in the NAcc in response to nicotine (0.1 mg/kg s.c.). In analogy to our LMA data, Ro 25-6981 (10 mg/kg i.p.) significantly potentiated the nicotine-induced DA release, although it had no effect on DA release when given alone. The data suggest that, compared with other subunits of the NMDA receptor, the NR2B subunit might play a different role in the reinforcing effects of nicotine.

Nicotine-induced dopamine release in the nucleus accumbens is inhibited by the novel AMPA antagonist ZK200775 and the NMDA antagonist CGP39551.

RATIONALE: Accumulated data suggest that N-methyl-D-aspartate (NMDA) receptors are involved in the reinforcing properties of nicotine. However, less is known about the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA) receptors in this context. OBJECTIVES: To study the effect of the novel systemically administered AMPA receptor antagonist ZK200775 ([1,2,3,4-tetrahydro-7-morpholinyl-2,3-dioxo-6-(fluoromethyl) quinoxalin-1-yl] methylphosphonate) on nicotine-induced dopamine (DA) release in the nucleus accumbens (NAcc) and nicotine-stimulated locomotor activity (LMA) and particularly the relative role of NMDA and AMPA receptors in nicotine-stimulated DA release and LMA. METHODS: Male Wistar rats were administered ZK200775, CGP39551 or NBQX 30 min prior to nicotine and DA release and LMA was measured using in vivo microdialysis or photocell equipped activity boxes. Glutamate-produced neurotoxicity in cultured brain cells and binding assays were performed to determine the glutamate receptor subtype selectivity and affinity to nicotine receptors of ZK200775, respectively. RESULTS: ZK200775 (3.0 but not 1.5 or 6.0 mg/kg) significantly decreased the nicotine-induced (0.6 mg/kg) DA release in the NAcc and nicotine-stimulated LMA. ZK200775 (1.5, 3.0, 6.0 mg/kg) alone influenced neither DA release nor LMA. ZK200775 showed 34-fold selectivity for AMPA receptors compared to NMDA receptors and no affinity to nicotine receptors. The NMDA receptor antagonist CGP39551 (10 mg/kg) significantly decreased both the nicotine-induced DA release and nicotine-stimulated LMA whereas the AMPA receptor antagonist NBQX (10 mg/kg) had no effect. Notably, CGP39551 and ZK200775 (3.0 mg/kg) displayed a different pattern in inhibition of nicotine-induced DA release. CONCLUSIONS: Both NMDA- and AMPA receptors are involved in nicotine's dependence-producing properties, although in a spatiotemporally differential manner.

The NMDA NR2B subunit-selective receptor antagonist, CP-101,606, enhances the functional recovery the NMDA NR2B subunit-selective receptor and reduces brain damage after cortical compression-induced brain ischemia.

Using a novel in vivo model for cerebral ischemia produced by short-lasting compression of a well-defined brain area of sensorimotor cortex we studied neuroprotective effects of the NMDA NR2B subunit selective antagonist, CP-101,606, in Sprague-Dawley rats. Cortical compression for 30 min produced a consistent and highly reproducible functional impairment, that is paresis of contralateral hind and fore limbs. The neurological deficit was accompanied by marked brain damage in cerebral cortex, hippocampus and thalamus as identified by Fluoro-Jade, a marker of general neuronal cell death. Using a daily performed beam walking test it was shown that untreated animals recovered from their functional impairment within 5-7 days following surgery. Intravenous administration of increasing doses (1, 5, 10, 20 mg/kg) of the NMDA NR2B subunit receptor specific antagonist, CP-101,606, dose-dependently improved the rate of functional recovery and protected against the ischemic brain damage in cerebral cortex, hippocampus, and thalamus as identified 2 days after the ischemic insult. Based upon these results, we conclude that NMDA NR2B receptor subunits represent potential targets to reduce not only the functional deficits, but also neuronal death in cortex and several midbrain regions produced by moderate, transient, cerebral ischemia.