Elevated BDNF mRNA expression in the medial prefrontal cortex after d-amphetamine reinstated conditioned place preference in rats

Physical Exercise Promotes Beneficial Changes on Neurotrophic Factors in Mesolimbic Brain Areas After AMPH Relapse: Involvement of the Endogenous Opioid System

Addiction is a serious public health problem, and the current pharmacotherapy is unable to prevent drug use reinstatement. Studies have focused on physical exercise as a promising coadjuvant treatment. Our research group recently showed beneficial neuroadaptations in the dopaminergic system related to amphetamine-relapse prevention involving physical exercise-induced endogenous opioid system activation (EXE-OS activation). In this context, additional mechanisms were explored to understand the exercise benefits on drug addiction. Male rats previously exposed to amphetamine (AMPH, 4.0 mg/kg) for 8 days were submitted to physical exercise for 5 weeks. EXE-OS activation was blocked by naloxone administration (0.3 mg/kg) 5 min before each physical exercise session. After the exercise protocol, the rats were re-exposed to AMPH for 3 days, and in sequence, euthanasia was performed and the VTA and NAc were dissected. In the VTA, our findings showed increased immunocontent of proBDNF, BDNF, and GDNF and decreased levels of AMPH-induced TrkB; therefore, EXE-OS activation increased all these markers and naloxone administration prevented this exercise-induced effect. In the NAc, the same molecular markers were also increased by AMPH and decreased by EXE-OS activation. In this study, we propose a close relation between EXE-OS activation beneficial influence and a consequent neuroadaptation on neurotrophins and dopaminergic system levels in the mesolimbic brain area, preventing the observed AMPH-relapse behavior. Our outcomes bring additional knowledge concerning addiction neurobiology understanding and show that EXE-OS activation may be a potential adjuvant tool in drug addiction therapy.

The path from trigeminal asymmetry to cognitive impairment: a behavioral and molecular study

Trigeminal input exerts acute and chronic effects on the brain, modulating cognitive functions. Here, new data from humans and animals suggest that these effects are caused by trigeminal influences on the Locus Coeruleus (LC). In humans subjects clenching with masseter asymmetric activity, occlusal correction improved cognition, alongside with reductions in pupil size and anisocoria, proxies of LC activity and asymmetry, respectively. Notably, reductions in pupil size at rest on the hypertonic side predicted cognitive improvements. In adult rats, a distal unilateral section of the trigeminal mandibular branch reduced, on the contralateral side, the expression of c-Fos (brainstem) and BDNF (brainstem, hippocampus, frontal cortex). This counterintuitive finding can be explained by the following model: teeth contact perception loss on the lesioned side results in an increased occlusal effort, which enhances afferent inputs from muscle spindles and posterior periodontal receptors, spared by the distal lesion. Such effort leads to a reduced engagement of the intact side, with a corresponding reduction in the afferent inputs to the LC and in c-Fos and BDNF gene expression. In conclusion, acute effects of malocclusion on performance seem mediated by the LC, which could also contribute to the chronic trophic dysfunction induced by loss of trigeminal input.

Microinjection of the BDNF receptor antagonist ANA-12 into the nucleus accumbens and medial-prefrontal cortex attenuates morphine-induced reward memory, and alterations of BDNF levels and apoptotic cells in rats

This study was designed to examine the effects of intra- nucleus accumbens (NAc) of BDNF receptor antagonist ANA-12 on the acquisition and expression and intra- medial-prefrontal cortex (mPFC) of ANA-12 on the extinction and reinstatement of morphine-induced conditioned place preference (CPP) and also BDNF levels and apoptotic neurons in the NAc and mPFC of rats. In this study, adult male Wistar rats (200-250 g) were used. Two separate cannulas were inserted bilaterally into the NAc and/or mPFC. ANA-12 (3 μg/0.5 μl/side) was injected into the NAc and/or mPFC to evaluate the rewarding effects of morphine using a CPP paradigm. Then, the levels of BDNF and apoptotic in the NAc and mPFC were assessed at the end of each treatment phase using ELISA and TUNEL methods, respectively. All of vehicle-treated rats following morphine CPP showed the increase of BDNF levels and apoptotic neurons in the NAc and mPFC. ANA-12 significantly attenuated the acquisition and expression of morphine-induced CPP, BDNF levels and apoptotic neurons in the NAc during the acquisition, but not the expression phase. Also, ANA-12 significantly facilitated the extinction, but no effect on reinstatement of morphine CPP, and decreased BDNF levels and apoptotic neurons in the mPFC during the extinction, but not the reinstatement. We conclude that blocking TrkB with ANA-12 showed therapeutic effects on morphine-associated reward memory and neuronal death in the NAc and mPFC induced by morphine CPP. Thus, the BDNF-TrkB signaling may be important in the acquisition, expression, extinction, but not the reinstatement of morphine CPP.

High-glucose/high-cholesterol diet in zebrafish evokes diabetic and affective pathogenesis: The role of peripheral and central inflammation, microglia and apoptosis

Neuroinflammation and metabolic deficits contribute to the etiology of human affective disorders, such as anxiety and depression. The zebrafish (Danio rerio) has recently emerged as a powerful new model organism in CNS disease modeling. Here, we exposed zebrafish to 2% glucose and 10% cholesterol for 19 days to experimentally induce type 2 diabetes (DM) and to assess stress responses, microglia, inflammation and apoptosis. We analyzed zebrafish anxiety-like behavior in the novel tank and light-dark box (Days 15-16) tests, as well as examined their biochemical and genomic biomarkers (Day 19). Confirming DM-like state in zebrafish, we found higher whole-body glucose, triglyceride, total cholesterol, low-density lipoprotein levels and glucagon mRNA expression, and lower high-density lipoprotein levels. DM zebrafish also showed anxiety-like behavior, elevated whole-body cortisol and cytokines IFN-γ and IL-4, as well as higher brain mRNA expression of the glucocorticoid receptor, CD11b (a microglial biomarker), pro-inflammatory cytokines IL-6 and TNF-α (but not IL-1β or anti-inflammatory cytokines IL-4 and IL-10), GFAP (an astrocytal biomarker), neurotrophin BDNF, its receptors p75 and TrkB, as well as apoptotic Bax and Caspase-3 (but not BCl-2) genes. Collectively, this supports the overlapping nature of DM-related affective pathogenesis and emphasizes the role of peripheral and central inflammation and apoptosis in DM-related affective and neuroendocrine deficits in zebrafish.

Different doses of methamphetamine alter long-term potentiation, level of BDNF and neuronal apoptosis in the hippocampus of reinstated rats

Methamphetamine (METH) is a psychostimulant. The precise mechanisms of its effects remain unknown and current relapse treatments have low efficacy. However, brain-derived neurotrophic factor (BDNF) and neuronal plasticity are essential contributors, despite paradoxical reports and a lack of comprehensive studies. Therefore, we investigated the effects of different doses of METH on long-term potentiation (LTP), BDNF expression and neuronal apoptosis in the hippocampus of reinstated rats. Rats were injected intraperitoneally with METH (1, 5, or 10 mg/kg) or saline, and trained in a conditioned place preference paradigm. Following implementation of the reinstatement model, electrophysiology, western blotting and TUNEL assay were performed to assess behavior, LTP components, BDNF expression, and neuronal apoptosis, respectively. The results demonstrated that the preference scores, population spike amplitude and BDNF expression markedly decreased in the METH (10 mg/kg) group compared with the other groups. In contrast, METH (5 mg/kg) significantly increased these factors more than the control group. There was no change in variables between METH (1 mg/kg) and the control group. Also, apoptosis of the hippocampus was increased in the METH (10 mg/kg) group compared with the METH (5 mg/kg) group. These results suggest that alterations in synaptic plasticity, expression of BDNF and neuronal apoptosis in the hippocampus has a vital role in the context-induced reinstatement of METH seeking.

Task-Dependent Differences in Operant Behaviors of Rats With Acute Exposure to High Ambient Temperature: A Potential Role of Hippocampal Dopamine Reuptake Transporters

Behavioral or cognitive functions are known to be influenced by thermal stress from the change in ambient temperature (Ta). However, little is known about how increased Ta (i.e., when the weather becomes warm or hot) may affect operant conditioned behavior and the neural substrates involved. The present study thus investigated the effects of high Ta on operant behaviors maintained on a fixed-ratio 1 (FR1) and a differential reinforcement for low-rate responding 10 s (DRL 10-s) schedule of reinforcement. The rats were randomly assigned to three groups receiving acute exposure to Ta of 23°C, 28°C, and 35°C, respectively, for evaluating the effects of high Ta exposure on four behavioral tests. Behavioral responses in an elevated T-maze and locomotor activity were not affected by Ta treatment. Regarding operant tests, while the total responses of FR1 behavior were decreased only under 35°C when compared with the control group of 23°C, those of DRL 10-s behavior were significantly reduced in both groups of 28°C and 35°C. Distinct patterns of inter-response time (IRT) distribution of DRL behavior appeared among the three groups; between-group differences of behavioral changes produced by high Ta exposure were confirmed by quantitative analyses of IRT data. Western blot assays of dopamine (DA) D1 and D2 receptor, DA transporter (DAT) and brain-derived neurotrophic factor (BDNF) were conducted for the sample tissues collected in six brain areas from all the subjects after acute high Ta exposure. Significant Ta-related effects were only revealed in the dorsal hippocampus (dHIP). In which, the DAT levels were increased in a Ta-dependent fashion that was associated with operant behavior changes under high Ta exposure. And, there as an increased level of D1 receptors in the 28°C group. In summary, these data indicate that the performance of operant behavior affected by the present high Ta exposure is task-dependent, and these changes of operant behaviors cannot be attributed to gross motor function or anxiety being affected. The regulation of dHIP DAT may be involved in this operant behavioral change under high Ta exposure.

Interference of norepinephrine transporter trafficking motif attenuates amphetamine-induced locomotor hyperactivity and conditioned place preference

Amphetamine (AMPH)-mediated norepinephrine transporter (NET) downregulation requires NET-T258/S259 trafficking motif. The present study utilizes cell permeable NET-T258/S259 motif interfering peptide, which blocks AMPH-induced NET downregulation, to explore the role of this form of NET regulation in AMPH-mediated behaviors. In rats receiving intra-accumbal microinjections of TAT-conjugated peptides encompassing NET-T258/S259 motif, acute systemic AMPH failed to inhibit NE transport in the TAT-NET-T258/S259 wild-type (WT) peptide injected hemisphere but not in the vehicle or scrambled peptide injected hemisphere. Acute AMPH-induced hyperactivity was significantly reduced in rats receiving intra-accumbal TAT-NET-T258/S259 WT peptide compared to those receiving intra-accumbal vehicle or TAT-NET-T258A/S259A mutant peptide or corresponding TAT-conjugated scrambled peptide. Basal locomotor activity was not altered by peptide infusions alone. Similarly AMPH-induced locomotor sensitization was significantly reduced in rats receiving intra-accumbal TAT-NET-T258/S259 WT peptide prior to AMPH challenge and not in rats receiving the mutant or scrambled peptide. In conditioned place preference (CPP) paradigm, a single bilateral intra-accumbal microinjection of TAT-NET-T258/S259 WT peptide prior to CPP testing significantly reduced AMPH-induced CPP expression. Likewise, a single bilateral intra-accumbal microinjection of TAT-NET-T258/S259 WT peptide prior to drug-challenge significantly attenuated AMPH-primed CPP reinstatement. On the other hand, bilateral intra-accumbal microinjection of scrambled peptide did not affect AMPH-induced CPP expression or reinstatement. These data demonstrate a role for T258/S259-dependent NET regulation in AMPH-induced hyperactivity and sensitization as well as AMPH-induced CPP expression and reinstatement.

Administration of activated glial condition medium in the nucleus accumbens extended extinction and intensified reinstatement of methamphetamine-induced conditioned place preference

Methamphetamine (METH) is a psychostimulant drug with significant abuse potential and neurotoxic effects. A high percentage of users relapse to use after detoxification and no effective medication has been developed for treatment of METH addiction. Developing evidences indicated the role of glial cells in drugs abused related phenomena. However, little is known about the role of these cells in the maintenance and reinstatement of METH-seeking behaviors. Therefore, the current study was conducted to clarify the role of glial cells in the maintenance and reinstatement of METH-induced conditioned place preference (CPP) in rats. Astrocyte condition medium (ACM) and neuroglia conditioned medium (NCM) are liquid mediums prepared from primary astrocyte and neuroglia cells. These mediums seem to contain many factors that release by glia cells. CPP was induced by systemic administration of METH (1mg/kg for 5days, s.c.). Following the establishment of CPP, the rats were given daily bilateral injections (0.5μl/side) of either vehicle, ACM or NCM into the nucleus accumbens (NAc) and then were tested for the maintenance and reinstatement. Intra-NAc administration of ACM treated with METH, could extend the extinction period and also, intensified the magnitude of METH reinstatement. Furthermore, intra-accumbal administration of NCM treated with METH notably delayed the extinction period by four days and significantly increased the magnitude of CPP score in the reinstatement phase compared to the post-test phase. Collectively, these findings suggested that activation of glial cells may be involved in the maintenance and reinstatement of METH-seeking behaviors. It provides new evidence that glia cells might be considered as a potential target for the treatment of METH addiction.

m-Trifluoromethyl-diphenyldiselenide as a pharmacological tool to treat preference symptoms related to AMPH-induced dependence in rats

Amphetamine (AMPH) abuse is a world concern and a serious public health problem. Repeated administration of high doses of AMPH induces neuropsychiatric consequences, including addiction, reward and psychosis, whose pharmacological treatment has shown limited effectiveness. The m-trifluoromethyl-diphenyldiselenide [(m-CF3-PhSe)2] has been documented as a promising pharmacological agent in different animal models related to oxidative damage. In this study, we examined the influence of (m-CF3-PhSe)2 on withdrawal following re-exposure to AMPH. Wistar rats received d,l-AMPH or saline in the conditioned place preference (CPP) paradigm for 8days. Then, half of each initial (AMPH or saline) experimental group was treated with (m-CF3-PhSe)2 or vehicle, resulting in four final groups: i) Saline/vehicle; ii) (m-CF3-PhSe)2/saline; iii) AMPH/vehicle; and iv) AMPH/(m-CF3-PhSe)2. After fourteen days of (m-CF3-PhSe)2 treatment, animals were re-exposed to AMPH or vehicle in the CPP paradigm for three more days in order to assess drug re-conditioning and memory/locomotor activity, performed 24h after AMPH re-exposure in the CPP and the Y maze, respectively. Subsequently, ex-vivo assays were carried out in samples of the prefrontal cortex (PFC) of the animals. The (m-CF3-PhSe)2 treatment was able to prevent AMPH-induced re-conditioning symptoms in rats. Behavioral observations in the Y maze task showed no significant changes. AMPH exposure was able to increase 5-HT uptake as well as oxidative damage in the PFC, whereas (m-CF3-PhSe)2 treatment exerted a preventative effect against these alterations. The current findings suggest that (m-CF3-PhSe)2 might be considered a promising therapeutic tool for AMPH-induced addiction.

Identification of Treatment Targets in a Genetic Mouse Model of Voluntary Methamphetamine Drinking

Methamphetamine has powerful stimulant and euphoric effects that are experienced as rewarding and encourage use. Methamphetamine addiction is associated with debilitating illnesses, destroyed relationships, child neglect, violence, and crime; but after many years of research, broadly effective medications have not been identified. Individual differences that may impact not only risk for developing a methamphetamine use disorder but also affect treatment response have not been fully considered. Human studies have identified candidate genes that may be relevant, but lack of control over drug history, the common use or coabuse of multiple addictive drugs, and restrictions on the types of data that can be collected in humans are barriers to progress. To overcome some of these issues, a genetic animal model comprised of lines of mice selectively bred for high and low voluntary methamphetamine intake was developed to identify risk and protective alleles for methamphetamine consumption, and identify therapeutic targets. The mu opioid receptor gene was supported as a target for genes within a top-ranked transcription factor network associated with level of methamphetamine intake. In addition, mice that consume high levels of methamphetamine were found to possess a nonfunctional form of the trace amine-associated receptor 1 (TAAR1). The Taar1 gene is within a mouse chromosome 10 quantitative trait locus for methamphetamine consumption, and TAAR1 function determines sensitivity to aversive effects of methamphetamine that may curb intake. The genes, gene interaction partners, and protein products identified in this genetic mouse model represent treatment target candidates for methamphetamine addiction.

The Effects of BDNF Val66Met Gene Polymorphism on Serum BDNF and Cognitive Function in Methamphetamine-Dependent Patients and Normal Controls: A Case-Control Study

Studies suggest that a functional polymorphism of the brain-derived neurotrophic factor gene (BDNF Val66Met) may contribute to methamphetamine dependence. We hypothesized that this polymorphism had a role in cognitive deficits in methamphetamine-dependent patients and in the relationship of serum BDNF with cognitive impairments. We conducted a case-control study by assessing 194 methamphetamine-dependent patients and 378 healthy volunteers without history of drug use on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the presence of the BDNF Val66Met polymorphism and serum BDNF levels. We showed no significant differences in genotype and allele distributions between the methamphetamine-dependent patients and controls. Some aspects of cognitive function significantly differed in the 2 groups. The serum BDNF levels in methamphetamine-dependent patients were significantly higher than those of the healthy controls. In the patients, partial correlation analysis showed a significant positive correlation between serum BDNF and the delayed memory index score. The RBANS scores showed statistically significant BDNF level × genotype interaction. Further regression analyses showed a significant positive association between BDNF levels and the RBANS total score, immediate memory or attention index among Val homozygote patients, whereas a significant negative association of BDNF levels with the RBANS total score, visuospatial/constructional, or language index was found among Met/Val heterozygous patients. We demonstrated significant impairment on some aspects of cognitive function and increased BDNF levels in methamphetamine-dependent patients as well as genotypic differences in the relationships between BDNF levels and RBANS scores on the BDNF Val66Met polymorphism only in these patients.