The purpose was to analyze the role of dopamine D1 and D2 receptors in conditioned place preference (CPP) of a relatively high dose (5 mg/kg) of methylphenidate (MPH) in adolescent male and female rats, as well as the role of these receptors in the effects of MPH on brain-derived neurotrophic factor (BDNF). The primary mechanism of MPH in the brain is the blockade of the dopamine transporter, yielding an increase of dopamine in the synaptic cleft and is the basis for the rewarding properties of MPH. An initial preference given on postnatal day (P)32 yielded no preference for any context in a three-chambered shuttle box with removable dividers, thus, a biased procedure was used. Conditioning began the day after the initial preference test on P33. On conditioning trials, animals were first administered saline or their respective antagonist (D1 antagonist: 0.1 or 0.2 mg/kg SCH-23390; D2 antagonist: 0.01 or 0.03 mg/kg Eticlopride HCl), followed by methylphenidate (MPH; 5mg/kg). Approximately 10 min after MPH administration, rats were placed into the paired context for a 10 min trial. The choice of the paired context was balanced across animals. In a separate session, all animals received saline in the opposing context. One day post-conditioning on P38, a preference test was administered with dividers removed. Preference was determined through the amount of time spent in the paired context as compared to time spent in the unpaired context on the post-conditioning preference test. One day following the preference test on P39, brain tissue was removed, and nucleus accumbens and striatum analyzed for BDNF. Results showed that MPH produced an increased preference on the post-conditioning preference test that was blocked by either dose of SCH-23390, but was not affected by either dose of eticlopride. Additionally, the higher dose of SCH-23390 resulted in a conditioned place aversion in males, which may be due to the increased presence of dopamine D1 receptors in adolescent males. MPH produced a robust significant increase in BDNF in both nucleus accumbens and striatum, and this increase was alleviated by SCH-23390, but the effect on BDNF is still to be analyzed relative to D2 antagonism. These results show that MPH results in a conditioned place preference in adolescent male and female rats, and these effects appear to be mediated by the dopamine D1 receptor. Further, MPH results in a significant increase of BDNF in drug reward areas of the brain, which has implications towards synaptic plasticity in these regions in response to MPH.

In the USA, approximately 15% of women smoke tobacco cigarettes during pregnancy. In utero tobacco smoke exposure produces somatic growth deficits like intrauterine growth restriction and low birth we

Methylphenidate (MPH) is a psychostimulant that is used for the treatment of attention-deficit hyperactivity disorder that is often recreationally abused. Past studies have primarily analyzed the effects of MPH on behavior and BDNF using males as subjects, with studies showing a lack of behavioral sensitization, although the effect of MPH on BDNF has yielded contradictory results. BDNF is a neurotrophin ubiquitously found throughout the brain that plays an important role in synaptic maintenance and development and has been implicated in addiction. This study analyzed sex differences in induction and expression of MPH locomotor sensitization in adolescent male and female rats as well as the effects of MPH on BDNF protein in two brain areas of drug reward: the nucleus accumbens (NAcc) and striatum (STR), after both induction and expression of sensitization. After habituation to a locomotor arena, animals (N=6-8 per group) were administered MPH (5 mg/kg) or saline every other day from postnatal day (P)33 to 49 and tested for 30 min in the same arena with activity counts recorded. In one group, brain tissue was removed one day following testing and the NAcc and STR assayed for BDNF at P50. A different group of animals was raised to P60 and given an MPH (or saline) challenge. One day following the challenge, brain tissue was removed and the NAcc and STR were assayed for BDNF at P61. Females administered MPH demonstrated behavioral sensitization from P33 to P41, and then decreased in activity from P41 to P49. Females demonstrated a robust increase in locomotor activation as compared to males, which failed to demonstrate sensitization to MPH. However, both groups given MPH demonstrated an increase in activity compared to controls throughout sensitization testing. On the challenge at P60, females administered MPH demonstrated higher levels of activity compared to all other groups and were equivalent to their final day of sensitization. Males administered MPH also expressed sensitization, as they demonstrated increased behavioral activation as compared to saline-treated controls. Neurochemical analyses at P50 revealed that MPH produced a significant increase in striatal BDNF in males, but a significant decrease in striatal BDNF in females. There were no changes in the NAcc. At P61, BDNF was increased in both STR and NAcc in males, and female data will be presented. These data demonstrate robust sex differences in behavioral activation and sensitization to MPH that is both induced and expressed in females, but only expressed in males. Further, MPH produces sex-dependent effects on BDNF, indicating sex differences in the brain plasticity response to MPH in adolescence.

This study analyzed locomotor sensitization to methylphenidate (MPH, Trade name: Ritalin) in adolescent male and female rats. Females, but not males, demonstrated locomotor sensitization. Interestingly, females given MPH demonstrated a significant decrease of brain derived neurotrophic factor (BDNF) in the striatum, whereas males demonstrated an increase in this same brain area.

Myocardial infarction (MI) induced heart failure (HF) is a leading cause of morbidity and mortality over the world. Regular exercise improves quality of life and decreases hospitalization and mortality of patients with HF. In animals, exercise post MI attenuates progressive cardiac remodeling and cardiac dysfunction, and decreases neuronal activity in the paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM), which are key brain nuclei contributing to sympathetic hyperactivity post MI. The peripheral and central molecular mechanisms underlying these beneficial effects of exercise are not well understood. We studied one possible mechanism, brain-derived neurotrophic factor (BDNF), an exercise-induced factor, which via binding to its receptor tropomyosin-related kinase B (TrkB) may contribute to improvement of cardiac function post MI. In the brain, the ratio between two isoforms of the TrkB receptor, full-length and truncated forms (TrkB.FL/TrkB.T1) determines the extent of intracellular responses to mature BDNF (mBDNF; an active form of BDNF) and a decrease in this ratio may reflect down-regulation of BDNF-TrkB.FL signaling. Ca2+/calmodulin-dependent kinase II (CaMKII) and protein kinase B (Akt) are intracellular factors of BDNF-TrkB signaling in hippocampal/cortical neurons. Activation of cardiac BDNF-TrkB signaling may increase cardiomyocyte survival and myocardial contractility. In hypertensive rats, the role of BDNF-TrkB signaling in the PVN and RVLM appears opposite with activation of this axis in the PVN increasing, but in the RVLM decreasing sympathetic nerve activity (SNA). However, activation of CaMKII and Akt in the PVN and RVLM both mediate increase in SNA. The specific role of BDNF-TrkB signaling in the PVN and RVLM of rats with HF post MI has not yet been studied. We hypothesized that exercise training post MI enhances BDNF-TrkB signaling pathways in the left ventricle (LV) and RVLM, but inhibits in the PVN, and thereby preserves cardiac structure and function post MI. We evaluated changes in BDNF-TrkB axis and intracellular factors CaMKII and Akt in the non-infarct area of the LV, PVN and RVLM in sedentary and exercising rats with MI. The impact of systemic blockade of BDNF-TrkB signaling was assessed with ANA-12, a selective non-competitive antagonist of TrkB receptors. In the infarct area of the LV, mBDNF protein decreased and TrkB.T1 protein increased. In the non-infarct area, mBDNF tended to be decreased without change in TrkB.T1 expression. The activities of CaMKII and Akt were decreased in the non-infarct area of the LV. In the PVN and RVLM, the TrkB.FL/TrkB.T1 ratio was decreased but without changes in mBDNF and downstream factors except for decrease in Akt activity in the RVLM. Exercise training improved ejection fraction (EF), cardiac index and LV end-diastolic pressure, but only the exercise-induced improvement of EF was blocked by ANA-12. In the non-infarct area of the LV, exercise prevented decreases in mBDNF, CaMKII and Akt, and these effects were prevented by ANA-12. In the PVN, exercise increased mBDNF and decreased Akt activity, whereas in the RVLM, exercise had no effect on mBDNF but decreased CaMKII activity. The exercise-induced increase mBDNF in the PVN and decrease in p-CaMKIIβ expression in the RVLM were prevented by ANA-12. Our findings suggest that down-regulation of BDNF-TrkB signaling post MI is prominent in the LV with decreases in mBDNF protein in the infarct area and intracellular factors CaMKII and Akt in the non-infarct area. Increases in mBDNF, CaMKII and Akt in the LV by exercise may contribute to improvement of EF. In the PVN and RVLM, despite a decrease in the ratio of TrkB.FL/TrkB.T1 in both brain nuclei, only Akt activity decreased in the RVLM post MI. Exercise-induced decreases in activities of CaMKII in the RVLM and Akt in the PVN may both contribute to reduction in sympathetic hyperactivity post MI.

Macrophages (monocytes/microglia) could play a critical role in central nervous system repair. We have previously found a synchronism between the regression of spontaneous axonal regeneration and the deactivation of macrophages 34 wk after a compression-injury of rat spinal cord. To explore whether reactivation of endogenous macrophages might be beneficial for spinal cord repair, we have studied the effects of granulocyte-macrophage colony stimulating factor (GM-CSF) in the same paraplegia model and in cell cultures. There is significant, though transient, improvement of locomotor recovery after a single delayed intraperitoneal injection of 2g GM-CSF. This improvement is associated with an increased expression of 5HT at the level of the CPG (T13-L2). At longer survival delays, axonal regeneration is significantly enhanced in GM-CSF-treated rats. We then studied the effects of GM-CSF on brain-derived neurotrophic factor (BDNF)secretion by macrophages/microglia, inflammatory reaction and phagocytosis by macrophages/microglia. In vivo, at short post-treatment delays, we found that GM-CSF increases significantly the expression of Cr3 and BDNF by macrophages at the lesion site. In vitro, BV2 microglial cells expressed higher levels of BDNF in the presence of GM-CSF and neurons cocultured with microglial cells activated by GM-CSF generated more neurites, an effect blocked by a BDNF antibody. In vivo, we showed that GM-CSF treatment (either immediate or delayed) does not increase IL-6 expression by macrophages/microglia or astrocytes. We showed that a delayed GM-CSF treatment down regulates IL-1 expression by astrocytes. In vivo, we showed that a delayed GM-CSF treatment can decrease MAG expression at the lesion site. These experiments suggest that GM-CSF could be an interesting treatment option for spinal cord injury and that its beneficial effects might be mediated by BDNF.

Voluntary wheel running is rewarding and believed to activate the same brain reward system as in alcohol and drug addiction. Brain-derived neurotrophic factor (BDNF), a well-known growth factor widely expressed in the brain, is modulated by both voluntary exercise and alcohol consumption. The aim of this study was to evaluate how voluntary exercise affects the expression levels of BDNF and its receptor TrkB in brain regions involved in positive and negative reinforcement. Additionally we wanted to evaluate the effect it may have on alcohol drinking behaviors in C57BL/6 mice, a mouse model which are naturally prone for engaging in voluntary exercise and voluntary alcohol consumption. We found a small upregulation in DG and CA1 after three weeks of exercise, confirming findings by others, and a significant 3-fold downregulation of BDNF in NAc after both three weeks of exercise and exercise followed by a five week period of either ethanol intake or not. Interestingly, we here show a significant 100-fold increase in BDNF after exercise and a 120-fold increase after both exercise and alcohol consumption in amygdala, a region involved in regulation of anxiety-related behavior and negative reinforcement. Additionally a slightly lower 10-fold increase in BDNF was seen after exercise and a 15-fold increase after exercise followed by ethanol in prefrontal cortex, a structure contributing to reward-related behavior. Behaviorally, we could not either directly following exercise or at five weeks post-exercise detect any significant effect of wheel-running on depression-related behavior. However, we did find that exercise significantly increased the alcohol intake.

Experience drives changes in gene expression that mold and reorganize neuronal circuits. In response to neuronal activity, the transcription factor CREB binds to a regulatory site on Bdnf promoter IV to modulate BDNF protein levels. CREB and BDNF are extensively implicated in animal behaviour, but the role of the interaction between these proteins has not been studied. I used transgenic mice carrying mutations at the CREB binding site of Bdnf promoter IV (CREmKI mutation) to specifically disrupt this interaction. F1 (N = 52) and F2 (N = 69) mice underwent a battery of behavioural tests. All mice showed normal motor learning and spatial memory. Critically, F1 mutants showed impaired auditory fear memory, while F2 mutants showed heightened anxiety. I suspect that differences in Bdnf expression and compensatory effects contributed to discrepancies between the two generations. My findings highlight the relevance of BDNF expression levels for memory- and anxiety-related behaviours.

Experience drives changes in gene expression that mold and reorganize neuronal circuits. In response to neuronal activity, the transcription factor CREB binds to a regulatory site on Bdnf promoter IV to modulate BDNF protein levels. CREB and BDNF are extensively implicated in animal behaviour, but the role of the interaction between these proteins has not been studied. I used transgenic mice carrying mutations at the CREB binding site of Bdnf promoter IV (CREmKI mutation) to specifically disrupt this interaction. F1 (N = 52) and F2 (N = 69) mice underwent a battery of behavioural tests. All mice showed normal motor learning and spatial memory. Critically, F1 mutants showed impaired auditory fear memory, while F2 mutants showed heightened anxiety. I suspect that differences in Bdnf expression and compensatory effects contributed to discrepancies between the two generations. My findings highlight the relevance of BDNF expression levels for memory- and anxiety-related behaviours.

Recently, it has been suggested that neurodevelopmental abnormalities underlie schizophrenia. However, it has also been suggested that schizophrenia is a neurodegenerative disease as evidenced by a progressive worsening of symptoms over time. Neurodevelopmental abnormalities may, therefore, create a functionally compromised system that is more susceptible to neuronal atrophy and/or death caused by environmental factors such as stress (a known precipitant of acute psychotic episodes and exacerbant of schizophrenia). This hypothesis was tested using the putative neurodevelopmental model of schizophrenia described by Lipska 'et al'. (1993). The effects of neonatal hippocampal lesions on BDNF mRNA and NMDAR1 mRNA, factors involved in development, cell survival and cell communication, were investigated in adult rats following exposure to a physiological stressor. Apoptosis levels were also investigated in these rats to determine if neurodegeneration was present. Results demonstrate that BDNF mRNA was reduced in the prefrontal cortex and hippocampus of lesioned as compared to sham rats. Increased BNDF mRNA resulted from swim stress in both groups, but the increase in lesioned animals was more pronounced than controls. NMDAR1 mRNA was also reduced in the prefrontal cortex and CA3 and CA1 regions of the hippocampus in lesioned versus sham rats. There was an increase, however, in the dentate gyrus of lesioned versus sham rats. Swim stress increased NMDAR1 mRNA in the prefrontal cortex and decreased it in the hippocampus. There was also an increase in apoptosis in lesioned versus sham rats, with no significant increase in response to stress. Reductions in BDNF mRNA in lesioned versus control animals support the hypothesis that neurodevelopmental lesions may result in a system more susceptible to stressors. Reductions in NMDAR1 mRNA are in accordance with the NMDA glutamate receptor hypofunction theory of schizophrenia. It is possible that reductions in glutamate function can remove the inhibitory effect of GABA, thereby resulting in overexcitation of the system and a potential for neurodegeneration. Increased apoptosis supports the presence of neurodegeneration as an ongoing phenomenon. Even though the effect of acute stress on apoptosis was not significant, the very small increases demonstrated can have significant functional consequences over extended periods of time.