AB1779SP Sigma-AldrichAnti-Brain Derived Neurotrophic Factor Antibody

Social defeat stress induces persistent cross-sensitization to psychostimulants, but the molecular mechanisms underlying the development of cross-sensitization remain unclear. One candidate is brain-derived neurotrophic factor (BDNF). The present research examined whether ventral tegmental area (VTA) BDNF overexpression would prolong the time course of cross-sensitization after a single social defeat stress, which normally produces transient cross-sensitization lasting less than 1 week. ΔFosB, a classic molecular marker of addiction, was also measured in mesocorticolimbic terminal regions. Separate groups of intact male Sprague-Dawley rats underwent a single episode of social defeat stress or control handling, followed by amphetamine (AMPH) challenge 3 or 14 days later. AMPH cross-sensitization was apparent 3, but not 14, days after stress. Intra-VTA infusion of adeno-associated viral (AAV-BDNF) vector resulted in a twofold increase of BDNF level in comparison to the group receiving the control virus (AAV-GFP), which lasted at least 45 days. Additionally, overexpression of BDNF in the VTA alone increased ΔFosB in the nucleus accumbens (NAc) and prefrontal cortex. Fourteen days after viral infusions, a separate group of rats underwent a single social defeat stress or control handling and were challenged with AMPH 14 and 24 days after stress. AAV-BDNF rats exposed to stress showed prolonged cross-sensitization and facilitated sensitization to the second drug challenge. Immunohistochemistry showed that the combination of virally enhanced VTA BDNF, stress, and AMPH resulted in increased ΔFosB in the NAc shell compared with the other groups. Thus, elevation of VTA BDNF prolongs cross-sensitization, facilitates sensitization, and increases ΔFosB in mesocorticolimbic terminal regions. As such, elevated VTA BDNF may be a risk factor for drug sensitivity.

Ketamine is an anesthetic and a popular abusive drug. As an anesthetic, effects of ketamine on glutamate and GABA transmission have been well documented but little is known about its long-term effects on the dopamine system. In the present study, the effects of ketamine on dopamine were studied in vitro and in vivo. In pheochromocytoma (PC 12) cells and NGF differentiated-PC 12 cells, ketamine decreased the cell viability while increasing dopamine (DA) concentrations in a dose-related manner. However, ketamine did not affect the expression of genes involved in DA synthesis. In the long-term (3 months) ketamine treated mice, significant increases of DA contents were found in the midbrain. Increased DA concentrations were further supported by up-regulation of tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis. Activation of midbrain dopaminergic neurons could be related to ketamine modulated cortical-subcortical glutamate connections. Using western blotting, significant increases in BDNF protein levels were found in the midbrain, suggesting that perhaps BDNF pathways in the cortical-subcortical connections might contribute to the long-term ketamine induced TH upregulation. These data suggest that long-term ketamine abuse caused a delayed and persistent upregulation of subcortical DA systems, which may contribute to the altered mental status in ketamine abusers.

Behavioral sensitization, or augmented locomotor response to successive drug exposures, results from neuroadaptive changes contributing to addiction. Both the medial prefrontal cortex (mPFC) and ventral tegmental area (VTA) influence behavioral sensitization and display increased immediate-early gene and BDNF expression after psychostimulant administration. Here we investigate whether mPFC neurons innervating the VTA exhibit altered Fos or BDNF expression during long-term sensitization to amphetamine. Male Sprague-Dawley rats underwent unilateral intra-VTA infusion of the retrograde tracer Fluorogold (FG), followed by 5 daily injections of either amphetamine (2.5 mg/kg, i.p.) or saline vehicle. Four weeks later, rats were challenged with amphetamine (1.0 mg/kg, i.p.) or saline (1.0 mL/kg, i.p.). Repeated amphetamine treatment produced locomotor sensitization upon drug challenge. Two hours later, rats were euthanized, and mPFC sections were double-immunolabeled for either Fos-FG or Fos-BDNF. Tissue from the VTA was also double-immunolabeled for Fos-BDNF. Amphetamine challenge increased Fos and BDNF expression in the mPFC regardless of prior drug experience, and further augmented mPFC BDNF expression in sensitized rats. Similarly, more Fos-FG and Fos-BDNF double-labeling was observed in the mPFC of sensitized rats compared to drug-naïve rats after amphetamine challenge. Repeated amphetamine treatment also increased VTA BDNF, while both acute and repeated amphetamine treatment increased Fos and Fos-BDNF co-labeling, an effect enhanced in sensitized rats. These findings point to a role of cortico-tegmental BDNF in long-term amphetamine sensitization.

Degeneration of locus coeruleus (LC) noradrenergic forebrain projection neurons is an early feature of Alzheimer's disease. The physiological consequences of this phenomenon are unclear, but observations correlating LC neuron loss with increased Alzheimer's disease pathology in LC projection sites suggest that noradrenaline (NA) is neuroprotective. To investigate this hypothesis, we determined that NA protected both hNT human neuronal cultures and rat primary hippocampal neurons from amyloid-beta (Abeta(1-42) and Abeta(25-35)) toxicity. The noradrenergic co-transmitter galanin was also effective at preventing Abeta-induced cell death. NA inhibited Abeta(25-35)-mediated increases in intracellular reactive oxygen species, mitochondrial membrane depolarization, and caspase activation in hNT neurons. NA exerted its neuroprotective effects in these cells by stimulating canonical beta(1) and beta(2) adrenergic receptor signaling pathways involving the activation of cAMP response element binding protein and the induction of endogenous nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Treatment with functional blocking antibodies for either NGF or BDNF blocked NA's protective actions against Abeta(1-42) and Abeta(25-35) toxicity in primary hippocampal and hNT neurons, respectively. Taken together, these data suggest that the neuroprotective effects of noradrenergic LC afferents result from stimulating neurotrophic NGF and BDNF autocrine or paracrine loops via beta adrenoceptor activation of the cAMP response element binding protein pathway.

Using in vivo electrophysiological techniques and continuous local infusion methods, we examined the effects of brain-derived neurotrophic factor (BDNF) and its specific antibody (anti-BDNF) on the noradrenergic axon terminals of the locus coeruleus (LC) neurons in the frontal cortex of aging rats. Recently, we observed that LC neurons with multiple-threshold antidromic responses (multi-threshold LC neurons) increased critically between 15 and 17 months of age. To examine whether the BDNF is involved in this change occurred in the aging brain, we continuously infused BDNF into the frontal cortex for 14 days. Exogenous BDNF produced a marked increase in the multi-threshold LC neurons in the 13-month-old brain, accompanied with a decrease in threshold current. However, no morphological change in the noradrenergic axons was observed in the BDNF-infused cortex. In contrast, infusion of anti-BDNF led to a dose-dependent reduction of the multi-threshold LC neurons in the 19-month-old brain, accompanied with an increase in threshold current. These findings suggest that BDNF may contribute to functional changes in the presynaptic axon terminals of LC neurons in the aging brain.

In a previous study we have shown that a subpopulation of primary sensory neurons contain brain-derived neurotrophic factor immunoreactivity. In the present study we investigated the distribution of brain-derived neurotrophic factor and its mRNA in cranial and spinal ganglia at different segmental levels, using immunohistochemical and quantitative reverse transcriptase-polymerase chain reaction techniques. Our results show that there is no significant difference in the percentage of brain-derived neurotrophic factor-immunoreactive neurons in spinal ganglia of different segmental levels. In contrast, more brain-derived neurotrophic factor-immunoreactive neurons were found in placode-derived than neural crest-derived ganglia. The percentage of brain-derived neurotrophic factor-immunoreactive neurons is consistent with the percentage of neurons lost after deletion of brain-derived neurotrophic factor or trkB genes. However, there is no correlation between brain-derived neurotrophic factor mRNA levels and the number of brain-derived neurotrophic factor immunoreactive neurons in these ganglia, suggesting that some neurons synthesize brain-derived neurotrophic factor while others accumulate the factor following its retrograde transport within nerve fibers. In particular, the proportion of brain-derived neurotrophic factor that is derived from extraganglionic sources in the placode-derived ganglia appears greater than that in the neural crest-derived ganglia.

Neurotrophins are a family of proteins which act as survival and differentiative factors in the developing and mature nervous system. Extensive evidence has been provided for their retrograde action following incorporation into nerve terminals and transport to the cell body. In contrast, we now demonstrate that one neurotrophin, brain-derived neurotrophic factor, is transported anterogradely via both peripheral and central processes of spinal sensory neurons. Using newly generated antisera, we have examined the distribution of brain-derived neurotrophic factor immunoreactivity and found it to be present within a subpopulation of sensory somata, primarily those with a small-to-medium diameter. The immunoreactivity was accumulated on both the distal and proximal sides of a ligature on the sciatic nerve. The accumulation on the distal side, but not on the proximal side, was substantially reduced by pretreatment with brain-derived neurotrophic factor antibodies in vivo. In contrast to the periphery, the immunoreactivity only accumulated on the proximal side of a lesion of the dorsal root. In the spinal cord, most nerve terminals immunoreactive for brain-derived neurotrophic factor were identified in lamina II. Lesion of the dorsal root led to a reduction of these nerve terminals. These studies indicate that the factor is transported not only retrogradely to, but also anterogradely from, the spinal ganglia to terminals in the periphery and spinal cord. The findings add a new dimension to the role of neuronal growth factors, since anterograde transport has not been observed previously for any endogenous survival factor.