Mice experiencing repeated aggression develop a long-lasting aversion to social contact, which can be normalized by chronic, but not acute, administration of antidepressant. Using viral-mediated, mesolimbic dopamine pathway-specific knockdown of brain-derived neurotrophic factor (BDNF), we showed that BDNF is required for the development of this experience-dependent social aversion. Gene profiling in the nucleus accumbens indicates that local knockdown of BDNF obliterates most of the effects of repeated aggression on gene expression within this circuit, with similar effects being produced by chronic treatment with antidepressant. These results establish an essential role for BDNF in mediating long-term neural and behavioral plasticity in response to aversive social experiences.

A single exposure to cocaine rapidly induces the brief activation of several immediate early genes, but the role of such short-term regulation in the enduring consequences of cocaine use is poorly understood. We found that 4 h of intravenous cocaine self-administration in rats induced a transient increase in brain-derived neurotrophic factor (BDNF) and activation of TrkB-mediated signaling in the nucleus accumbens (NAc). Augmenting this dynamic regulation with five daily NAc BDNF infusions caused enduring increases in cocaine self-administration, and facilitated relapse to cocaine seeking in withdrawal. In contrast, neutralizing endogenous BDNF regulation with intra-NAc infusions of antibody to BDNF subsequently reduced cocaine self-administration and attenuated relapse. Using localized inducible BDNF knockout in mice, we found that BDNF originating from NAc neurons was necessary for maintaining increased cocaine self-administration. These findings suggest that dynamic induction and release of BDNF from NAc neurons during cocaine use promotes the development and persistence of addictive behavior.

Brain-derived neurotrophic factor has been associated previously with the regulation of food intake. To help elucidate the role of this neurotrophin in weight regulation, we have generated conditional mutants in which brain-derived neurotrophic factor has been eliminated from the brain after birth through the use of the cre-loxP recombination system. Brain-derived neurotrophic factor conditional mutants were hyperactive after exposure to stressors and had higher levels of anxiety when evaluated in the light/dark exploration test. They also had mature onset obesity characterized by a dramatic 80-150% increase in body weight, increased linear growth, and elevated serum levels of leptin, insulin, glucose, and cholesterol. In addition, the mutants had an abnormal starvation response and elevated basal levels of POMC, an anorexigenic factor and the precursor for alpha-MSH. Our results demonstrate that brain derived neurotrophic factor has an essential maintenance function in the regulation of anxiety-related behavior and in food intake through central mediators in both the basal and fasted state.

Brain-derived neurotrophic factor (BDNF) is involved in synaptic plasticity, neuronal differentiation and survival of neurons. Observations of decreased serum BDNF levels in patients with neuropsychiatric disorders have highlighted the potential of BDNF as a biomarker, but so far there have been no studies directly comparing blood BDNF levels to brain BDNF levels in different species. We examined blood, serum, plasma and brain-tissue BDNF levels in three different mammalian species: rat, pig, and mouse, using an ELISA method. As a control, we included an analysis of blood and brain tissue from conditional BDNF knockout mice and their wild-type littermates. Whereas BDNF could readily be measured in rat blood, plasma and brain tissue, it was undetectable in mouse blood. In pigs, whole-blood levels of BDNF could not be measured with a commercially available ELISA kit, but pig plasma BDNF levels (mean 994±186 pg/ml) were comparable to previously reported values in humans. We demonstrated positive correlations between whole-blood BDNF levels and hippocampal BDNF levels in rats (r2=0.44, p=0.025) and between plasma BDNF and hippocampal BDNF in pigs (r2=0.41, p=0.025). Moreover, we found a significant positive correlation between frontal cortex and hippocampal BDNF levels in mice (r2=0.81, p=0.0139). Our data support the view that measures of blood and plasma BDNF levels reflect brain-tissue BDNF levels.

Brain-derived neurotrophic factor (BDNF) and its receptor TrkB are expressed in several hypothalamic and hindbrain nuclei involved in regulating energy homeostasis, developmentally and in the adult animal. Their depletion during the fetal or early postnatal periods when developmental processes are still ongoing elicits hyperphagic behavior and obesity in mice. Whether BDNF is a chief element in appetite control in the mature brain remains controversial. The required sources of this neurotrophin are also unknown. We show that glucose administration rapidly induced BDNF mRNA expression, mediated by Bdnf promoter 1, and TrkB transcription in the ventromedial hypothalamus (VMH) of adult mice, consistent with a role of this pathway in satiety. Using viral-mediated selective knock-down of BDNF in the VMH and dorsomedial hypothalamus (DMH) of adult mice, we were able to elucidate the physiological relevance of BDNF in energy balance regulation. Site-specific mutants exhibited hyperphagic behavior and obesity but normal energy expenditure. Furthermore, intracerebroventricular administration of BDNF triggered an immediate neuronal response in multiple hypothalamic nuclei in wild-type mice, suggesting that its anorexigenic actions involve short-term mechanisms. Locomotor, aggressive, and depressive-like behaviors, all of which are associated with neural circuits involving the VMH, were not altered in VMH/DMH-specific BDNF mutants. These findings demonstrate that BDNF is an integral component of central mechanisms mediating satiety in the adult mouse and, moreover, that its synthesis in the VMH and/or DMH is required for the suppression of appetite.

Brain-derived neurotrophic factor has been associated previously with the regulation of food intake. To help elucidate the role of this neurotrophin in weight regulation, we have generated conditional mutants in which brain-derived neurotrophic factor has been eliminated from the brain after birth through the use of the cre-loxP recombination system. Brain-derived neurotrophic factor conditional mutants were hyperactive after exposure to stressors and had higher levels of anxiety when evaluated in the light/dark exploration test. They also had mature onset obesity characterized by a dramatic 80-150% increase in body weight, increased linear growth, and elevated serum levels of leptin, insulin, glucose, and cholesterol. In addition, the mutants had an abnormal starvation response and elevated basal levels of POMC, an anorexigenic factor and the precursor for alpha-MSH. Our results demonstrate that brain derived neurotrophic factor has an essential maintenance function in the regulation of anxiety-related behavior and in food intake through central mediators in both the basal and fasted state.

The self-renewal and differentiation of haematopoietic stem cells occurs in vivo and in vitro in direct contact with cells making up the haematopoietic microenvironment. In this study we used adhesive ligands and blocking antibodies to identify stromal cell-derived extracellular matrix proteins involved in promoting attachment of murine haematopoietic stem cells. Here we report that day-12 colony-forming-unit spleen (CFU-S12)5 cells and reconstituting haematopoietic stem cells attach to the C-terminal, heparin-binding fragment of fibronectin by recognizing the CS-1 peptide of the alternatively spliced non-type III connecting segment (IIICS) of human plasma fibronectin. Furthermore, CFU-S12 stem cells express the alpha 4 subunit of the VLA-4 integrin receptor, which is known to be a receptor for the CS-1 sequence, and monoclonal antibodies against the integrin alpha 4 subunit of VLA-4 block adhesion of CFU-S12 stem cells to plates coated with the C-terminal fibronectin fragment. Finally, polyclonal antibodies against the integrin beta 1 subunit of VLA-4 inhibit the formation of CFU-S12-derived spleen colonies and medullary haematopoiesis in vivo following intravenous infusion of antibody-treated bone marrow cells.

Neurotrophin-3 (NT-3) is a member of the neurotrophin family, which includes nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5). These factors are crucial for development of the peripheral nervous system 1 , but not the central nervous system (CNS), except that NT-3 and BDNF have been implicated in the postnatal development of the cerebellum 2,3 . Here we created a conditional NT-3-deficient mutant, which showed abnormal cerebellar morphology.Postnatal cerebellar development, which involves active proliferation and migration of neuronal precursors, is complete by postnatal day 21 (P21) in the mouse 4 . During this period, the neurotrophins BDNF and NT-3 are highly expressed in the cerebellum 5,6 . BDNF-deficient mutants generally die within the first two weeks of life, but cerebellar development can be assessed during this time window 7 . NT-3 -deficient mutants, on the other hand, rarely survive past P1 (ref. 8), preventing a meaningful assessment of postnatal cerebellar development. To circumvent this problem, we used the phage P1 cre recombinase-loxP system 9 to create an NT-3 conditional mutant that was viable, yet lacked NT-3 expression in the CNS.A targeting vector ( Fig. 1a) designed to introduce loxP sites around the NT-3 coding exon (exon II) 10 was transfected into embryonic stem cells. The selection cassette was removed from homologously targeted clones by transient transfection of a cre recombinase expression vector, leaving loxP sites surrounding exon II ( Fig. 1c; data not shown). Embryonic stem cells carrying this new allele of NT-3, referred to as NT-3 2lox , were used to generate a mouse line (data not shown). Mice bearing the NT-3 2lox allele were intercrossed, generating viable and fertile NT-3 2lox/2lox homozygotes, without behavioral abnormalities (data not shown). To delete NT-3 in the CNS, we crossed NT-3 2lox/+ mice to a transgenic strain bearing the cre recombinase gene expressed under the control of the rat nestin promoter/intron 2 enhancer (A.T., unpublished data). Nestin-cre-mediated recombination resulted in the deletion of NT-3 exon II, leaving a single loxP site remaining in the genome (Fig 1c). As exon II contains the entire coding sequence of the protein, this NT-3 1lox allele is equivalent to the NT-3-null mutation 8 . Southern blot analysis detected cre-mediated recombination in whole embryos as early as 9.5 days post coitum (E9.5). Recombination increased during embryonic development such that it was nearly complete in brain and spinal cord by E15.5, whereas other tissues showed a much smaller extent of recombination (Fig. 2a). In adults, incomplete recombination was detected in a number of tissues, but the NT-3 2lox allele was almost fully recombined in the CNS (Fig. 2b) and in the germ line of mice that carried the nestin-cre transgene (data not shown). Therefore, to generate NT-3 conditional mutants, NT-3 2lox/+ males bearing the nestin-cre transgene were crossed to NT-3 2lox/+ nontransgenic females. Conditional mutants generate...