title: Loss of brain-derived neurotrophic factor gene allele exacerbates brain monoamine deficiencies and increases stress abnormalities of serotonin transporter knockout mice.
abstract: To study the neurochemical and behavioral effects of altered brain-derived neurotrophic factor (BDNF) expression on a brain serotonin system with diminished serotonin transport capability, a double-mutant mouse model was developed by interbreeding serotonin transporter (SERT) knockout mice with BDNF heterozygous knockout mice (BDNF +/-), producing SERT -/- x BDNF +/- (sb) mice. Prior evidence implicates serotonin and SERT in anxiety and stress responses. Some studies have shown that BDNF supports serotonergic neuronal development, leading to our hypothesis that reduced BDNF availability during development might exaggerate the consequences of absent SERT function. In the present study, brain serotonin and 5-hydroxyindol acetic acid concentrations in male sb mice were significantly reduced in the hippocampus and hypothalamus compared with wild-type control SB mice, BDNF-deficient Sb mice, and serotonin transporter knockout sB mice. The sb mice had significantly increased anxiety-like behaviors compared with SB, Sb, and sB mice as measured on the elevated plus maze test. These sb mice also had significantly greater increases in plasma adrenocorticotrophic hormone than mice with other genotypes after a stressful stimulus. Analysis of neuronal morphology showed that hypothalamic and hippocampal neurons exhibited 25-30% reductions in dendrites in sb mice compared with SB control mice. These findings support the hypothesis that genetic changes in BDNF expression interact with serotonin and other circuits that modulate anxiety and stress-related behaviors. Thus, this double-mutant mouse model should prove valuable in studying other gene x gene consequences for brain plasticity as well as in evaluating epistatic interactions of BDNF and serotonin transporter gene polymorphisms in neuropsychiatric disorders.
authors.affiliation: Laboratory of Clinical Science, NIMH, NIH, Bethesda, MD 20892-1264, USA. renpatr@intra.nimh.nih.gov
authors.forename: Renee F
authors.initials: RF
authors.lastname: Ren-Patterson
authors.forename: Lauren W
authors.initials: LW
authors.lastname: Cochran
authors.forename: Andrew
authors.initials: A
authors.lastname: Holmes
authors.forename: Suzanne
authors.initials: S
authors.lastname: Sherrill
authors.forename: Su-Jan
authors.initials: SJ
authors.lastname: Huang
authors.forename: Teresa
authors.initials: T
authors.lastname: Tolliver
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Lesch
authors.forename: Bai
authors.initials: B
authors.lastname: Lu
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Murphy
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D015306:Biogenic Monoamines / Q000378:metabolism*; D015153:Blotting, Western / Q000379:methods; D049628:Body Size / Q000235:genetics; D001921:Brain / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D001923:Brain Chemistry / Q000235:genetics; D019208:Brain-Derived Neurotrophic Factor / Q000172:deficiency* / Q000235:genetics; D002452:Cell Count; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004563:Electrochemistry / Q000379:methods; D005106:Exploratory Behavior / Q000502:physiology; D005786:Gene Expression Regulation / Q000235:genetics; D005838:Genotype; D018782:Maze Learning / Q000502:physiology; D008562:Membrane Glycoproteins / Q000172:deficiency* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000172:deficiency* / Q000235:genetics; D009474:Neurons / Q000166:cytology; D010147:Pain Measurement / Q000379:methods; D011863:Radioimmunoassay / Q000379:methods; D011897:Random Allocation; D011930:Reaction Time / Q000235:genetics; D050486:Serotonin Plasma Membrane Transport Proteins; D016622:Silver Staining / Q000379:methods; D013194:Staining and Labeling / Q000379:methods; D013312:Stress, Physiological / Q000378:metabolism*
chemical_list: D015306:Biogenic Monoamines; D019208:Brain-Derived Neurotrophic Factor; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050486:Serotonin Plasma Membrane Transport Proteins; C493231:Slc6a4 protein, mouse; D000324:Adrenocorticotropic Hormone