There are large individual differences among humans and animals in behavioral, physiological and toxicological responses to drugs of abuse. Many of these individual differences in behavioral responses to drugs display substantial genetic components. Transgenic animals provide means for approaching several interrelated goals: 1)Ascertainment of biochemical and behavioral consequences of the introduction of or disruption of specific genes;2)Ascertainment of the consequences of over- or under-expressing candidate genes identified in human studies;3) Elucidation of gene elements yielding cell-type specific expression and trans-synaptic gene regulation;4) Studying influences of interactions between variants at different genomic loci;5)Elucidating haplotype-specific levels of expression differences in vivo, and 6) allowing us to monitor synaptic connectivities and their modulation by drug administration and alterations in haplotypes in cell adhesion and other impoprtant brain molecules. Interest mechanisms of reward, reinforcement and learning have led to continuing focus on these systems during this year, as we have established much of the groundwork for identification of wiring differences in brain slices. In continuing studies of combined transporter and transporter/receptor knockouts, we have reported novel data concerning the differential influences of these knockouts on a) conditioned locomotion associated with cocaine and b) aversive properties associated with drugs of abuse, as monitored using conditioned taste aversions. In studies of variations at candidate gene loci determined from studies of drug-regulated gene expression, we have reported subtle alterations in long term drug effects in mice that we have produced with altered levels of expression of KEPI. These mice also provide an opportunity to provide a technical advance, demonstrating marker-assisted selection for recombinants between the knockout locus and a nearby QTL. We have characterized alterations in leucine-suppressed food intake in mice that we have produced with deletions of an orphan transporter v7-3 and identified its role in uptake of proline and leucine in brain synaptosomes, as well as the ability of other uptake systems to compensate for any effects of its constutuitive deletion on a variety of behaviors. In other single gene knockout experiments, we have reported effects of transporter and receptor deletions on reward and depression related phenotypes. We have initiated studies of the influences of cell adhesion gene alterations by piloting multiphoton microscopic evaluation of fluorescence in eYFP/thy mice that are being bred with CAM KOs. We have reported or completetd use of imaging techniques to seek normal or altered volumetric, diffusion tensor imaging and Mn++ enhanced tract tracing evaluation in several strains of transporter and cell adhesion molecules, in collaboration with R Jacobs, Caltech.
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