Experiment 1: Cocaine-induced locomotion in well habituated DAT/5-HT1B KO mice.

<p>Cocaine-induced locomotor activity in DAT/5-HT1B KO mice is expressed as absolute difference s from baseline, preinjection values. Post hoc analysis by 1 way ANOVA for COCAINE concentration revealed significant effects of cocaine for all genotypes except DAT −/−5-HT1B +/+ and DAT −/−5-HT1B −/−. Data are represented as mean ± SEM.</p

Experiment 3: The effects of the 5-HT antagonist SB 224289 on locomotor activity in DAT KO and WT mice.

<p>Time-course locomotor activity in DAT −/− and DAT +/+ mice after injection with 0, 5, 10, or 20 mg/kg SB 224289. Data are represented as mean ± the SEM.</p

Experiment 2: Locomotor activity in combined DAT/5-HT1B KO mice: short habituation sessions.

<p>(A) Time-course of locomotor activity during the first habituation session in DAT/5-HT1B KO mice (9 genotypes: DAT +/+5-HT1B +/+, DAT −/−5-HT1B +/+, DAT +/+5-HT1B −/−, DAT +/−5-HT1B −/−, DAT −/−5-HT1B +/−, DAT −/−5-HT1B −/−) expressed in terms of total distance traveled. (B) Cocaine-induced locomotor activity in DAT/5-HT1B KO mice expressed as absolute difference from saline (total activity after cocaine injection – total activity after saline injection). Data are represented as mean ± SEM.</p

Experiment 2: Time-course of locomotor activity in DAT/5-HT1B KO mice, short habituation sessions.

<p>Time-course of saline and cocaine-induced locomotor activity in DAT/5-HT1B KO mice, represented separately for each genotype. Cocaine increased locomotion in all DAT +/+ and DAT +/− genotypes (p<0.01), and reduced locomotion in all DAT −/− genotypes (p<0.01) except DAT −/−5-HT1B, which was confirmed by individual ANOVA comparing saline and cocaine locomotion for each genotype. Data are represented as mean ± SEM.</p

Experiment 1: Baseline locomotor activity in well habituated combined DAT/5-HT1B KO mice.

<p>Total locomotor activity in DAT/5-HT1B KO mice (9 genotypes: DAT +/+5-HT1B +/+, DAT −/−5-HT1B +/+, DAT +/+5-HT1B −/−, DAT +/−5-HT1B −/−, DAT −/−5-HT1B +/−, DAT −/−5-HT1B −/−) expressed in terms of summed distance traveled during all of the 4 habituation sessions prior to drug (5, 10 and 20 mg/kg IP cocaine; C5, C10 and C20 respectively) or saline (SAL) injections. *Significant difference from DAT +/+5-HT1B +/+ mice based on Scheffe’s post hoc comparison (p<0.05). Data are represented as mean ± SEM.</p

Experiment 1: Time-course of baseline locomotor activity in combined DAT/5-HT1B KO mice: long habituation session.

<p>Time-course of locomotor activity during the first habituation session in DAT/5-HT1B KO mice (9 genotypes: DAT +/+5-HT1B +/+, DAT −/−5-HT1B +/+, DAT +/+5-HT1B −/−, DAT +/−5-HT1B −/−, DAT −/−5-HT1B +/−, DAT −/−5-HT1B −/−) expressed in terms of total distance traveled. Data are represented as mean ± SEM.</p

Altered Reward Circuitry in the Norepinephrine Transporter Knockout Mouse

<div><p>Synaptic levels of the monoamine neurotransmitters dopamine, serotonin, and norepinephrine are modulated by their respective plasma membrane transporters, albeit with a few exceptions. Monoamine transporters remove monoamines from the synaptic cleft and thus influence the degree and duration of signaling. Abnormal concentrations of these neuronal transmitters are implicated in a number of neurological and psychiatric disorders, including addiction, depression, and attention deficit/hyperactivity disorder. This work concentrates on the norepinephrine transporter (NET), using a battery of <i>in vivo</i> magnetic resonance imaging techniques and histological correlates to probe the effects of genetic deletion of the norepinephrine transporter on brain metabolism, anatomy and functional connectivity. MRS recorded in the striatum of NET knockout mice indicated a lower concentration of NAA that correlates with histological observations of subtle dysmorphisms in the striatum and internal capsule. As with DAT and SERT knockout mice, we detected minimal structural alterations in NET knockout mice by tensor-based morphometric analysis. In contrast, longitudinal imaging after stereotaxic prefrontal cortical injection of manganese, an established neuronal circuitry tracer, revealed that the reward circuit in the NET knockout mouse is biased toward anterior portions of the brain. This is similar to previous results observed for the dopamine transporter (DAT) knockout mouse, but dissimilar from work with serotonin transporter (SERT) knockout mice where Mn²⁺ tracings extended to more posterior structures than in wildtype animals. These observations correlate with behavioral studies indicating that SERT knockout mice display anxiety-like phenotypes, while NET knockouts and to a lesser extent DAT knockout mice display antidepressant-like phenotypic features. Thus, the mainly anterior activity detected with manganese-enhanced MRI in the DAT and NET knockout mice is likely indicative of more robust connectivity in the frontal portion of the reward circuit of the DAT and NET knockout mice compared to the SERT knockout mice.</p> </div

Cocaine conditioned place preference among mice with different CSMD1 genotypes.

<p>Mean difference ± SEM in time spent on the cocaine-paired side (Y axis) before and after conditioning with different doses of cocaine for wildtype heterozygous and homozygote knockout mice (ANCOVA effect of genotype p = 0.024; n = 13–26 mice of each genotype for each dose). Data from male and female mice are combined since gender displayed no significant interaction with genotype.</p

Altered <i>CSMD1</i> Expression Alters Cocaine-Conditioned Place Preference: Mutual Support for a Complex Locus from Human and Mouse Models

<div><p>The CUB and sushi multiple domains 1 (<i>CSMD1</i>) gene harbors signals provided by clusters of nearby SNPs with 10^-2 > p > 10^-8 associations in genome wide association (GWAS) studies of addiction-related phenotypes. A <i>CSMD1</i> intron 3 SNP displays p < 10^-8 association with schizophrenia and more modest associations with individual differences in performance on tests of cognitive abilities. <i>CSDM1</i> encodes a cell adhesion molecule likely to influence development, connections and plasticity of brain circuits in which it is expressed. We tested association between <i>CSMD1</i> genotypes and expression of its mRNA in postmortem human brains (n = 181). Expression of <i>CSMD1</i> mRNA in human postmortem cerebral cortical samples differs 15–25%, in individuals with different alleles of simple sequence length and SNP polymorphisms located in the gene’s third/fifth introns, providing nominal though not Bonferroni-corrected significance. These data support mice with altered CSMD1 expression as models for common human CSMD1 allelic variation. We tested baseline and/or cocaine-evoked addiction, emotion, motor and memory-related behaviors in +/- and -/- <i>csmd1</i> knockout mice on mixed and on C57-backcrossed genetic backgrounds. Initial <i>csmd1</i> knockout mice on mixed genetic backgrounds displayed a variety of coat colors and sizable individual differences in responses during behavioral testing. Backcrossed mice displayed uniform black coat colors. Cocaine conditioned place preference testing revealed significant influences of genotype (p = 0.02). Homozygote knockouts displayed poorer performance on aspects of the Morris water maze task. They displayed increased locomotion in some, though not all, environments. The combined data thus support roles for common level-of-expression <i>CSMD1</i> variation in a drug reward phenotype relevant to addiction and in cognitive differences that might be relevant to schizophrenia. Mouse model results can complement data from human association findings of modest magnitude that identify likely polygenic influences.</p></div

Injection site locations are similar in wildtype and NET KO mice.

<p>Injection site locations, represented as a sphere for each animal of the 23 mice used in the statistical analysis of prefrontal cortex injections, confirms accurate placement for both groups (blue: wildtype littermates, red: NET KO). Injection site locations have been overlaid onto axial, transverse and sagittal semi-transparent rendered images of the MRI template (Scale bar  = 1 mm).</p