Recombinant Adeno-Associated Virus-mediated rescue of function in a mouse model of Dopamine Transporter Deficiency Syndrome.

Dopamine Transporter Deficiency Syndrome (DTDS) is a rare autosomal recessive disorder caused by loss-of-function mutations in dopamine transporter (DAT) gene, leading to severe neurological disabilities in children and adults. DAT-Knockout (DAT-KO) mouse is currently the best animal model for this syndrome, displaying functional hyperdopaminergia and neurodegenerative phenotype leading to premature death in ~36% of the population. We used DAT-KO mouse as model for DTDS to explore the potential utility of a novel combinatorial adeno-associated viral (AAV) gene therapy by expressing DAT selectively in DA neurons and terminals, resulting in the rescue of aberrant striatal DA dynamics, reversal of characteristic phenotypic and behavioral abnormalities, and prevention of premature death. These data indicate the efficacy of a new combinatorial gene therapy aimed at rescuing DA function and related phenotype in a mouse model that best approximates DAT deficiency found in DTDS.

Aversive stimulus differentially triggers subsecond dopamine release in reward regions.

Aversive stimuli have a powerful impact on behavior and are considered to be the opposite valence of pleasure. Recent studies have determined some populations of ventral tegmental area (VTA) dopaminergic neurons are activated by several types of aversive stimuli, whereas other distinct populations are either inhibited or unresponsive. However, it is not clear where these aversion-responsive neurons project, and whether alterations in their activity translate into dopamine release in the terminal field. Here we show unequivocally that the neurochemical and anatomical substrates responsible for the perception and processing of pleasurable stimuli within the striatum are also activated by tail pinch, a classical painful and aversive stimulus. Dopamine release is triggered in the dorsal striatum and nucleus accumbens (NAc) core by tail pinch and is time locked to the duration of the stimulus, indicating that the dorsal striatum and NAc core are neural substrates, which are involved in the perception of aversive stimuli. However, dopamine is released in the NAc shell only when tail pinch is removed, indicating that the alleviation of aversive condition could be perceived as a rewarding event.

Long-term deficiency of circulating and hippocampal insulin-like growth factor I induces depressive behavior in adult mice: a potential model of geriatric depression.

Numerous studies support the hypothesis that deficiency of insulin-like growth factor I (IGF-1) in adults contributes to depression, but direct evidence is limited. Many psychological and pro-cognitive effects have been attributed to IGF-1, but appropriate animal models of adult-onset IGF-1 deficiency are lacking. In this study, we use a viral-mediated Cre-loxP system to knockout the Igf1 gene in either the liver, neurons of the CA1 region of the hippocampus, or both. Knockout of liver Igf1 reduced serum IGF-1 levels by 40% and hippocampal IGF-1 levels by 26%. Knockout of Igf1 in CA1 reduced hippocampal IGF-1 levels by 13%. The most severe reduction in hippocampal IGF-1 occurred in the group with knockouts in both liver and CA1 (36% reduction), and was associated with a 3.5-fold increase in immobility in the forced swim test. Reduction of either circulating or hippocampal IGF-1 levels did not alter anxiety measured in an open field and elevated plus maze, nor locomotion in the open field. Furthermore, local compensation for deficiencies in circulating IGF-1 did not occur in the hippocampus, nor were serum levels of IGF-1 upregulated in response to the moderate decline of hippocampal IGF-1 caused by the knockouts in CA1. We conclude that adult-onset IGF-1 deficiency alone is sufficient to induce a depressive phenotype in mice. Furthermore, our results suggest that individuals with low brain levels of IGF-1 are at increased risk for depression and these behavioral effects are not ameliorated by increased local IGF-1 production or transport. Our study supports the hypothesis that the natural IGF-1 decline in aging humans may contribute to geriatric depression.

NRP/B mutations impair Nrf2-dependent NQO1 induction in human primary brain tumors.

Brain tumors are associated with genetic alterations of oncogenes and tumor suppressor genes. Accumulation of reactive oxygen species (ROS) in cells leads to oxidative stress-induced damage, resulting in tumorigenesis. Here, we showed that the nuclear matrix protein nuclear restricted protein in brain (NRP/B) was colocalized and interacted with NF-E2-related factor 2 (Nrf2). During oxidative stress response, NRP/B expression and its interaction with Nrf2 were upregulated in SH-SY5Y cells. Association of NRP/B with Nrf2 was crucial for NAD(P)H:quinone oxidoreductase 1 (NQO1) expression. NRP/B was localized predominantly in the nucleus of normal brain cells, whereas in primary brain tumors NRP/B was almost exclusively contained in the cytoplasm. In addition, unlike wild-type NRP/B, the expression of NRP/B mutants isolated from primary brain tumors was found in the cytoplasm, and these mutants failed to induce Nrf2-dependent NQO1 transcription. Thus, NRP/B mutations and their altered localization resulted in changes in NRP/B function and deregulation of Nrf2-dependent NQO1 activation in brain tumors. This study provides insights into the mechanism by which the NRP/B modulates Nrf2-dependent NQO1 induction in cellular protection against ROS in brain tumors.

Time course for the induction and maintenance of tolerance to Delta(9)-tetrahydrocannabinol in mice.

The time course for the development of tolerance to delta-9-tetrahydrocannabinol (Delta(9)-THC) was studied in an effort to determine the role that length of dosing may have in the onset and maintenance of tolerance. Mice were chronically treated with either vehicle or 10 mg/kg of Delta(9)-THC subcutaneously twice a day. The mice were tested 24 h after the last injection for tolerance as assessed by the production of antinociception and suppression of spontaneous activity. Tolerance was first observed after three injections of Delta(9)-THC (1.5 days) resulting in a 7-fold and 23-fold decrease in potency for the measures of antinociception and hypoactivity, respectively. Seven injections of Delta(9)-THC (3.5 days of dosing) resulted in a 12-fold and 36-fold decrease in potency, respectively, while 13 injections of Delta(9)-THC (6.5 days of dosing) produced a 6.2-fold and 9.8-fold degree of tolerance. The time course for the recovery from Delta(9)-THC-induced tolerance was also determined with a separate group of animals. Mice were dosed for 6.5 days with 10 mg/kg of Delta(9)-THC and were not tested until 4.5, 7.5, and 11.5 days after cessation of drug treatment. After 4.5 days without drug treatment the mice exhibited a 7.5-fold and 2.3-fold degree of tolerance as measured by antinociception and hypoactivity, respectively. After 7. 5 days without drug treatment a 3.4-fold degree of tolerance remained for the measure of antinociception, while no tolerance was detected for the measure of hypoactivity. No tolerance was observed for the measure of antinociception after 11.5 days without drug treatment. This time course indicates that the mechanisms responsible for either the production or maintenance of tolerance differ between the measures of antinociception and suppression of spontaneous activity.

Nicotine-induced acute tolerance: studies involving schedule-controlled behavior.

The major goal of the present study was to examine acute tolerance to nicotine-induced disruption of operant behavior following a single, noncontingent injection. Rats were trained to lever press for food reinforcement under a fixed ratio-30 schedule. Once trained, rats were injected with either saline or nicotine (0.8 mg/kg) in their home cages. After either a 90- or 180-min delay, each rat was injected with nicotine (0.4 mg/kg) and placed in the operant chamber for a 30-min behavioral evaluation session. This experiment was replicated with slight modifications 1 week later. The results of the present study suggest that 0.8 mg/kg of nicotine produces acute tolerance to the response rate decreasing effects of 0.4 mg/kg of nicotine. Because the tolerance-producing dose of nicotine was injected while rats were not in the test environment, they did not have an opportunity to practice the target behavior while under the influence of the drug. Hence, the acute tolerance observed in this study appears to be, at least partly, pharmacological (vs. behavioral) in nature, and may be related to a desensitization of central nicotinic acetylcholinergic receptors (nAChRs).