Search

Humans and many animals show 'freezing' behavior in response to threatening stimuli. In humans, inappropriate threat responses are fundamental characteristics of several mental illnesses. To identify small molecules that modulate threat responses, we developed a high-throughput behavioral assay in zebrafish (Danio rerio) and evaluated 10,000 compounds for their effects on freezing behavior. We found three classes of compounds that switch the threat response from freezing to escape-like behavior. We then screened these for binding activity across 45 candidate targets. Using target profile clustering, we identified the sigma-1 (σ1) receptor as having a role in the mechanism of behavioral switching and confirmed that known σ1ligands also disrupt freezing behavior. Furthermore, mutation of the gene encoding σ1prevented the behavioral effect of escape-inducing compounds. One compound, which we call finazine, potently bound mammalian σ1and altered threat-response behavior in mice. Thus, pharmacological and genetic interrogation of the freezing response revealed σ1as a mediator of threat responses in vertebrates.

Many psychiatric drugs act on multiple targets and therefore require screening assays that encompass a wide target space. With sufficiently rich phenotyping and a large sampling of compounds, it should be possible to identify compounds with desired mechanisms of action on the basis of behavioral profiles alone. Although zebrafish (Danio rerio) behavior has been used to rapidly identify neuroactive compounds, it is not clear what types of behavioral assays would be necessary to identify multitarget compounds such as antipsychotics. Here we developed a battery of behavioral assays in larval zebrafish to determine whether behavioral profiles can provide sufficient phenotypic resolution to identify and classify psychiatric drugs. Using the antipsychotic drug haloperidol as a test case, we found that behavioral profiles of haloperidol-treated zebrafish could be used to identify previously uncharacterized compounds with desired antipsychotic-like activities and multitarget mechanisms of action.

In clinical organ transplantation, donor and recipient age may differ substantially. Old donor organs accumulate senescent cells that have the capacity to induce senescence in naïve cells. We hypothesized that the engraftment of old organs may induce senescence in younger recipients, promoting age-related pathologies. When performing isogeneic cardiac transplants between age-mismatched C57BL/6old donor mice (18-months) and young and middle-aged C57BL/6recipients (3- or 12-months), we observed augmented frequencies of senescent cells in draining lymph nodes, adipose tissue, livers, and hindlimb muscles 30 days after transplantation. These observations went along with compromised physical performance and impaired spatial learning and memory abilities. Systemic levels of SASP factors including mitochondrial DNA (mt-DNA) were elevated in recipients. Of mechanistic relevance, injections of mt-DNA phenocopied effects of age-mismatched organ transplantation in accelerating aging. Single treatment of old donor animals with senolytics prior to transplantation attenuated mt-DNA release and improved physical capacities in young recipients.

Triple reuptake inhibitors (TRIs) that block the dopamine transporter (DAT), norepinephrine transporter, and serotonin transporter are being developed as a new class of antidepressant that may have better efficacy and fewer side effects compared with traditional antidepressants. We describe a novel TRI, 2-[4-(4-chlorophenyl)-1-methylpiperidin-3-ylmethylsulfanyl]-1-(3-methylpiperidin-1-yl)-ethanone (JZAD-IV-22), that inhibits all three monoamine transporters with approximately equal potency in vitro. (+/−)-1-(3,4-dichlorophenyl)-3-azabicyclo-[3.1.0]hexane hydrochloride (DOV 216,303), a TRI shown to be an effective antidepressant in a clinical trial, shows reuptake inhibition similar to that of JZAD-IV-22 in vitro. Furthermore, both JZAD-IV-22 and DOV 216,303 increase levels of dopamine, norepinephrine, and serotonin in the mouse prefrontal cortex when administered by peripheral injection. JZAD-IV-22 and DOV 216,303 exhibited antidepressant-like efficacy in the mouse forced-swim and tail-suspension tests at doses that increased neurotransmitter levels. Because development of DAT inhibitors could be hindered by abuse liability, both JZAD-IV-22 and DOV 216,303 were compared in two assays that are markers of abuse potential. Both JZAD-IV-22 and DOV 216,303 partially substituted for cocaine in a drug discrimination assay in rats, and high doses of DOV 216,303 produced locomotor sensitization in mice. JZAD-IV-22 showed no evidence of sensitization at any dose tested. These results demonstrate that JZAD-IV-22 is a TRI with antidepressant-like activity similar to that of DOV 216,303. The striking feature that distinguishes the two TRIs is that locomotor sensitization, a common underlying feature of drugs of abuse, is seen with DOV 216,303 but is completely lacking in JZAD-IV-22. These findings may have implications for the potential for abuse liability in humans.

Triple reuptake inhibitors (TRIs) that block the dopamine transporter (DAT), norepinephrine transporter, and serotonin transporter are being developed as a new class of antidepressant that may have better efficacy and fewer side effects compared with traditional antidepressants. We describe a novel TRI, 2-[4-(4-chlorophenyl)-1-methylpiperidin-3-ylmethylsulfanyl]-1-(3-methylpiperidin-1-yl)-ethanone (JZAD-IV-22), that inhibits all three monoamine transporters with approximately equal potency in vitro. (+/-)-1-(3,4-dichlorophenyl)-3-azabicyclo-[3.1.0]hexane hydrochloride (DOV 216,303), a TRI shown to be an effective antidepressant in a clinical trial, shows reuptake inhibition similar to that of JZAD-IV-22 in vitro. Furthermore, both JZAD-IV-22 and DOV 216,303 increase levels of dopamine, norepinephrine, and serotonin in the mouse prefrontal cortex when administered by peripheral injection. JZAD-IV-22 and DOV 216,303 exhibited antidepressant-like efficacy in the mouse forced-swim and tail-suspension tests at doses that increased neurotransmitter levels. Because development of DAT inhibitors could be hindered by abuse liability, both JZAD-IV-22 and DOV 216,303 were compared in two assays that are markers of abuse potential. Both JZAD-IV-22 and DOV 216,303 partially substituted for cocaine in a drug discrimination assay in rats, and high doses of DOV 216,303 produced locomotor sensitization in mice. JZAD-IV-22 showed no evidence of sensitization at any dose tested. These results demonstrate that JZAD-IV-22 is a TRI with antidepressant-like activity similar to that of DOV 216,303. The striking feature that distinguishes the two TRIs is that locomotor sensitization, a common underlying feature of drugs of abuse, is seen with DOV 216,303 but is completely lacking in JZAD-IV-22. These findings may have implications for the potential for abuse liability in humans.

Nicotine has been shown to have effects on anxiety and depression in both human and animal studies. These studies suggest that nicotinic acetylcholine receptors (nAChRs) can modulate the function of pathways involved in stress response, anxiety and depression in the normal brain, and that smoking can result in alterations of anxiety level and mood. The effects of nicotine are complex however, and nicotine treatment can be either anxiolytic or anxiogenic depending on the anxiety model tested, the route of nicotine administration and the time course of administration. The paradoxical effects of nicotine on emotionality are likely due to the broad expression of nAChRs throughout the brain, the large number of nAChR subtypes that have been identified and the ability of nicotine treatment to both activate and desensitize nAChRs. Activation of nAChRs has been shown to modulate many systems associated with stress response including stress hormone pathways, monoaminergic transmission and release of classical neurotransmitters throughout the brain. Local administration studies in animals have identified brain areas that may be involved in the anxiogenic and anxiolytic actions of nicotine including the lateral septum, the dorsal raphe nuclei, the mesolimbic dopamine system and the hippocampus. The ensemble of studies to date suggest that under certain conditions nicotine can act as an anxiolytic and an antidepressant, but that following chronic use, adaptations to nicotine can occur resulting in increased anxiety and depression following withdrawal.

The reinforcing properties of nicotine and psychomotor stimulants are thought to be mediated through the mesolimbic dopamine (DA) system. This study investigates the role of high affinity nicotinic acetylcholine receptors (nAChRs) in cocaine place preference and examines some neurochemical changes in the mesolimbic DA system that might account for the interaction between nicotine and cocaine. 5 mg/kg is the lowest dose of cocaine able to condition a place preference in C57Bl/6 mice. Co-treatment with the nicotinic antagonist mecamylamine (1.0 mg/kg) disrupted place preference to 5 mg/kg cocaine. In addition, mice lacking the high affinity nAChR containing the β2 subunit showed decreased place preference to 5 mg/kg cocaine, although higher doses of cocaine could condition a place preference in these knock out animals. In contrast, co-administration of a low dose of nicotine (0.2 mg/kg) potentiated place preference to a subthreshold dose of cocaine (3 mg/kg). DA turnover was monitored in several brain regions using tissue levels of DA and its primary metabolite DOPAC as an indication of DA release. Wild type mice showed decreased DA turnover following treatment with 5 mg/kg cocaine; whereas, this response was not seen in mice lacking the β2 subunit of the nAChR. Induction of chronic fos-related antigens by cocaine was also reduced in mutant mice as compared to their wild type siblings, implying that downstream actions of cocaine were also affected by inactivation of the high affinity nAChR. These data indicate that activation of the high affinity nAChR may contribute to cocaine reinforcement.

Molecular cloning has elucidated the sequence of a family of acetylcholine receptor subunits that are activated by nicotine. Subsequent studies on the localization of individual subunits and the physiological properties of nicotinic subunit combinations in vitro, have led to identification of subunit compositions of nicotinic receptors that may function in vivo, as the native receptor. A particular challenge for the field has been to use these molecular data to determine which individual nicotinic receptor subtype is responsible for mediating each of the behavioral effects of nicotine. Human and animal studies have shown that nicotine is reinforcing and likely responsible for the addictive properties of tobacco. In addition, nicotine has been shown to have effects on locomotion, cognition, affect, and pain sensitivity. Recent studies combining the techniques of molecular biology, pharmacology, electrophysiology, and behavioral analysis to analyze knock out mice that lack individual subunits of the nicotinic acetylcholine receptor, have helped identify the role of specific nicotinic subunits in some of these complex behaviors. These studies could ultimately be useful in designing specific nicotinic receptor agonists and antagonists that may have uses in the clinic.

AbstractAs a natural extension of a preceding work on the vibrational linewidths in two isomorphic 1,4-dihalobenzenes crystals (DBB and BCB, which is orientationally disordered), calculations of the anharmonic contribution to the linewidths have been performed. The calculations show that the decay mechanisms that were previously postulated are compatible with the inter-molecular potential. Some corrections to previous results are illustrated. The disorder contribution to the linewidth and its dependence on the relaxing mode are briefly discussed.

Reducing brain blood flow induces toxic but druggable cis P-tau that drives progressive neurodegeneration and memory loss in mice.

In an extensive backcross of mice between C3H/HeJ (C3H) and C57BL/6J (B6), we sought to map genes that influence learning and memory as measured by performance in a contextual fear-conditioning paradigm. Our results indicate that there are several genetic regions that have a strong influence on performance in this paradigm. The strongest influences map to the proximal and distal ends of chromosome 1 (lod scores of 5.14 and 4.76, respectively). Other chromosomal regions (chromosomes 3, 7, 8, 9 and 18) were also identified as candidates for regions containing genes influencing contextual fear conditioning, with lod scores ranging from 1.8 to 2.7.

C3 deficiency protects against hippocampal neurodegeneration and cognitive decline in aged APP/PS1 mice despite abundant Aβ plaques.