Ketamine exerts fast acting, robust, and lasting antidepressant effects in a sub-anesthetic dose, however, the underlying mechanisms are still not fully elucidated. Recent studies have suggested that ketamine's antidepressant effects are probably attributed to the activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. The present study aimed to observe the effects of AMPA receptor modulators on mammalian target of rapamycin (mTOR) and brain-derived neurotrophic factor (BDNF) expression during the procedure of ketamine exerting antidepressant effects. Therefore, we pretreated rats with NBQX, an AMPA receptor antagonist, or CX546, an AMPA receptor agonist, and subsequently observed the immobility time during the forced swimming test (FST) and the hippocampal and prefrontal cortical levels of mTOR and BDNF. The results showed ketamine decreased the immobility time of rats during the FST and increased the hippocampal and prefrontal cortical mTOR and BDNF. NBQX pretreatment significantly increased the immobility time and decreased the levels of mTOR and BDNF when compared with vehicle 1 (DMSO) pretreatment. CX546 pretreatment significantly decreased the immobility time and increased the levels of mTOR and BDNF when compared with vehicle 2 (DMSO+ethanol) pretreatment. Our results suggest ketamine-induced antidepressant effects are associated with AMPA receptors-mediated upregulation of mTOR and BDNF in rat hippocampus and prefrontal cortex.

Persistent relapse to addictive drugs constitutes the most challenging problem in addiction therapy, and is linked to impaired prefrontal cortex regulation of motivated behaviors involving the nucleus accumbens. Using a rat model of heroin addiction, we show that relapse requires long-term potentiation (LTP)-like increases in synaptic strength in the prefrontal cortex projection to the nucleus accumbens. The increased synaptic strength was paralleled by dendritic spine enlargement in accumbens spiny neurons and required up-regulated surface expression of NMDA2b-containing receptors (NR2B). Accordingly, blocking NR2B before reinstating heroin-seeking prevented the induction of LTP-like changes in spine remodeling and synaptic strength, and inhibited heroin relapse. These data show that LTP-like neuroplasticity in prefrontal-accumbens synapses is initiated by NR2B stimulation and strongly contributes to heroin relapse. Moreover, the data reveal NR2B-containing NMDA receptors as a previously unexplored therapeutic target for treating heroin addiction.glutamate | field excitatory postsynaptic potential | diolistic neuron labeling | whole-cell recording | self-administration D rug addiction is characterized by an enduring vulnerability to relapse, and the propensity to relapse has been linked to cognitive impairments in the prefrontal cortex (PFc) (1, 2). Relapse requires memory recall, and akin to other forms of memory processing, relapse relies on synaptic plasticity. The glutamatergic projection from the PFc to the nucleus accumbens (NAc) undergoes long-lasting neuroplasticity following chronic cocaine administration (3-5), including long-term increases in the strength of excitatory synapses on medium spiny neurons (MSNs) in the NAc following chronic cocaine administration (4, 6, 7). Synaptic potentiation is indicated in studies showing increased AMPA relative to NMDA currents in vitro (7), increased field potentials in prefrontal to accumbens synapses in vivo (6), elevated surface expression of the accumbens AMPA glutamate GluR1 receptor subunit (4), and increased density and diameter of dendritic spines on accumbens MSNs (8, 9). Based on these findings, it has been proposed that pathologies in the PFc to NAc synapses may contain novel pharmacotherapeutic targets for treating addiction (3, 4).Although chronic cocaine administration alters basal excitatory transmission in PFc synapses on accumbens MSNs, understanding of the role played by drug-induced neuroplasticity in relapse is incomplete and may even be misleading because all studies to date examine neuroplasticity produced after a withdrawal period and do not measure the synaptic plasticity initiated by a relapse episode (5, 10). Another potential limitation in our current understanding is that although the PFc projections to NAc are likely involved in relapse to most drugs of abuse (11), the current perception that addiction is associated with synaptic potentiation in the NAc is derived largely from experiments with chronic cocaine administration (12). An in...

Cocaine addiction remains without an effective pharmacotherapy and is characterized by an inability of addicts to inhibit relapse to drug use. Vulnerability to relapse arises from an enduring impairment in cognitive control of motivated behavior, manifested in part by dysregulated synaptic potentiation and extracellular glutamate homeostasis in the projection from the prefrontal cortex to the nucleus accumbens. Here we show in rats trained to self-administer cocaine that the enduring cocaine-induced changes in synaptic potentiation and glutamate homeostasis are mechanistically linked through group II metabotropic glutamate receptor signaling. The enduring cocaine-induced changes in measures of cortico-accumbens synaptic and glial transmission were restored to predrug parameters for at least 2 wk after discontinuing chronic treatment with the cystine prodrug, N-acetylcysteine. N-acetylcysteine produced these changes by inducing an enduring restoration of nonsynaptic glutamatergic tone onto metabotropic glutamate receptors. The long-lasting pharmacological restoration of cocaine-induced glutamatergic adaptations by chronic N-acetylcysteine also caused enduring inhibition of cocaine-seeking in an animal model of relapse. These data mechanistically link nonsynaptic glutamate to cocaineinduced adaptations in excitatory transmission and demonstrate a mechanism to chronically restore prefrontal to accumbens transmission and thereby inhibit relapse in an animal model. C ocaine addiction remains without an effective pharmacotherapy and is characterized by an inability of addicts to inhibit relapse to drug use. An enduring cocaine-induced impairment in cognitive control of motivated behavior contributes to the vulnerability to relapse (1, 2). Projections from the frontal cortex to the basal ganglia constitute a primary brain substrate for regulating motivated behavior (3). Cocaine-induced neuropathologies in the projection from the prefrontal cortex to the nucleus accumbens are implicated in cocaine addiction (4), including impaired neuroplasticity and synaptic communication (4,5). For example, prefrontal synapses in the accumbens undergo enduring potentiation (6-9), and the ability of these synapses to increase or decrease synaptic strength is impaired (7, 10). In addition, withdrawal from chronic cocaine use increases both presynaptic release estimated by elevated frequency of miniature excitatory postsynaptic currents (mEPSC) and by postsynaptic strength measured as increases in the surface expression of AMPA glutamate receptors and the ratio of AMPA/NMDA currents at glutamatergic synapses (6,8,11).Neuroimaging in cocaine addicts reveals reduced activity in prefrontal cortex under baseline conditions, but marked hyperresponsiveness in the prefrontal cortex and accumbens that is correlated with a desire for drug upon exposure to drug-associated stimuli (12). Similarly, animal models of relapse show that activation of this pathway is necessary and sufficient to reinstate cocaine-seeking behavior (13) and that neuronal ac...

Although polymerase chain reaction (PCR) is the most widely used method for DNA amplification, the requirement of thermocycling limits its non-laboratory applications. Isothermal DNA amplification techniques are hence valuable for on-site diagnostic applications in place of traditional PCR. Here we describe a true isothermal approach for amplifying and detecting double-stranded DNA based on a CRISPR–Cas9-triggered nicking endonuclease-mediated Strand Displacement Amplification method (namely CRISDA). CRISDA takes advantage of the high sensitivity/specificity and unique conformational rearrangements of CRISPR effectors in recognizing the target DNA. In combination with a peptide nucleic acid (PNA) invasion-mediated endpoint measurement, the method exhibits attomolar sensitivity and single-nucleotide specificity in detection of various DNA targets under a complex sample background. Additionally, by integrating the technique with a Cas9-mediated target enrichment approach, CRISDA exhibits sub-attomolar sensitivity. In summary, CRISDA is a powerful isothermal tool for ultrasensitive and specific detection of nucleic acids in point-of-care diagnostics and field analyses.