Ketamine produces rapid and sustained antidepressant actions in depressed patients, but the precise cellular mechanisms underlying these effects have not been identified. Here we determined if ...modulation of neuronal activity in the infralimbic prefrontal cortex (IL-PFC) underlies the antidepressant and anxiolytic actions of ketamine. We found that neuronal inactivation of the IL-PFC completely blocked the antidepressant and anxiolytic effects of systemic ketamine in rodent models and that ketamine microinfusion into IL-PFC reproduced these behavioral actions of systemic ketamine. We also found that optogenetic stimulation of the IL-PFC produced rapid and long-lasting antidepressant and anxiolytic effects and that these effects are associated with increased number and function of spine synapses of layer V pyramidal neurons. The results demonstrate that ketamine infusions or optogenetic stimulation of IL-PFC are sufficient to produce long-lasting antidepressant behavioral and synaptic responses similar to the effects of systemic ketamine administration.
Stress is a complex human experience and having both rewarding and aversive motivational properties. The adverse effects of stress are well documented, yet many of underlying mechanisms remain ...unclear and controversial. Here we report that the anxiogenic properties of stress are encoded by the endogenous opioid peptide dynorphin acting in the basolateral amygdala. Using pharmacological and genetic approaches, we found that the anxiogenic-like effects of Corticotropin Releasing Factor (CRF) were triggered by CRF(1)-R activation of the dynorphin/kappa opioid receptor (KOR) system. Central CRF administration significantly reduced the percent open-arm time in the elevated plus maze (EPM). The reduction in open-arm time was blocked by pretreatment with the KOR antagonist norbinaltorphimine (norBNI), and was not evident in mice lacking the endogenous KOR ligand dynorphin. The CRF(1)-R agonist stressin 1 also significantly reduced open-arm time in the EPM, and this decrease was blocked by norBNI. In contrast, the selective CRF(2)-R agonist urocortin III did not affect open arm time, and mice lacking CRF(2)-R still showed an increase in anxiety-like behavior in response to CRF injection. However, CRF(2)-R knockout animals did not develop CRF conditioned place aversion, suggesting that CRF(1)-R activation may mediate anxiety and CRF(2)-R may encode aversion. Using a phosphoselective antibody (KORp) to identify sites of dynorphin action, we found that CRF increased KORp-immunoreactivity in the basolateral amygdala (BLA) of wildtype, but not in mice pretreated with the selective CRF(1)-R antagonist, antalarmin. Consistent with the concept that acute stress or CRF injection-induced anxiety was mediated by dynorphin release in the BLA, local injection of norBNI blocked the stress or CRF-induced increase in anxiety-like behavior; whereas norBNI injection in a nearby thalamic nucleus did not. The intersection of stress-induced CRF and the dynorphin/KOR system in the BLA was surprising, and these results suggest that CRF and dynorphin/KOR systems may coordinate stress-induced anxiety behaviors and aversive behaviors via different mechanisms.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Temporal control, or how organisms guide movements in time to achieve behavioral goals, depends on dopamine signaling. The medial prefrontal cortex controls many goal-directed behaviors and receives ...dopaminergic input primarily from the midbrain ventral tegmental area. However, this system has never been linked with temporal control. Here, we test the hypothesis that dopaminergic projections from the ventral tegmental area to the prefrontal cortex influence temporal control. Rodents were trained to perform a fixed-interval timing task with an interval of 20 s. We report several results: first, that decreasing dopaminergic neurotransmission using virally mediated RNA interference of tyrosine hydroxylase impaired temporal control, and second that pharmacological disruption of prefrontal D1 dopamine receptors, but not D2 dopamine receptors, impaired temporal control. We then used optogenetics to specifically and selectively manipulate prefrontal neurons expressing D1 dopamine receptors during fixed-interval timing performance. Selective inhibition of D1-expressing prefrontal neurons impaired fixed-interval timing, whereas stimulation made animals more efficient during task performance. These data provide evidence that ventral tegmental dopaminergic projections to the prefrontal cortex influence temporal control via D1 receptors. The results identify a critical circuit for temporal control of behavior that could serve as a target for the treatment of dopaminergic diseases.
Maladaptive responses to stress adversely affect human behavior, yet the signaling mechanisms underlying stress-responsive behaviors remain poorly understood. Using a conditional gene knockout ...approach, the α isoform of p38 mitogen-activated protein kinase (MAPK) was selectively inactivated by AAV1-Cre-recombinase infection in specific brain regions or by promoter-driven excision of p38α MAPK in serotonergic neurons (by
Slc6a4-Cre or
ePet1-Cre) or astrocytes (by
Gfap-CreERT2). Social defeat stress produced social avoidance (a model of depression-like behaviors) and reinstatement of cocaine preference (a measure of addiction risk) in wild-type mice, but not in mice having p38α MAPK selectively deleted in serotonin-producing neurons of the dorsal raphe nucleus. Stress-induced activation of p38α MAPK translocated the serotonin transporter to the plasma membrane and increased the rate of transmitter uptake at serotonergic nerve terminals. These findings suggest that stress initiates a cascade of molecular and cellular events in which p38α MAPK induces a hyposerotonergic state underlying depression-like and drug-seeking behaviors.
► p38α MAPK is for stress-induced behaviors including depression and addiction ► Selective p38α MAPK deletion in serotonergic neurons produces stress resilience ► p38α MAPK activation translocates the serotonin transporter ► Stress-induced dysphoria is caused by hyposerotoninergic tone
The nucleus of the solitary tract (NTS) is a key gateway for meal-related signals entering the brain from the periphery. However, the chemical mediators crucial to this process have not been fully ...elucidated. We reveal that a subset of NTS neurons containing cholecystokinin (CCK(NTS)) is responsive to nutritional state and that their activation reduces appetite and body weight in mice. Cell-specific anterograde tracing revealed that CCK(NTS) neurons provide a distinctive innervation of the paraventricular nucleus of the hypothalamus (PVH), with fibers and varicosities in close apposition to a subset of melanocortin-4 receptor (MC4R(PVH)) cells, which are also responsive to CCK. Optogenetic activation of CCK(NTS) axon terminals within the PVH reveal the satiating function of CCK(NTS) neurons to be mediated by a CCK(NTS)→PVH pathway that also encodes positive valence. These data identify the functional significance of CCK(NTS) neurons and reveal a sufficient and discrete NTS to hypothalamus circuit controlling appetite.
Although stress has profound effects on motivated behavior, the underlying mechanisms responsible are incompletely understood. In this study we elucidate a functional pathway in mouse brain that ...encodes the aversive effects of stress and mediates stress-induced reinstatement of cocaine place preference (CPP). Activation of the dynorphin/kappa opioid receptor (KOR) system by either repeated stress or agonist produces conditioned place aversion (CPA). Because KOR inhibition of dopamine release in the mesolimbic pathway has been proposed to mediate the dysphoria underlying this response, we tested dopamine-deficient mice in this study and found that KOR agonist in these mice still produced CPA. However, inactivation of serotonergic KORs by injection of the KOR antagonist norBNI into the dorsal raphe nucleus (DRN), blocked aversive responses to the KOR agonist U50,488 and blocked stress-induced reinstatement of CPP. KOR knockout (KO) mice did not develop CPA to U50,488; however, lentiviral re-expression of KOR in the DRN of KOR KO mice restored place aversion. In contrast, lentiviral expression in DRN of a mutated form of KOR that fails to activate p38 MAPK required for KOR-dependent aversion, did not restore place aversion. DRN serotonergic neurons project broadly throughout the brain, but the inactivation of KOR in the nucleus accumbens (NAc) coupled with viral re-expression in the DRN of KOR KO mice demonstrated that aversion was encoded by a DRN to NAc projection. These results suggest that the adverse effects of stress may converge on the serotonergic system and offers an approach to controlling stress-induced dysphoria and relapse.
Stress is a complex human experience having both positive and negative motivational properties. When chronic and uncontrollable, the adverse effects of stress on human health are considerable and yet ...poorly understood. Here, we report that the dysphoric properties of chronic stress are encoded by the endogenous opioid peptide dynorphin acting on specific stress-related neuronal circuits. Using different forms of stress presumed to evoke dysphoria in mice, we found that repeated forced swim and inescapable footshock both produced aversive behaviors that were blocked by a kappa-opioid receptor (KOR) antagonist and absent in mice lacking dynorphin. Injection of corticotropin-releasing factor (CRF) or urocortin III, key mediators of the stress response, produced place aversion that was also blocked by dynorphin gene deletion or KOR antagonism. CRF-induced place aversion was blocked by the CRF2 receptor antagonist antisauvigine-30, but not by the CRF1 receptor antagonist antalarmin. In contrast, place aversion induced by the KOR agonist U50,488 was not blocked by antisauvigine-30. These results suggest that the aversive effects of stress were mediated by CRF2 receptor stimulation of dynorphin release and subsequent KOR activation. Using a phospho-selective antibody directed against the activated KOR to image sites of dynorphin action in the brain, we found that stress and CRF each caused dynorphin-dependent KOR activation in the basolateral amygdala, nucleus accumbens, dorsal raphe, and hippocampus. The convergence of stress-induced aversive inputs on the dynorphin system was unexpected, implicates dynorphin as a key mediator of dysphoria, and emphasizes kappa-receptor antagonists as promising therapeutics.
Following repeated opioid use, some dependent individuals experience persistent cognitive deficits that contribute to relapse of drug-taking behaviors, and one component of this response may be ...mediated by the endogenous dynorphin/kappa opioid system in neocortex. In C57BL/6 male mice, we find that acute morphine withdrawal evokes dynorphin release in the medial prefrontal cortex (PFC) and disrupts cognitive function by activation of local kappa opioid receptors (KORs). Immunohistochemical analyses using a phospho-KOR antibody confirmed that both withdrawal-induced and optically evoked dynorphin release activated KOR in PFC. Using a genetically encoded sensor based on inert KOR (kLight1.2a), we revealed the in vivo dynamics of endogenous dynorphin release in the PFC. Local activation of KOR in PFC produced multi-phasic disruptions of memory processing in an operant-delayed alternation behavioral task, which manifest as reductions in response number and accuracy during early and late phases of an operant session. Local pretreatment in PFC with the selective KOR antagonist norbinaltorphimine (norBNI) blocked the disruptive effect of systemic KOR activation during both early and late phases of the session. The early, but not late phase disruption was blocked by viral excision of PFC KORs, suggesting an anatomically dissociable contribution of pre- and postsynaptic KORs. Naloxone-precipitated withdrawal in morphine-dependent mice or optical stimulation of pdyn
neurons using Channelrhodopsin-2 disrupted delayed alternation performance, and the dynorphin-induced effect was blocked by local norBNI. Our findings describe a mechanism for control of cortical function during opioid dependence and suggest that KOR antagonism could promote abstinence.
Neurotransmission and neuroinflammation are controlled by local increases in both extracellular ATP and the endocannabinoid 2-arachidonoyl glycerol (2-AG). While it is known that extracellular ATP ...stimulates 2-AG production in cells in culture, the dynamics and molecular mechanisms that underlie this response remain poorly understood. Detection of real-time changes in eCB levels with the genetically encoded sensor, GRAB
, can address this shortfall.
2-AG and arachidonoylethanolamide (AEA) levels in Neuro2a (N2a) cells were measured by LC-MS, and GRAB
fluorescence changes were detected using live-cell confocal microscopy and a 96-well fluorescence plate reader.
2-AG and AEA increased GRAB
fluorescence in N2a cells with EC
values of 81 and 58 nM, respectively; both responses were reduced by the cannabinoid receptor type 1 (CB
R) antagonist SR141617 and absent in cells expressing the mutant-GRAB
. ATP increased only 2-AG levels in N2a cells, as measured by LC-MS, and induced a transient increase in the GRAB
signal within minutes primarily via activation of P2X
receptors (P2X
R). This response was dependent on diacylglycerol lipase β activity, partially dependent on extracellular calcium and phospholipase C activity, but not controlled by the 2-AG hydrolysing enzyme, α/β-hydrolase domain containing 6 (ABHD6).
Considering that P2X
R activation increases 2-AG levels within minutes, our results show how these molecular components are mechanistically linked. The specific molecular components in these signalling systems represent potential therapeutic targets for the treatment of neurological diseases, such as chronic pain, that involve dysregulated neurotransmission and neuroinflammation.
Inactivation of opioid receptors limits the therapeutic efficacy of morphine-like analgesics and mediates the long duration of kappa opioid antidepressants by an uncharacterized, arrestin-independent ...mechanism. Here we use an iterative, discovery-based proteomic approach to show that following opioid administration, peroxiredoxin 6 (PRDX6) is recruited to the opioid receptor complex by c-Jun N-terminal kinase (JNK) phosphorylation. PRDX6 activation generates reactive oxygen species via NADPH oxidase, reducing the palmitoylation of receptor-associated Gαi in a JNK-dependent manner. Selective inhibition of PRDX6 blocks Gαi depalmitoylation, prevents the enhanced receptor G-protein association and blocks acute analgesic tolerance to morphine and kappa opioid receptor inactivation in vivo. Opioid stimulation of JNK also inactivates dopamine D2 receptors in a PRDX6-dependent manner. We show that the loss of this lipid modification distorts the receptor G-protein association, thereby preventing agonist-induced guanine nucleotide exchange. These findings establish JNK-dependent PRDX6 recruitment and oxidation-induced Gαi depalmitoylation as an additional mechanism of Gαi-G-protein-coupled receptor inactivation.Opioid receptors are important modulators of nociceptive pain. Here the authors show that opioid receptor activation recruits peroxiredoxin 6 (PRDX6) to the receptor-Gαi complex by c-Jun N-terminal kinase, resulting in Gαi depalmitoylation and enhanced receptor-Gαi association.
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