Neural correlates of script-driven imagery in adolescents with interpersonal traumatic experiences: A pilot study.

In adults, trauma imagery has proven to be a useful tool to assess the neural mechanisms of psychological trauma processing. In adolescents, heterogeneous results could be found for other tasks, however, a trauma imagery paradigm has not been evaluated. For this purpose, we investigated a trauma imagery paradigm with control scripts to assess neural correlates of traumatic experiences in youth. 15 adolescents, who had experienced a traumatic interpersonal event in the past and have developed clinically relevant symptoms, underwent an fMRI scan while listening to their individual trauma- versus two control scripts (positive/negative). We analysed a parametric contrast of the imagery phases (trauma > negative > positive) which revealed activity in the thalamus, dorsal anterior cingulate cortex, cuneus, dorsomedial prefrontal cortex and amygdala. Additionally, amygdala-activity correlated positively with depression-symptom-severity. Our data provide evidence for the feasibility of fMRI during a trauma imagery task in adolescents to investigate networks previously related to hyperarousal in adults with PTSD. Further, we demonstrate the specificity of the activated networks for trauma imagery as compared to imagery of other emotional situations. The task might be particularly useful to evaluate neural correlates of treatment in adolescents when hyperarousal is a target symptom.

Etomidate blocks LTP and impairs learning but does not enhance tonic inhibition in mice carrying the N265M point mutation in the beta3 subunit of the GABA(A) receptor.

Enhancement of tonic inhibition mediated by extrasynaptic α5-subunit containing GABAA receptors (GABAARs) has been proposed as the mechanism by which a variety of anesthetics, including the general anesthetic etomidate, impair learning and memory. Since α5 subunits preferentially partner with ß3 subunits, we tested the hypothesis that etomidate acts through ß3-subunit containing GABAARs to enhance tonic inhibition, block LTP, and impair memory. We measured the effects of etomidate in wild type mice and in mice carrying a point mutation in the GABAAR ß3-subunit (ß3-N265M) that renders these receptors insensitive to etomidate. Etomidate enhanced tonic inhibition in CA1 pyramidal cells of the hippocampus in wild type but not in mutant mice, demonstrating that tonic inhibition is mediated by ß3-subunit containing GABAARs. However, despite its inability to enhance tonic inhibition, etomidate did block LTP in brain slices from mutant mice as well as in those from wild type mice. Etomidate also impaired fear conditioning to context, with no differences between genotypes. In studies of recombinant receptors expressed in HEK293 cells, α5ß1γ2L GABAARs were insensitive to amnestic concentrations of etomidate (1 µM and below), whereas α5ß2γ2L and α5ß3γ2L GABAARs were enhanced. We conclude that etomidate enhances tonic inhibition in pyramidal cells through its action on α5ß3-containing GABAA receptors, but blocks LTP and impairs learning by other means - most likely by modulating α5ß2-containing GABAA receptors. The critical anesthetic targets underlying amnesia might include other forms of inhibition imposed on pyramidal neurons (e.g. slow phasic inhibition), or inhibitory processes on non-pyramidal cells (e.g. interneurons).

Distinct long-term neurocognitive outcomes after equipotent sevoflurane or isoflurane anaesthesia in immature rats.

BACKGROUND: Many anaesthetics when given to young animals cause cell death and learning deficits that persist until much later in life. Recent attempts to compare the relative safety or toxicity between different agents have not adequately controlled for the relative dose of anaesthetic given, thereby making direct comparisons difficult. METHODS: Isoflurane or sevoflurane were given at 1 minimum alveolar concentration (MAC) for 4 h to postnatal day 7 (P7) rat pups. Beginning at P75 these animals underwent fear conditioning and at P83 Morris water maze testing to assess working memory, short-term memory and early long-term memory using delays of 1 min, 1 h, and 4 h. RESULTS: No difference between groups was seen in fear conditioning experiments. Morris water maze learning was equivalent between groups, and no difference was seen in working memory. Sevoflurane-treated animals had a deficit in early long-term memory, and isoflurane-treated animals had a deficit in both short-term and early long-term memory. CONCLUSIONS: Both isoflurane and sevoflurane delivered at 1 MAC for 4 h to immature rats caused a deficit in long-term memory. Isoflurane also caused a deficit in short-term memory. Isoflurane might be more detrimental than sevoflurane in very young animals.

Inhaled anesthetic responses of recombinant receptors and knockin mice harboring α2(S270H/L277A) GABA(A) receptor subunits that are resistant to isoflurane.

The mechanism by which the inhaled anesthetic isoflurane produces amnesia and immobility is not understood. Isoflurane modulates GABA(A) receptors (GABA(A)-Rs) in a manner that makes them plausible targets. We asked whether GABA(A)-R α2 subunits contribute to a site of anesthetic action in vivo. Previous studies demonstrated that Ser270 in the second transmembrane domain is involved in the modulation of GABA(A)-Rs by volatile anesthetics and alcohol, either as a binding site or a critical allosteric residue. We engineered GABA(A)-Rs with two mutations in the α2 subunit, changing Ser270 to His and Leu277 to Ala. Recombinant receptors with these mutations demonstrated normal affinity for GABA, but substantially reduced responses to isoflurane. We then produced mutant (knockin) mice in which this mutated subunit replaced the wild-type α2 subunit. The adult mutant mice were overtly normal, although there was evidence of enhanced neonatal mortality and fear conditioning. Electrophysiological recordings from dentate granule neurons in brain slices confirmed the decreased actions of isoflurane on mutant receptors contributing to inhibitory synaptic currents. The loss of righting reflex EC(50) for isoflurane did not differ between genotypes, but time to regain the righting reflex was increased in N(2) generation knockins. This effect was not observed at the N(4) generation. Isoflurane produced immobility (as measured by tail clamp) and amnesia (as measured by fear conditioning) in both wild-type and mutant mice, and potencies (EC(50)) did not differ between the strains for these actions of isoflurane. Thus, immobility or amnesia does not require isoflurane potentiation of the α2 subunit.

[Interaction of Escherichia coli RNA polymerase with eukaryotic TATA-binding protein]. / Vzaimodeistvie RNK-polimerazy Escherichia coli s TATA-sviazyvaiushchim belkom éukariot.

Interaction with eukaryotic TATA-binding protein (TBP) was analyzed for natural Escherichia coli RNA polymerase or the recombinant holoenzyme, minimal enzyme, or its sigma subunit. Upon preincubation of full-sized RNA polymerase with TBP and further incubation with a constant amount of 32P-labeled phosphamide derivative of a TATA-containing oligodeoxyribonucleotide, the yield of the holoenzyme-oligonucleotide covalent complex decreased with increasing TBP concentration. This was considered as indirect evidence for complexing of RNA polymerase with TBP. In gel retardation assays, the holoenzyme, but neither minimal enzyme nor the sigma subunit, interacted with TPB, since the labeled probe formed complexes with both proteins in the reaction mixture combining TBP with the minimal enzyme or the sigma subunit. It was assumed that E. coli RNA polymerase is functionally similar to eukaryotic RNA polymerase II, and that the complete ensemble of all subunits is essential for the specific function of the holoenzyme.

Affinity labeling of RNA-polymerase II in the transcriptionally active complex by a phosphorylating analog of the initiation substrate.

Affinity modification of RNA-polymerase II by a phosphorylating analog of the initiation substrate carrying a zwitterionic 5;-terminal phosphate group with a 4-N,N-dimethylaminopyridine residue (DMAP-pA) was studied during specific transcription initiation controlled by the late adenoviral promotor. Super-selective affinity labeling and standard conditions of affinity modification resulted in labeling a polypeptide with molecular weight corresponding to that of the third subunit of the enzyme, RPB3 (45 kD). The initiation substrate (ATP) protects RNA-polymerase II from modification. The third subunit may be involved in the formation of the substrate-binding site of the enzyme.

Characterization of sensorimotor performance, reproductive and aggressive behaviors in segmental trisomic 16 (Ts65Dn) mice.

In the present study, segmental trisomy 16 (Ts65Dn) mice, an animal model of Down Syndrome (DS), were examined for sensorimotor, reproductive, and aggression abnormalities associated with DS. The Ts65Dn mice exhibited no sensorimotor deficits in olfactory sensitivity, visual abilities, orientation reactions, forelimb strength, postural skills, balance/ coordination, climbing, or locomotion compared to genetically matched control B6EiC3HF1 mice. In mating tests, the percentage of Ts65Dn mice displaying intromissions when paired with estrous females was significantly less than that in controls. Although the percentage of Ts65Dn mice that mounted and ejaculated with an estrous female was marginally less than in controls, there were no significant differences on the other measures of reproductive behavioral performance. In aggression tests, Ts65Dn males showed increased offensive aggression in a neutral arena both when paired and among grouped males. Conversely, Ts65Dn mice exhibited less offensive aggression against an intruder in their home cage than control males. In sum, these mice possess some of the adaptive behavior abnormalities observed in DS patients; however, because the Ts65Dn mice do not have any observed sensorimotor deficits that could interfere with behavioral assessments, they may serve as a useful model for the study of behavioral impairments associated with DS.

[The participation of transmembrane messenger systems in the action of steroid hormones on target cells]. / Uchastie transmembrannykh sistem posrednikov v deistvii steroidnykh gormonov na kletki-misheni.

Estradiol receptors are discovered in nuclei, cytoplasm and plasmatic membranes of the target cells. Estradiol activates the transmembrane polyphosphoinositide system: it stimulates the protein kinase C translocation from cytosol to cell membranes, the membrane protein phosphorylation being elevated. Transmembrane adenylate cyclase system is also activated. The cAMP system stimulation by estradiol is mediated by protein kinase C, phosphorylating a protein of adenylate cyclase complex. Estradiol causes protein kinases A translocation into the cell nuclei and enhances the protein kinase NII activity. The role of protein phosphorylation, activated by steroid hormones, in the transcription and protein synthesis regulation, is discussed.

[Mechanism of the stimulating effect of estradiol on protein kinase C in plasma membranes of target cells]. / Mekhanizmy stimuliruiushchego deistviia éstradiola na proteinkinazu C v plazmaticheskikh membranakh kletok-mishenei.

Using inhibitors and activators of protein kinase C, it was demonstrated that in isolated plasma membranes of target cells estradiol-17 beta selectively stimulates protein phosphorylation by endogenous protein kinase C. In estradiol-dependent tissues, estradiol effectuates the translocation of protein kinase C from the cytosol to the membrane fraction within 10-12 minutes. Estradiol activates protein kinase C in cellular membranes of target tissues via a mechanism which is different from that of phorbol ester (TPA): 3H-estradiol, in contrast with 3H-TPA, it is not bound by protein kinase C and, in contrast with TPA, estradiol-17 beta does not activate purified protein kinase C in vitro. In this case, the specific stimulation of protein kinase C translocation to membranes and the estradiol-induced increase in the phosphorylation of plasma membrane proteins seem to be due to the estradiol-induced activation of the transmembrane system of polyphosphoinositide degradation, eventually resulting in the formation of diacylglycerol, a protein kinase C activator.

[Translocation of protein kinase C from cytosol into cell membranes after treatment with estradiol and enzyme activation in target cells]. / Translokatsiia proteinkinazy C pod deistviem éstradiola iz tsitozolia v kletochnye membrany i aktivatsiia fermenta v kletkakh-misheniakh.

The effect of 17 beta-estradiol on protein kinase C in target cells was studied. It was shown that 10-15 min after injection of ovariectomized animals with estradiol (10 micrograms intraperitoneally) protein kinase C is translocated from the cytosol into the cell membranes of estradiol-dependent mammary gland tumours. A similar effect of estradiol on protein kinase C is observed in uterine tissue. On the contrast, in hormone-independent rat mammary gland tumours estradiol causes no redistribution of protein kinase C between the cytosol and cell membranes. No protein kinase C accumulation in the membranes of hormone-dependent mammary gland tumours is observed 30 min after estradiol injection. However, this period is characterized by the appearance of protein kinase whose activity is not stimulated by Ca2+ or phosphatidylserine and which is eluted from DEAE-cellulose with 0.2 M NaCl. This protein kinase presumably corresponds to the M-fragment, i.e., the catalytic part of protein kinase C formed as a result of protein kinase C proteolysis on the membranes. It seems likely that estradiol, similar to growth factor peptides, realizes its stimulating effect on cell division primarily at the expense of coupling of its membrane receptors with the protein kinase C activation system.