517 research outputs found
The brattleboro rat displays a natural deficit in social discrimination that is restored by clozapine and a neurotensin analog.
Cognitive deficits in schizophrenia are a major source of dysfunction for which more effective treatments are needed. The vasopressin-deficient Brattleboro (BRAT) rat has been shown to have several natural schizophrenia-like deficits, including impairments in prepulse inhibition and memory. We investigated BRAT rats and their parental strain, Long-Evans (LE) rats, in a social discrimination paradigm, which is an ethologically relevant animal test of cognitive deficits of schizophrenia based upon the natural preference of animals to investigate conspecifics. We also investigated the effects of the atypical antipsychotic, clozapine, and the putative antipsychotic, PD149163, a brain-penetrating neurotensin-1 agonist, on social discrimination in these rats. Adult rats were administered saline or one of the three doses of clozapine (0.1, 1.0, or 10 mg/kg) or PD149163 (0.1, 0.3, or 1.0 mg/kg), subcutaneously. Following drug administration, adult rats were exposed to a juvenile rat for a 4-min learning period. Animals were then housed individually for 30 min and then simultaneously exposed to the juvenile presented previously and a new juvenile for 4 min. Saline-treated LE rats, but not BRAT rats, exhibited intact social discrimination as evidenced by greater time spent exploring the new juvenile. The highest dose of clozapine and the two highest doses of PD149163 restored social discrimination in BRAT rats. These results provide further support for the utility of the BRAT rat as a genetic animal model relevant to schizophrenia and drug discovery. The potential of neurotensin agonists as putative treatments for cognitive deficits of schizophrenia was also supported
Photoionization in the time and frequency domain
Ultrafast processes in matter, such as the electron emission following light
absorption, can now be studied using ultrashort light pulses of attosecond
duration (s) in the extreme ultraviolet spectral range. The lack of
spectral resolution due to the use of short light pulses may raise serious
issues in the interpretation of the experimental results and the comparison
with detailed theoretical calculations. Here, we determine photoionization time
delays in neon atoms over a 40 eV energy range with an interferometric
technique combining high temporal and spectral resolution. We spectrally
disentangle direct ionization from ionization with shake up, where a second
electron is left in an excited state, thus obtaining excellent agreement with
theoretical calculations and thereby solving a puzzle raised by seven-year-old
measurements. Our experimental approach does not have conceptual limits,
allowing us to foresee, with the help of upcoming laser technology, ultra-high
resolution time-frequency studies from the visible to the x-ray range.Comment: 5 pages, 4 figure
Experimental Verification of the Chemical Sensitivity of Two-Site Double Core-Hole States Formed by an X-ray FEL
We have performed X-ray two-photon photoelectron spectroscopy (XTPPS) using
the Linac Coherent Light Source (LCLS) X-ray free-electron laser (FEL) in order
to study double core-hole (DCH) states of CO2, N2O and N2. The experiment
verifies the theory behind the chemical sensitivity of two-site (ts) DCH states
by comparing a set of small molecules with respect to the energy shift of the
tsDCH state and by extracting the relevant parameters from this shift.Comment: 11 pages, 2 figure
Cationic double K-hole pre-edge states of CS2 and SF6
Recent advances in X-ray instrumentation have made it possible to measure the
spectra of an essentially unexplored class of electronic states associated
with double inner-shell vacancies. Using the technique of single electron
spectroscopy, spectra of states in CS2 and SF6 with a double hole in the
K-shell and one electron exited to a normally unoccupied orbital have been
obtained. The spectra are interpreted with the aid of a high-level theoretical
model giving excellent agreement with the experiment. The results shed new
light on the important distinction between direct and conjugate shake-up in a
molecular context. In particular, systematic similarities and differences
between pre-edge states near single core holes investigated in X-ray
absorption spectra and the corresponding states near double core holes studied
here are brought out
Attosecond timing of electron emission from a molecular shape resonance
Shape resonances in physics and chemistry arise from the spatial confinement
of a particle by a potential barrier. In molecular photoionization, these
barriers prevent the electron from escaping instantaneously, so that nuclei may
move and modify the potential, thereby affecting the ionization process. By
using an attosecond two-color interferometric approach in combination with high
spectral resolution, we have captured the changes induced by the nuclear motion
on the centrifugal barrier that sustains the well-known shape resonance in
valence-ionized N. We show that despite the nuclear motion altering the
bond length by only , which leads to tiny changes in the potential
barrier, the corresponding change in the ionization time can be as large as
attoseconds. This result poses limits to the concept of instantaneous
electronic transitions in molecules, which is at the basis of the Franck-Condon
principle of molecular spectroscopy.Comment: 24 pages, 5 figure
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