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  • 1
    ISSN: 1432-1106
    Keywords: Key words Opioids ; µ-Receptors ; κ-Receptors ; Aversion ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We studied the effects of morphine injected either systemically or into the dorsal periaqueductal gray (DPAG) or nucleus accumbens (NA) using conventional and ethological analyses of behavior of rats submitted to the elevated plus-maze test with transparent walls. Intraperitoneal morphine (0.1 mg/kg and 0.3 mg/kg) increased both standard and ethological measures, expressing general exploratory activity such as total arm entries, end-exploration, scanning, head-dipping, and rearing. Morphine 10 (7.6 µg/µl) and 30 nmol (23 µg/µl) injected into nucleus accumbens produced similar effects, which were blocked by i.p. naltrexone (2.0 mg/kg), an opioid antagonist with good affinity for µ-opioid receptors. Morphine injected into the DPAG produced either antiaversive (10 nmol) or aversive effects (30 nmol), which respectively reduced and increased entries and time spent in the open arms and behaviors associated with risk assessment (peeping out, stretched attend postures, and flat back approach). The proaversive effects were inhibited by i.p. norbinaltorphimine (2.0 mg/kg), a selective inhibitor for κ-opioid receptors. These findings support the contention that at least some of the motivational effects of morphine may be due to activation of opioid mechanisms in nucleus accumbens, and DPAG has neural substrates for antiaversive and aversive effects of morphine. Moreover, on the basis of previous and present data obtained in this laboratory, it is suggested that stimulation of µ-opioid receptors inhibits and stimulation of κ-receptors activates the neural substrate of aversion in the DPAG. On the other hand, the increase in exploratory behavior due to interaction of morphine with µ-opioid receptors in the nucleus accumbens may be due to the stimulation of the interface between neural substrates of motivation and motor output in this structure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2754-2756 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new concept of electronic deexcitation of defects has been developed for systems where the electron couples very strongly with a local lattice mode. The model is based on a classical-quantum description of the configuration curve diagram and proposes that an electronic transition may be induced when the wave packets of the lattice oscillators in the upper and lower states involved overlap. It was successfully applied to the F-center system, at low temperature, in almost all the alkali halides. The luminescence efficiency derived from the model explains very well the observations, even the fact that the F* electron always reaches the relaxed excited state.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5044-5047 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal diffusivity results for superconducting YBa2Cu3O7−x systems are reported. Two laser excitation techniques were used: photoacoustic phase-lag and the flash method. We observed an anomalous jump in the thermal diffusivity at the critical temperature and related it to the electronic specific heat anomaly. This correlation yielded a characteristic phonon frequency of 320 cm−1 in the range of an active Raman mode already observed in a single crystal of the same compound. This result reinforces the current electron-phonon coupling mechanism as responsible for superconductivity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2072
    Keywords: 5-HT1A receptors ; 5-HT2 receptors ; Anxiety ; Gepirone ; Ketanserin ; Plus-maze test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Acute administration of gepirone, a 5-HT1A agonist, caused a dose dependent (1–10 mg/kg, IP) reduction in the locomotor activity (open and closed arms) of rats tested in the elevated plus-maze. However, rats housed in individual cages and submitted to chronic treatment with gepirone (10 mg/kg PO) showed a marked increase in the percentages of number and time spent in the open arms as compared to controls. These results are compatible with the idea that the antiaversive effect due to long-term treatment with 5-HT1A agonists is the result of a progressive desensitization of the somatodendritic 5-HT autoreceptor with the consequent recovery of firing rate of 5-HT neurons along with an activation of normosensitive postsynaptic 5-HT neurons. Ketanserin caused a biphasic effects on the exploratory behavior of rats in the plus-maze. The lower dose (0.5 mg/kg) decreased the aversion to the open arms and the higher dose (1.0 mg/kg) caused an unspecific decrease in the overall activity of the animals. Ketanserin is supposed to have antagonistic action on 5-HT2 and on α-adrenergic receptors. As prazosin (0.5–1.0 mg/kg), an α-adrenergic receptor blocker, did not present any significant effect in the present work it is suggested that the effects of the lower dose of ketanserin was due to its high antagonistic action on 5-HT2 receptors.
    Type of Medium: Electronic Resource
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