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  • 1980-1984  (3)
  • Cerebral asymmetry  (2)
  • Freeze-fracture  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Asymmetrical effects of morphine and naloxone on reward mechanisms (1982)
    Springer
    Psychopharmacology 78 (1982), S. 219-224 
    Details
    ISSN: 1432-2072
    Keywords: Morphine ; Naloxone ; Cerebral asymmetry ; Self stimulation ; Rotation ; Reinforcement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats with bilaterally implanted lateral hypothalamic electrodes were tested daily for self-stimulation to each side of the brain, and rotation (circling behavior) was recorded concomitantly. All rats rotated in a preferred direction regardless of the side of the brain stimulated and all rats had asymmetries in self-stimulation sensitivity related to the direction of rotation. Morphine increased rotation and lowered self-stimulation thresholds at low doses (e.g., 2.5 mg/kg) and decreased rotation and raised self-stimulation thresholds at high doses (e.g., 20.0 mg/kg). The changes in self-stimulation thresholds preferentially occurred on opposite sides of the brain, i.e., the low-dose decrease in thresholds was greater in the normally less sensitive side of the brain whereas the high-dose increase in thresholds was greater in the normally more sensitive side of the brain. Naloxone produced no changes in rates of rotation but did elicit small changes in self-stimulation that varied with the side of the brain, i.e., dose-related decreases in thresholds occurred in the normally more sensitive side of the brain whereas dose-related increases in thresholds occurred in the normally less sensitive side of the brain. Subsequently rats were tested in a choice procedure providing concurrent access to rewarding stimulation of either side of the brain; currents were titrated such that, under baseline conditions, rats continually alternated between self-stimulating one side of the brain or the other. Morphine induced a preference for the less sensitive side of the brain that was comparable in magnitude at all doses and independent of its biphasic effects on rates of responding. Naloxone induced a dose-related preference for the more sensitive side of the brain while not altering rates of responding. Naloxone (1.0 mg/kg) also completely antagonized the effects of all doses of morphine. The results are discussed in terms of lateralized actions mediating the discriminable effects of reinforcing drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428154
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Amphetamine enhancement of reward asymmetry (1981)
    Springer
    Psychopharmacology 73 (1981), S. 323-327 
    Details
    ISSN: 1432-2072
    Keywords: Amphetamine ; Self-stimulation ; Cerebral asymmetry ; Rotation-Dopamine ; Schizophrenia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats with bilaterally implanted lateral hypothalamic electrodes were tested daily for self-stimulation to each side of the brain; rotation (circling behavior) was recorded concomitantly. All rats rotated in a perferred direction regardless of the side of the brain stimulated and all rats had asymmetries in self-stimulation sensitivity (threshold and rate-intensity functions) related to the direction of rotation. Amphetamine both enhanced rotation and potentiated the asymmetry in self-stimulation sensitivity. Subsequently rats were tested in a choice procedure providing concurrent access to rewarding stimulation of either side of the brain; currents were titrated such that, under baseline conditions, rats continually alternated between self-stimulating one side of the brain or the other. Amphetamine induced a robust preference for stimulation to the more sensitive side of the brain (the side having a lower thereshold). The results are discussed in relation to mechanisms of drug reinforcement and to biological etiologies of schizophrenia. It is proposed that schizophrenia results from a lateralized overactivity of dopaminergic neuronal systems mediating reward and that amphetamine mimics schizophrenic symptomatology by enhancing lateralization of the same systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00426459
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Lanthanum and freeze fracture studies on the retinular cell junction in the compound eye of the housefly (1981)
    Springer
    Cell & tissue research 214 (1981), S. 541-552 
    Details
    ISSN: 1432-0878
    Keywords: Lanthanum ; Freeze-fracture ; Housefly ; Photoreceptor cells ; Extracellular space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The retinular (R) cell junction between adjacent photoreceptor cells in the house-fly ommatidium was characterized by freeze fracture, thin section and tracer (lanthanum) studies. Focal tight junctions occur between cells, and some P face ridge-E face groove correspondences are present in this intramembranal area. When colloidal lanthanum was introduced into the extracellular space (ECS) of the peripheral retina of the housefly, this electrondense tracer moved from the ECS (extra-ommatidial space), through the R-cell junctions and belt desmosomes, into the ommatidial cavity (OC = intrarhabdomal space) of each ommatidium. In the OC, lanthanum outlined a meshwork structure that pervaded this space. The evidence of this tracer movement suggests that there may be ionic continuity between the “traditional” ECS and the fluid bathing the individual rhabdomeres. The volume of the OC is calculated and we suggest that this space is part of the ECS. The functional implications of this postulate are considered in the light of: (1) the different functions of the peripheral and central cells; (2) the dissimilarity of rhabdomal membrane surface facing the OC compared to the “unmodified” plasma membrane of the photoreceptor cell facing the extra-ommatidial cavity; (3) the permeability properties of the R cell junction; and (4) the total ECS containing an ion store capable of sustaining current for the generator potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233494
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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