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  • 1
    Electronic Resource
    Electronic Resource
    Amphetamine Promotes Neostriatal Ascorbate Release via a Nigro-Thalamo-Cortico-Neostriatal Loop (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 63 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In the neostriatum, amphetamine and other dopamine agonists elevate the extracellular level of ascorbate, which is known to modulate neostriatal function. Although both D1 and D2 receptors have been linked to neostriatal ascorbate release, ample evidence suggests it is controlled by areas outside the neostriatum. The present series of experiments used selective lesions and intracerebral drug infusions to probe the involvement of the ventromedial thalamus and substantia nigra pars reticulata. Our results implicate both of these sites in amphetamine-induced increases in the release of neostriatal ascorbate. Thus, whereas unilateral electrolytic lesions of the substantia nigra pars reticulata completely abolished the ability of systemic amphetamine (2.5 mg/kg) to increase extracellular ascorbate in ipsilateral neostriatum, intranigral infusions of this drug (10 and 30 µg/µl) elevated neostriatal ascorbate release. This infusion effect, moreover, was blocked by electrolytic lesions of the ipsilateral ventromedial thalamus, which receives input from the substantia nigra pars reticulata and projects to the cerebral cortex. These results, combined with previous evidence implicating cortical projections to neostriatum as the source of extracellular ascorbate, suggest that neostriatal ascorbate release is regulated, at least in part, by a nigro-thalamo-cortico-neostriatal pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.63041499.x
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  • 2
    Electronic Resource
    Electronic Resource
    Real-Time Measurement of Electrically Evoked Extracellular Dopamine in the Striatum of Freely Moving Rats (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 68 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The real-time measurement of electrically evoked dopamine was established in brain extracellular fluid of freely moving rats. Dopamine was monitored by fast-scan cyclic voltammetry at carbon fiber microelectrodes lowered into the striatum by means of a detachable micromanipulator. A stimulating electrode, previously implanted in the substantia nigra, was used to evoke striatal dopamine efflux. Evoked extracellular dopamine was both current and frequency dependent. When low current intensities (±125 µA) and frequencies (10–20 Hz) were applied, detectable levels of dopamine were elicited without a perceptible behavioral response. Reproducible concentrations of extracellular dopamine could be evoked in the same rat for at least 2 months. These concentrations, moreover, were significantly higher in freely moving rats compared with rats anesthetized with Equithesin. Analysis of measured curves for dopamine uptake and release rates revealed that anesthesia inhibits release but does not affect uptake. It is concluded that (a) fast-scan cyclic voltammetry at carbon fiber microelectrodes is a viable technique for the measurement of electrically evoked dopamine in brain extracellular fluid of freely moving rats, (b) it is possible to determine in situ rate constants for dopamine release and uptake from these temporally and spatially resolved measurements of levels of dopamine, and (c) transient changes in extracellular dopamine levels elicited by electrical stimulation are affected by anesthesia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.68010152.x
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  • 3
    Electronic Resource
    Electronic Resource
    Dopamine-independent action of cocaine on striatal and accumbal neurons (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Increasing evidence suggests that dopamine (DA) mechanisms alone cannot fully explain the psychoemotional and behavioural effects of cocaine, including its ability to induce drug-taking behaviour. Although it is known that cocaine, after intravenous administration or smoking, may reach brain levels high enough to inhibit Na+ transport, the role of this action remains unclear. To examine the contribution of local anaesthetic and DA mechanisms to changes in striatal and accumbal neuronal activity induced by cocaine, single-unit recording was combined with iontophoresis in awake, unrestrained rats. Most spontaneously active and glutamate-stimulated neurons were highly sensitive to brief cocaine applications (0–40 nA); cocaine-induced inhibitions occurred at small ejection currents (0–5 nA), were dose-dependent, highly stable during repeated applications and strongly dependent on basal activity rates. These neuronal responses remained almost unchanged after systemic administration of either a selective D1 antagonist (SCH-23390, 0.2 mg/kg) or a combination of SCH-23390 (1 mg/kg) and eticlopride (1 mg/kg), a D2 antagonist. Whereas SCH-23390 alone had a weak attenuating effect, no effect and even a slight enhancement of responses to cocaine occurred in fast-firing glutamate (GLU)-stimulated units after the combined blockade of D1 and D2 receptors. Responses to cocaine were mimicked by iontophoretic procaine (0–40 nA), a short-acting local anaesthetic with minimal effect on DA uptake. Procaine-induced inhibitions occurred at the same low currents, had a similar time-course, and were also strongly dependent on basal discharge rate. Our data support the existence of a DA-independent mechanism for the action of cocaine involving a direct interaction with Na+ channels. Although further studies are required to clarify this mechanism and its interaction with other pharmacological and behavioural variables, a direct interaction with Na+ channels may contribute to changes in neuronal activity induced by self-injected cocaine, thereby playing a role in mediating the psychoemotional and behavioural effects of this drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00066.x
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced responsiveness to intraventricular infusion of amphetamine following its repeated systemic administration (1979)
    Springer
    Psychopharmacology 62 (1979), S. 101-102 
    Details
    ISSN: 1432-2072
    Keywords: d-Amphetamine ; Behavioral augmentation ; Intraventricular infusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies have demonstrated that long-term administration of d-amphetamine produces a progressive augmentation of behavior. In the present experiment, rats receiving repeated systemic injections responded to an intraventricular infusion of d-amphetamine with an augmented increase in locomotor activity. These results indicate that central mechanisms, rather than peripheral dispositional factors, subserve the enhanced behavioral response to repeated amphetamine administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00426043
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  • 5
    Electronic Resource
    Electronic Resource
    Differential sensitivity to amphetamine following long-term treatment with clozapine or haloperidol (1982)
    Springer
    Psychopharmacology 77 (1982), S. 360-366 
    Details
    ISSN: 1432-2072
    Keywords: Amphetamine ; Clozapine ; Haloperidol ; Long-term treatment ; Stereotypy ; Supersensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract When rats were pretreated for 8 consecutive days with 2.0 mg/kg haloperidol, injection of 2.5 or 5.0 mg/kg d-amphetamine 2 or 6 days later resulted in a larger increase in oral behaviors and a more prolonged period of focused stereotypy than in saline-pretreated controls. This increased sensitivity to amphetamine is consistent with the effects of a chronic haloperidol-induced increase in dopamine receptor sensitivity. In contrast, long-term treatment with either d-amphetamine or clozapine produced complex changes in the multiphasic behavioral response to amphetamine, which cannot be explained solely by a shift in the sensitivity of dopamine receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00432771
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  • 6
    Electronic Resource
    Electronic Resource
    Neuronal activity in rabbit neostriatum during classical eyelid conditioning (1994)
    Springer
    Experimental brain research 99 (1994), S. 179-190 
    Details
    ISSN: 1432-1106
    Keywords: Caudate ; Putamen ; Extracellular recording ; Classical eyelid conditioning ; Haloperidol ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Extracellular multiple- and single-unit recordings were made from the neostriatum of rabbits during classical eyelid conditioning. Neostriatal neurons processed information regarding the conditioned auditory stimulus (CS) and conditioned eyelid response (CR) as well as the unconditioned stimulus/response (US/UR). These data are consistent with previous reports that neostriatal neurons respond to movement and movement-related sensory stimuli. In most cases, neostriatal neurons increased activity to the US during the early phase of training, but to the CR as training progressed. A close temporal correlation was found between neuronal activity and CR onset with unit discharges typically preceding CR onset by 10–50 ms. The activity of some multiple and single units was monitored after injection of haloperidol, a neuroleptic and dopamine antagonist known to disrupt neostriatal function. Interestingly, haloperidol caused a greater disruption of CRs at low-intensity than at high-intensity CSs, but conditioning-related neuronal activity was disrupted equally at both intensities. These data are discussed in terms of a possible role for the neostriatum in eyelid conditioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239585
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  • 7
    Electronic Resource
    Electronic Resource
    Repeated treatment with ascorbate or haloperidol, but not clozapine, elevates extracellular ascorbate in the neostriatum of freely moving rats (1994)
    Springer
    Psychopharmacology 116 (1994), S. 103-109 
    Details
    ISSN: 1432-2072
    Keywords: Amphetamine ; Ascorbate ; Clozapine ; Haloperidol ; Neostriatum ; Nucleus accumbens ; Voltammetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Acute administration of neuroleptic drugs alters the extracellular level of ascorbate in the neostriatum, and increasing evidence suggests a role for this vitamin in the behavioral, and possibly therapeutic, effects of these drugs. To shed further light on this issue, extracellular ascorbate was recorded in the neostriatum and nucleus accumbens of awake, behaving rats following chronic treatment with either classical (haloperidol) or atypical (clozapine) neuroleptics or ascorbate itself. Electrochemically modified, carbon-fiber microelectrodes were lowered in place the day after the last of 21 daily injections of either haloperidol (0.5 mg/kg, SC), clozapine (20 mg/kg, IP), sodium ascorbate (500 mg/kg, IP) or vehicle. Voltammetric measurements were obtained during quiet rest and following administration ofd-amphetamine (2.5 mg/kg). Repeated treatment with either haloperidol or ascorbate elevated basal extracellular ascorbate and potentiated the amphetamine-induced increase in ascorbate release in neostriatum but not nucleus accumbens. Both treatment groups also showed a significant increase in amphetamine-induced sniffing and repetitive head movements compared to vehicle-treated animals. In contrast, repeated clozapine had no effect on extracellular ascorbate in either neostriatum or nucleus accumbens, but increased the locomotor response to an amphetamine challenge. Thus, to the extent that increases in neostriatal ascorbate exert neuroleptic-like effects, such effects are likely to parallel haloperidol rather than clozapine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244879
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