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  • 1
    ISSN: 1432-1106
    Keywords: MPTP ; Paradoxical sleep ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In a previous study, we reported on a selective and long-lasting paradoxical sleep (PS) deprivation in cats following repeated administration of the Parkinson syndrome-inducing neurotoxin N-methyl-4-pheny11,2,3,6-tetrahydropyridine (MPTP). While the characteistic motor deficits occurred only from the 2nd to 3rdday of a 5-day long administration of 5 mg/kg per day MPTP i.p., the PS deprivation started immediately after the first injection and lasted altogether for 11–13 days. The motor deficiencies induced by repeated administration of MPTP are mainly due to the selective depletion of dopaminergic neurons in the nigrostriatal system as the histological and biochemical data show. The immediate onset of PS deprivation and the PS recovery, despite the definite cell loss, suggests a mechanism independent of cell destruction. In our present study we investigated the occasional histological and the PS-deprivatory effect of a single low dose of MPTP in cats. A single injection of 2 mg/kg MPTP i.p. resulted in PS deprivation lasting for 2.5–3.5 h. The duration of other sleep stages showed no significant change and PS recovery was without rebound phenomenon, as in the case of repeated administration. Even a higher single dose of MPTP (5 mg/kg) resulted in no visibly detectable nigrostriatal cell loss. We suggest that the changes in monoamine release and/or turnover are involved in the PS deprivatory effect of MPTP.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Key words Microdialysis ; Intravenous ; Psychostimulant ; Yoked ; Mesolimbic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract   Rationale: The neurochemical effects of psychostimulant exposure may depend on how these drugs are encountered. A useful method for examining this issue is to compare neurotransmitter release following response-dependent, or self-administered, drug exposure and response-independent exposure. Objectives: This experiment examined the effect of active and passive cocaine administration on acetylcholine (ACh) efflux in the shell region of the nucleus accumbens (NAc) in rats. Methods: One group of rats (CSA: cocaine self-administration) was trained to lever-press for intravenous infusions of cocaine (0.42 mg/kg per infusion) on a fixed-ratio-1 schedule of reinforcement. Cocaine infusions were accompanied by the onset of a stimulus light that signaled a 20-s time-out period. Control rats received intravenous cocaine (cocaine non-contingent: CNC) or saline (SAL) in a manner that was not contingent upon their behavior. Drug infusions in these groups were determined by the lever-press behavior of the animals in the CSA group, i.e. they were yoked to rats in the self-administration group such that CNC animals received equal amounts of cocaine as CSA rats. Animals received cocaine or saline in 3-h sessions for 13 consecutive days before testing. On day 14, extracellular ACh was measured in 15-min intervals before, during and after a 3-h session of cocaine exposure using unilateral microdialysis probes located in the NAc shell coupled with HPLC. Results: ACh efflux was significantly increased above baseline in both groups of rats that received cocaine but CSA rats had significantly higher ACh levels during the self-administration period compared to their yoked counterparts. In addition, ACh efflux remained elevated longer in CSA animals relative to CNC rats following cessation of cocaine exposure. Conclusions: These results demonstrate that ACh interneurons in the NAc shell are responsive to cocaine exposure. In addition, these findings suggest that the manner in which the drug is administered (i.e. either by active self-administration or passive exposure) may be relevant to the magnitude of the neural response.
    Type of Medium: Electronic Resource
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