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  • 1
    ISSN: 1432-2072
    Keywords: Cholinergic function ; Acetylcholine ; Choline ; Levels ; Turnover rates ; Gas chromatography ; Lead poisoning ; Malnutrition ; Central nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were exposed to lead acetate from birth, and were killed at the age of 44–51 days for analysis of levels and turnover rates of acetylcholine (ACh). Steady-state levels of ACh were not altered in midbrain, cortex, hippocampus, or striatum of lead-exposed rats. Similarly, no changes in choline (Ch) concentrations were found in cortex, hippocampus, or striatum. In the midbrain, however, a 30% reduction in Ch levels was observed. Changes in specific activity of Ch and ACh were measured as a function of time in selected brain areas of rats infused with a radio-labeled precursor of Ch. Specific activities of ACh were not altered. Ch specific activities were, however, significantly elevated in all brain areas examined, as compared with age-matched control rats. The in vivo ACh turnover rate in cortex, hippocampus, midbrain, and striatum was diminished by 35%, 54%, 51% and 33%, respectively. These findings provide direct evidence for an inhibitory effect of lead exposure from birth on central cholinergic function in vivo. Since a significant reduction of body weight was found in those animals treated with lead acetate, the alteration of central cholinergic function may partially be attributed to malnutrition observed in the lead-exposed animals.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Methylphenidate ; Lead toxicity ; Cholinergic and catecholaminergic effects ; Mesencephalic reticular formation ; CNS ; Hyperkinesis ; Supersensitivity ; Oxotremorine ; Nicotine ; Model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of methylphenidate (MPH) and the cholinergic agonists nicotine and oxotremorine were tested on the spontaneous multiple unit activity in the mesencephalic reticular formation of two groups of rats. In control rats i.v. MPH (1 mg/kg), nicotine (0.125 mg/kg), and oxotremorine (0.5 mg/kg) all attenuated the unit activity with latencies of less than 10 min. In another group of rats, exposed to lead acetate since birth, the extent of attenuation of unit activity induced by MPH and nicotine was reduced and the latency of effect was delayed by 45–50 min. The latency of the oxotremorine effect was not changed but the attenuation of unit activity was more pronounced in the lead-treated group. Pretreatment with spiroperidol, to inhibit the aminergic receptors, diminished the inhibitory effect of MPH in the control group but not in the lead-treated group, whereas the attenuating effect of oxotremorine was not affected in either group. These data support our previous evidence that MPH exerts its action in the central nervous system by a cholinergic pathway in addition to published catecholaminergic pathways. Furthermore, the present findings indicate that chronic leadexposure in rats results in cholinergic hypofunction and supersensitivity at central cholinergic receptor sites. This alteration of central cholinergic function may be partially attributed to the malnutrition observed in the lead-exposed animals.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Methylphenidate ; Hyperkinesis ; Mesencephalic Reticular Formation ; Thalamus ; Attention ; Arousal ; CNS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intravenous administration of methylphenidate (1 or 2 mg/kg) markedly attenuated the unit discharge rate in the mesencephalic reticular formation of rats and cats. Concurrently this drug enhanced the neural activity in the primary sensory nuclei of the thalamus. The differential effects of methylphenidate on these two neural systems suggest a possible mechanism by which it may improve attentive processes in hyperkinesis.
    Type of Medium: Electronic Resource
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