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  • 1
    ISSN: 1432-2072
    Keywords: Scopolamine ; Spiperone ; Dopamine receptors ; Neural interactions ; Locomotor activity ; Presynaptic mechanisms ; Apomorphine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Scopolamine reversed the reduction in avoidance responding caused by spiperone and antagonized the inhibitory effects of spiperone on the behavioral actions of d-amphetamine or apomorphine. Scopolamine-induced locomotor activity was greater in 6-hydroxydopamine (6-OHDA)-treated animals than in controls. This increase was prevented by administration of α-methyltyrosine, but not by inhibition of dopamine-β-hydroxylase, indicating that this action of scopolamine was associated with presynaptic dopaminergic fibers. Therefore, the possibility that pre-synaptic dopaminergic function was the locus of the antagonism of spiperone by scopolamine was examined using drug interaction studies in 6-OHDA-treated rats. However, when 6-OHDA-treated rats were given α-methyltyrosine, scopolamine still reversed the spiperone blockade of apomorphine-induced locomotion. Although these data provided evidence for a post-synaptic action for this cholinergic blocking agent, scopolamine affected neither dopamine-stimulated adenylate cyclase activity nor 3H-spiperone binding in vitro. Furthermore, scopolamine did not alter the level of specific 3H-spiperone binding found in brain after in vivo administration. This suggests that the postsynaptic mechanism affected by scopolamine is different from the site affected by spiperone. Thus, it is concluded that scopolamine can affect both pre- or post-synaptic events associated with dopaminergic function and that both may contribute to the reversal of the actions of spiperone.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Fenmetozole ; Ethanol ; Aerial righting reflex ; Conflict behavior ; Guanosine 3′,5′-monophosphate ; Physical dependence ; Physiological antagonism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The selectivity and specificity of fenmetozole (DH-524) [2(3,4-dichlorophenoxy-methy))2-imidazole HCl] as an antagonist of the actions of ethanol were examined. Fenmetozole (15–30 g/kg) reduced ethanol-induced impairment of the aerial righting reflex without changing blood or brain ethanol content, indicating that the antagonistic actions of fenmetozole were not due to change in the pharmacokinetics of ethanol. Since fenmetozole also reduced aerial righting reflex impairment due to phenobarbital, chlordiazepoxide, and halothane, this action of fenmetozole was not specific to ethanol. In mice, both the ethanolinduced increase in locomotor activity at 2.0 g/kg and the decrease caused by 4.0 g/kg were antagonized by fenmetozole. In addition, fenmetozole attenuated the ethanol-induced reduction in cerebellar cyclic guanosine monophosphate (cGMP) content, but the drug also significantly elevated cGMP levels in this tissue when given alone. Fenmetozole did not alter ethanolinduced increases in punished drinking in a conflict test, except at a high dose which alone decreased both punished and unpunished responding. Fenmetozole also failed to precipitate ethanol withdrawal-like reactions when given to physically-dependent, intoxicated rats. Thus, the antagonistic action of fenmetozole against ethanol would not seem to be related to a specific receptor interaction but rather may be the result of a physiological antagonism.
    Type of Medium: Electronic Resource
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