Psychopharmacology
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Clinical Trial Controlled Clinical Trial
Preliminary evidence of attenuation of the disruptive effects of the NMDA glutamate receptor antagonist, ketamine, on working memory by pretreatment with the group II metabotropic glutamate receptor agonist, LY354740, in healthy human subjects.
Some of the behavioral consequences of deficits in N-methyl-D-aspartate (NMDA) glutamate receptor function are thought to arise from the disinhibition of cortical glutamatergic circuitry. ⋯ These data provide preliminary and suggestive evidence that LY354740 or other group II mGluR agonists might play a role in treating working memory impairment related to deficits in NMDA receptor function.
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Comparative Study
Combined discriminative stimulus effects of midazolam with other positive GABAA modulators and GABAA receptor agonists in rhesus monkeys.
Interactions among compounds at GABA(A) receptors might have important implications for the therapeutic and other effects of positive GABA(A) modulators (e.g. benzodiazepines). ⋯ Direct-acting GABA(A) receptor agonists are qualitatively different from positive GABA(A) modulators in rhesus monkeys trained to discriminate midazolam. Although GABA(A) receptor agonists and modulators can enhance the actions of benzodiazepines at the GABA(A) receptor complex, the same drugs do not necessarily modify the discriminative stimulus effects of benzodiazepines. These results underscore the importance of the mechanism by which drugs alter Cl(-) flux at the GABA(A) receptor complex as a determinant not only of drug action but also of drug interaction and whether any particular drug enhances the behavioral effects of a benzodiazepine.
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(1S,2S,5R,6S)-2-Aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740) is a potent and selective agonist for group II metabotropic glutamate (mGlu2 and mGlu3) receptors, with anxiolytic-like activity in animal and human models, and efficacy in anxiety patients. However, the lack of mGlu2 or mGlu3 receptor specific agonists has prevented in vivo characterization of individual functions of these two receptors in mediating the anxiolytic-like effects of LY354740. ⋯ The activation of both mGlu2 and mGlu3 receptors by LY354740 appears to be required for anxiolytic-like activity in the EPM test in mice. These studies serve as a foundation for additional studies on underlying circuits, brain structures, and receptor subtypes involved in the anxiolytic-like actions of mGlu receptor active agents, and the design of future drugs for anxiety disorders in humans.
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Comparative Study
Discriminative stimulus effects in rats of SR-141716 (rimonabant), a cannabinoid CB1 receptor antagonist.
To examine the discriminative stimulus effects of (i) the cannabinoid CB(1) receptor antagonist SR-141716 (SR, 5.6 mg/kg) and vehicle, and (ii) the cannabinoid receptor agonist Delta(9)-THC (THC, 1.8 mg/kg) and vehicle using a discriminated taste aversion (DTA) procedure. ⋯ SR-141716 induces a discriminative stimulus complex in DTA that shows potential for further examination of cannabinoid receptor antagonism.
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Administration of an opiate antagonist following acute morphine exposure elevates the startle response in rodents, a phenomenon that may reflect the anxiogenic effects of withdrawal. Previous acute dependence studies have demonstrated escalated withdrawal severity following multiple withdrawal episodes. ⋯ These data demonstrate that repeated withdrawals from acute morphine exacerbate the severity of potentiated startle and hyperalgesia. These paradigms may be useful in examining the neural plasticity underlying the development of opiate dependence.