Psychopharmacology
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By acting on peripheral opioid receptors, opioid agonists can attenuate nociceptive responses induced by a variety of agents. ⋯ In this experimental pain model, activation of peripheral mu or kappa opioid receptors can attenuate capsaicin-induced thermal hyperalgesia in rats. It supports the notion that peripheral antinociception can be achieved by local administration of analgesics into the injured tissue without producing central side effects.
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Dopamine plays a major role in the behavioral effects of methamphetamine. ⋯ The present findings in rats support previous research findings in other species indicating a major role of dopamine in the discriminative-stimulus effects of methamphetamine. These findings further indicate involvement of dopamine uptake sites as well as D1 and D2 receptors.
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The elevated plus-maze and the light/dark box are two established anxiety tests in rodents, which are useful to screen putative anxiogenic effects of drugs. ⋯ Adaptative mechanisms following mutation in A(2A) receptors or their long-term blockade after chronic ingestion of caffeine may be responsible for increase proneness to anxiety. However, the short-term anxiety-like effect of caffeine in mice might not be related solely to the blockade of adenosine A(2A) receptors, since it is not shared by A(2A) selective antagonists.