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A specific role for the dopamine D3 receptor in behavior has yet to be elucidated. We now report that dopamine D2/D3 agonists elicit dose-dependent yawning behavior in rats, resulting in an inverted U-shaped dose-response curve. A series of experiments was directed toward the hypothesis that the induction of yawning is a D3 receptor-mediated effect, whereas(More)
The effects of self-administered 3,4-methylenedioxymethamphetamine (MDMA) on behavior and neurochemistry have not been previously studied in laboratory primates. We investigated the capacity of MDMA and its enantiomers to maintain contingent responding over an extended duration, whether any decrements in the reinforcing effects of these compounds would be(More)
The binding parameters of radiolabeled DAMGO (mu), DPDPE and pCl-DPDPE (delta) and 5 alpha, 7 alpha, 8 beta-N-methyl-N-[7-(1- pyrrolidinyl)-1-oxaspiro(4,5)dec-8-yl]benzeneacetamide (also known as U69593, kappa) and the affinity and selectivity profiles of various opioid agonists and antagonists at the three opioid receptor types were determined in membranes(More)
Evaluation of the discriminative stimulus effects of drugs is a useful procedure for identification of receptor mediation of in vivo drug effects. This assay can be enhanced when the stimulus effects of different doses of agonist are evaluated. In the present study, rats were trained to discriminate small or large doses of nicotine from saline, and(More)
The present study examined the effect of drug and reinforcement history on quinpirole-maintained responding in rats. Quinpirole (0.01, 0.032, or 0.1 mg/kg per injection) was assessed as a reinforcer in experimentally naive rats, as well as in rats trained to self-administer cocaine, remifentanil, ketamine, or food under a fixed ratio 1 schedule of(More)
RATIONALE Few studies have directly compared the effects of methylenedioxymethamphetamine (MDMA, "ecstasy") and its enantiomers across measures. OBJECTIVES To investigate the capacity of MDMA and its stereoisomers to produce aggregate toxicity in mice, the influence of 5-HT(2) receptors, 5-HT transporters, and ambient temperature on this effect, and to(More)
1-Benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (TFMPP) are two designer drugs that are often sold in combination tablets via the internet. The discriminative stimulus properties and reinforcing effects of these compounds have not previously been assessed in laboratory primates. In this regard, the reinforcing effects of BZP and TFMPP(More)
D2-like agonists, such as quinpirole, maintain responding in monkeys, rats, and mice when they are substituted for cocaine. This study examined the influence of operant history and cocaine-paired stimuli (CS) on quinpirole-maintained responding in rats trained to nose poke for cocaine. Upon acquisition of responding for cocaine, substitutions were performed(More)
Naltrexone (NTX) exhibited approximately 3-fold higher affinity for sites labeled by [3H]U69,593 (putative kappa 1-selective ligand) than [3H]bremazocine (non-selective ligand) in the presence of mu and delta receptor blockade in monkey brain membranes. This led us to test an hypothesis that NTX could display in vivo antagonist selectivity for kappa(More)
Dopaminergic (DA) agonist-induced yawning in rats seems to be mediated by DA D3 receptors, and low doses of several DA agonists decrease locomotor activity, an effect attributed to presynaptic D2 receptors. Effects of several DA agonists on yawning and locomotor activity were examined in rats and mice. Yawning was reliably produced in rats, and by the(More)