in the present study, interactions of dopamine receptor agonists and antagonists with water swimming stress (wss) on naloxone-induced jumping in morphine-dependent mice were examined. mice were rendered dependent as described in the methods section. the opioid receptor antagonist, naloxone (1 mg/kg), was injected to elicit jumping (as a withdrawal sign). the first group exposed to wss in the pr...

This study investigated the effect of bergamot essential oil (BEO) or linalool, a major volatile component of BEO, on the nociceptive response to formalin. Plantar subcutaneous injection of BEO or linalool into the ipsilateral hindpaw reduced both the first and late phases of the formalin-induced licking and biting responses in mice. Plantar subcutaneous injection of BEO or linalool into the co...

Dynorphin peptides act preferentially at kappa- as well as mu- and delta-opioid receptors. This study was conducted to determine whether dynorphin peptides act to lower dopaminergic tone in the tuberoinfundibular system, resulting in elevated serum prolactin levels and, if so, whether such an effect is mediated by the opioid receptors. Dose-related increases in serum prolactin levels were obser...

Stimulation of the delta(1)-opioid receptor has been shown to trigger ischemic preconditioning (IPC). Additionally, myocardial ischemia/reperfusion induces the activation of extracellular signal-regulated kinase (ERK). Therefore, we examined the role of ERK in acute cardioprotection induced by delta(1)-opioid receptor stimulation or IPC. Infarct size (IS) was expressed as a percentage of the ar...

In the present study, the effects of intra-hippocampal microinjections of morphine (an opioid agonist) and naloxone (an opioid antagonist) were investigated in the formalin-induced orofacial pain in rats. Orofacial pain was induced by subcutaneous injection of formalin (1 %, 50 μl) in the upper lip region and the time spent of face rubbing was measured in 3-min blocks for 45 min. Formalin induc...

Long-term blockade of brain opioid receptors by the opiate antagonist naltrexone increases methionine-enkephalin content in the striatum and nucleus accumbens (Tempel et al., 1984). To determine whether these changes in peptide levels reflect increased peptide synthesis, we examined preproenkephalin mRNA content in discrete brain regions of control (placebo-treated) and chronic naltrexone-treat...

Salvia divinorum is a hallucinogenic plant used by the Mazatec Indians of Mexico for traditional spiritual ceremonies. The active constituent, salvinorin A, induces profound hallucinations, however the biological mechanism for this action is not known. Affinity-binding studies suggest that the biologic activity of salvinorin A involves the kappa-opioid receptor. The purpose of this study was to...

the effect of short term usage of gnrh antagonist as pretreatment on superovulation in goats was evaluated. statistical analysis was performed using t-test and showed that usage of gnrh antagonist as pretreatment can improve number of recovered embryos (p0.05). this study showed that usage of gnrh antagonist can improve superovulatory response in term of embryo recovery in goats .this study sho...

BACKGROUND Morphine pretreatment via activation of delta1-opioid receptors induces cardioprotection. In this study, the authors determined whether morphine preconditioning induces ischemic tolerance in neurons. METHODS Cerebellar brain slices from adult Sprague-Dawley rats were incubated with morphine at 0.1-10 microM in the presence or absence of various antagonists for 30 min. They were the...

Pentazocine is a widely used mixed agonist-antagonist opioid. Previous animal studies have demonstrated that pentazocine-induced antinociception displayed a ceiling effect characterized by biphasic dose response with a increasing and then descending analgesia like a bell-shaped curve. This study attempted to clarify the mechanisms underlying such dose-response relationships. ddY and C57BL/6J mi...