It has been described that coadministration of opioids with low doses of other analgesics can reduce adverse effects and increase antinociception, but combinations of two μ-opioid receptor agonists have been poorly explored. The objective of this work was threefold: 1) to evaluate the antinociceptive combination of i.c.v. morphine and fentanyl at different doses; 2) to compare the antinocicepti...

Improgan, a nonopioid antinociceptive agent, activates descending, pain-relieving mechanisms in the brain stem, but the receptor for this compound has not been identified. Because cannabinoids also activate nonopioid analgesia by a brain stem action, experiments were performed to assess the significance of cannabinoid mechanisms in improgan antinociception. The cannabinoid CB(1) antagonist N-(p...

In the present study, the effects of intracuneiformis nucleus microinjection of gamma-aminobutyric acidA (GABAA) receptor agonist and antagonist on antinociception inducced by morphine were investigated with formalin test in rat. Intracuneiformis nucleus microinjection of morphine (10µgr/rat) and Bicuculline (50, 100 ng/rat) induced antinociception in the both first and second phases of formali...

This study was designed to investigate the role of GABAB receptor agents on imipramine-induced antinociception in ligated and non-ligated mice using hot-plate test. The data showed that different doses of morphine (3, 6, and 9 mg/kg) induced a dose-dependent antinociception in ligated and non-ligated mice. However, the opioid response was decreased in ligated animals. Intracerebroventricular (i...

Serotonin specific reuptake inhibitors (SSRI) may induce antinociception however, the mechanism of this effect is not clear. SSRls increase 5-HT levels in neuronal synapses and facilitate serotonergic activity. In this study, therefore, the activity of para-chlorophenylalanine (pCPA), which reduces 5-HT release, and 5- hydroxy tryptophan (5-HTP), a precursor of 5-HT, were examined on the a...

In the present study, the effect of GABA (γ-aminobutyric acid) receptor agonists and antagonists on morphine-induced antinociception was investigated in formalin test in rats. Intraperitoneal (i.p.) injection of different doses of morphine (1, 3, 6 and 9 mg/kg) and intracerebroventricular (i.c.v.) injection of different doses of muscimol (0.5, 1 and 2 g/rat) or baclofen (0.25, 0.5 and 1 g/rat) ...

We report an anatomically defined opioid-responsive site in the rostral agranular insular cortex (RAIC) of the rat and characterize the antinociception produced by morphine acting within this region. Immunohistochemistry for the mu-opioid receptor identified a discretely localized cluster of densely labeled dendrite-like processes in the agranular insular cortex. The antinociceptive effect of m...

UNLABELLED To clarify the supraspinal and spinal actions of a cholinergic agonist, carbachol, and an opioid, oxycodone, we studied their antinociceptive and behavioral effects when administered into brainstem medial pontine reticular formation (mPRF) or spinal subarachnoid space with or without pretreatment of muscarinic receptor subtype antagonist. Sprague-Dawley rats were implanted with a 24-...

Orphanin FQ/nociceptin (OFQ/N), the endogenous ligand for the orphan receptor-like/kappa(3)-like opioid receptor clone, produces a variety of behavioral responses, including those associated with pronociception and antinociception. The OFQ/N precursor rattus-proOFQ (rppOFQ/N) contains several paired basic amino acids, which raises the possibility that post-translational processing can be respon...

1. Orphanin FQ (OFQ), an endogenous peptide for ORL1 receptors, has been identified. Although the actions of OFQ have much in common with those of opioid peptides at the cellular level, behavioral studies in rodents seem conflicting. 2. The aim of this study was to investigate the potential pronociceptive or antinociceptive function of peripheral ORL1 receptors in primates. Experiments were con...