Nociceptin/orphanin FQ (N/OFQ) is the endogenous peptide for the NOP receptors. Depending on the doses, intrathecal administration of N/OFQ has dual actions (ie, hyperalgesia and antinociception) in rodents. However, the pharmacological profile of intrathecal N/OFQ is not fully known in primates. The aim of this study was to investigate behavioral effects of intrathecal N/OFQ over a wide dose r...

Previous reports utilizing pharmacological antagonists implicate kainate receptor (KAR) activation in the development of morphine tolerance, dependence, conditioned place preference (CPP), and locomotor sensitization, but the role of glutamate receptor (GluR) 5-containing KAR in these effects remains unclear because of limited selectivity of the inhibitors employed. Therefore, we examined respo...

Opioid receptor agonists are effective for treating pain; however, tolerance and dependence can develop with repeated use. Combining opioids with cannabinoids can enhance their analgesic potency, although it is less clear whether combined treatment alters opioid tolerance and dependence. In this study, four monkeys received 3.2 mg/kg morphine alone or in combination with 1 mg/kg Δ(9)-tetrahydro...

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 antino...

Current models of endogenous pain control circuitry emphasize neural substrates within the brainstem and spinal cord. We have recently shown, however, that the central nucleus of the amygdala (Ce) contributes to morphine-induced suppression of formalin-induced nociceptive behaviors. In the four experiments reported here, we investigated the possibility that the Ce also contributes to morphine-i...

UNLABELLED To explore further the role of inflammatory processing on peripheral opioid pharmacology, we examined whether the potency of intraarticular (i.a.) or intrathecal (i.t) morphine in tests of thermal and mechanical nociception changed during the induction of experimental arthritis in the rat. Thermal nociception by i.t. morphine (3, 10, and 50 micrograms) or i.a. morphine (100, 1000, an...

We investigated the effects of pretreatment with low-affinity, uncompetitive NMDA receptor antagonists on morphine-induced antinociception in rats using the same intensity of thermal stimulus applied to the tail and the paws. Similar baseline responses to thermal stimuli of the same intensity were recorded from tails and hind paws. However, morphine produced equal antinociception from the tail ...

hanges in the concentration of either brain or blood glucose level appear to modulate antinociceptive and basal nociceptive processes. There are some contradictory data about the effect of diabetes on morphine antinociception. In this study the effects of alloxan-induced diabetes on morphine analgesia, tolerance and dependency were investigated, with a view to clarify the contradictions. Materi...

the amygdala is a forebrain region, which is known as a modulator of pain sensation. the amygdala, particularly the central nucleus, has high concentrations of enkephalins relative to dynorphins and has high concentrations of opioid receptors. we here studied the role of central nuclei of amygdala in morphine antinociception. methods: in this study, we used 130 male wistar rats (200- 250g). bil...