Several studies have demonstrated that nitric oxide (NO) is involved in hyperalgesia induced by NMDA activity in Morphine tolerance and NO synthase inhibitors can attenuate hyperalgesia in morphine tolerance. In addition, one of the possible mechanisms in morphine tolerance is reduction of GABA inhibitory effect. For this reason, we used GABA agonists (muscimol and baclofen) to investigate the ...

in this study, the effects of acute and chronic lithium on nociception induced by formalin and its interactions with morphine-induced analgesia were studied in mice. formalin test was selected to study nociception. subcutaneous injection of different doses of morphine (1.5, 3 and 6 mg/kg) induced analgesia in a dose dependent manner in both phases of the formalin test. intraperitoneal administr...

This study aimed to assess the effect of intra-habenular injection of morphine on acute trigeminal pain in rats. Also here, we examined the involvement of raphe nucleus opioid and 5HT3 receptors on the antinociceptive activity of intra habenular morphine to explore the possibility of existence of descending antinociceptive relay between the habenula and raphe nucleus. The numbers of eye wiping ...

The paper by Grach et al. [1] in the Journal addresses the little explored potential benefit of combination opioids in analgesia. Compared with a published study documenting oxycodone-morphine synergy in rats [2], the antinociception study by Grach et al. in healthy subjects has significant design limitations to support their conclusions. In rats, antinociception dose–response curves were produ...

The modulatory role of allosteric receptor-receptor interactions in the pain pathways of the Central Nervous System and the peripheral nociceptors has become of increasing interest. As integrators of nociceptive and antinociceptive wiring and volume transmission signals, with a major role for the opioid receptor heteromers, they likely have an important role in the pain circuits and may be invo...

Activation of brain nociceptin/orphanin FQ (NOP) receptors leads to attenuation of mu-opioid receptor (MOP receptor)-mediated antinociception. Buprenorphine, a high-affinity partial MOP receptor agonist also binds to NOP receptors with 80 nM affinity. The buprenorphine-induced inverted U-shaped dose-response curve for antinociception may be due to NOP receptor activation, given that, in the pre...

To obtain benzomorphans with a longer duration of action that may be potential therapeutics for treating cocaine abuse, 8-carboxamidocyclazocine was synthesized. The pharmacological properties of 8-carboxamidocyclazocine were compared with the parent compound cyclazocine. Changing the 8-hydroxyl group on cyclazocine to an 8-carboxamido group resulted in only a 2-fold decrease in the affinity of...

AIM To examine the role of cholinergic neurons in the nucleus raphe magnus (NRM) in noxious heat stimulation and in the effects of morphine-induced antinociception by rats. METHODS After the cholinergic neuron selective toxin, AF64A, was microinjected into the NRM, we examined changes in the antinociceptive threshold and effects of morphine (5 mg/kg, ip) using the hot-plate (HP) and tail-flic...

effects of insulin (1, 2 and 3 iu/kg, i.p.), morphine (5mg/kg, i.p.), naloxone (5mg/kg, s.c.), insulin before morphine and after naloxone were studied in the formalin test of mice. formalin test was induced by intraplantar injection of formalin (20m, 5%). morphine alone and insulin with morphine decreased the first phase (0-5 min) of pain. naloxone increased the interphase (6-20 min) of nicicep...

( )-6-Phosphonomethyl-deca-hydroisoquinoline-3-carboxylic acid (LY235959) is a competitive N-methyl-D-aspartate receptor antagonist shown to prevent the development of tolerance to the antinociceptive effects of morphine in rodents. Although administration of LY235959 alone generally does not produce antinociception, LY235959 potentiates the antinociceptive effects of morphine in squirrel monke...