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...

Antinociceptive actions and effects of intracerebroventricular (i.c.v.) dynorphin-(1-13) (DYN) on morphine (MOR) analgesia and acute tolerance were studied in male Sprague-Dawley rats. Antinociceptive effect against hind paw pressure was produced by 30 micrograms of DYN, but not by 0.5-10 micrograms. Acetic acid writhing was inhibited dose-dependently by DYN at the doses of 2-30 micrograms, and...

The possibility that the opioid &receptor mediates antinociception in tests where heat is the noxious stimulus was investigated using highly selective ~and 6-agonists and -antagonists. Antinociceptive dose-response curves were constructed for u ([D-AIa2,NMePhe 4, Gly-ol]enkephalin, DAGO; morphine) and b ([D-Pen2,D-PenS]enkephalin, DPDPE)-agonists in the absence, and in the presence of the/~ non...

Gossypin is a bioflavonoid isolated from Hibiscus Vitifolus Linn. The antinociception activity of gossypin has been studied in comparison with the standard antinociception agent, morphine, against the experimental model of tonic continuous pain produced by formalin. Formalin (0.1ml of 1% solution) was injected under the plantar surface of right hind paw of mice and the time an animal spent in l...

The effects of twice-daily injections of L-arginine or D-arginine (200 mg/kg i.p.) for 4 days on morphine-induced antinociception, brain nitric oxide synthase activity and brain and serum distribution of morphine and brain mu-opioid receptors labeled with [3H][D-Ala2,MePhe4,Gly5-ol]enkephalin were determined in male Swiss-Webster mice. Chronic treatment with L-arginine, but not D-arginine, decr...

We have previously reported the chemistry and antinociceptive properties of a series of glycosylated enkephalin analogs (glycopeptides) exhibiting approximately equal affinity and efficacy at δ opioid receptors (DORs) and μ opioid receptors (MORs). More detailed pharmacology of the lead glycopeptide MMP-2200 [H₂N-Tyr-D-Thr-Gly-Phe-Leu-Ser-(O-β-D-lactose)-CONH₂] is presented. MMP-2200 produced d...

AIMS The current study assessed the in vivo antagonist properties of nalmefene using procedures previously used to characterize the opioid antagonists naloxone, naltrexone, 6beta-naltrexol and nalbuphine. MAIN METHODS ICR mice were used to generate antagonist dose-response curves with intraperitoneal (i.p.) nalmefene against fixed A(90) doses of morphine in models of morphine-stimulated hyper...

The nonopioid actions of spinal dynorphin may promote aspects of abnormal pain after nerve injury. Mechanistic similarities have been suggested between opioid tolerance and neuropathic pain. Here, the hypothesis that spinal dynorphin might mediate effects of sustained spinal opioids was explored. Possible abnormal pain and spinal antinociceptive tolerance were evaluated after intrathecal admini...

Background and Objectives: Previous studies have shown the antinociceptive effect of morphine in animal models, but the specific anti-pain consequence of the abuse drug in female animals is unclear. The present research showed the morphine antinociception in female Wistar rats using formalin test. Materials and Methods: Subjects were 40 female Wistar rats purchased from Pasteur Institute of Ir...