mice were rendered tolerant and dependent to morphine by subcutaneous injection of morphine over a period of 5 days. the effects of acute and chronic administration of dihydropyridine calcium channel antagonist nifedipine on the development of tolerance and naloxone-precipitated morphine withdrawal signs were investigated. a single injection of nifedipine proved to be effective in inhibiting so...

previous studies have shown that the extract of papaver rhoeas reduces morphine dependence, locomotor activity and reward. in present study, the effects of hydro-alcohol extract of papaver rhoeas on the tolerance to analgesic effects of morphine in mice have been investigated using tail flick method. subcutaneous (s.c.) administration of morphine (1, 2, 5 and 10 mg/kg) induced analgesia. howeve...

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 ...

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 ...

introduction: several researches have reported that stress is able to inhibit the development of morphine tolerance via activating of hypothalamic-pituitary-adrenal (hpa) axis. in the present study we tried to examine the effect of epinephrine, the product of adrenal medulla, on the development of morphine tolerance. methods: analgesic tolerance was induced by intrathecal (i.t.) injection of mo...

Background: Tolerance and dependence to anti-nociceptive effect of morphine restricted its use. Nowadays co-administration of morphine and other drugs suggests diminishing this tolerance. Baclofen is one of the drugs that may be beneficial in the attenuation of tolerance to morphine. Studies have shown that changes in transient receptor potential vanilloid type 1 (TRPV-1) expression during admi...

Introduction: The GABAergic system of the brain plays a key role in morphine tolerance and sensitization. As isoniazid is a modulator of the GABAergic system, the present study aims to understand whether isoniazid can influence the induction of tolerance and sensitization to the rewarding effects of morphine.  Methods: The rewarding effects of morphine and isoniazid were assessed using a Condi...

introduction: in order to study the alterations of beta 1 and 2 integrins mrna level in rat lumbar spinal cord following the induction of chronic pain and its effect on the development of tolerance to morphine analgesia, we examined the level of expression of these genes in the presence of chronic pain, which is an inhibitor of morphine tolerance. we used induction of chronic pain alone and in ...

introduction: sex differences are observed in the development of tolerance to antinociceptive effect of opioid drugs such as morphine, but the underlying mechanisms remain unclear. critical role of glutamate in the development and maintenance of opioid tolerance has been reported by many investigators. there are also evidences about interaction between gonadal hormones and neuromodulatory syste...

the effect of nmda (n-methyl-d-aspartate) receptor antagonists on tolerance to morphine antinociception was investigated in mice. daily subcutaneous administration of 50 mg/kg of morphine hydrochloride for three days induced tolerance to different (3,6 and 9 mg/kg) test doses of morphine. the tolerance obtained was decreased by pretreatment of animals with single or repeated doses of competitiv...