in vivo microdialysis was used to study the effects of morphine on glutamate release from the ventral tegmentum area (vta) in freely moving rats. intraperitoneal (i.p.) injection of acute and repeated morphine at increasing doses significantly enhanced glutamate release. only a minor tolerance developed to this dosage of morphine. ap-s (2-amino-5-phosphonovaleric acid, 0.5 mg/kg i.p.), a nmda r...

Morphine and other mu opioids mimic and/or modulate the discriminative stimulus (DS) effects of cocaine, possibly reflecting mutual stimulation of mesolimbic dopamine activity. Less is known about the capacity of cocaine and related stimulants to modulate the DS effects of morphine. The present study investigated the effects of cocaine, amphetamine, and reference drugs, administered alone and w...

According to some studies, the number of addicted females in reproductive ages has been increased. The present study was designed to investigate the effect of oral morphine consumption on the development of CNS and body growth in rats. For this purpose, female Sprauge-Dawley rats were divided into control and experimental groups (20 animals in each group). Maintenance dose of morphine (0/4 mg/m...

According to some studies, the number of addicted females in reproductive ages has been increased. The present study was designed to investigate the effect of oral morphine consumption on the development of CNS and body growth in rats. For this purpose, female Sprauge-Dawley rats were divided into control and experimental groups (20 animals in each group). Maintenance dose of morphine (0/4 mg/m...

Introduction: There is some evidence supporting the reduced activity of integrins following chronic administration of morphine. This reduction might play a role in morphine tolerance development. Manganese binds to the extracellular domain of integrins and makes them to be activated. The effect of integrins activation using manganese on tolerance development to the analgesic effect of morphine ...

BACKGROUND Alpha 2 (α(2))-adrenoceptor agonists may be useful for their potential to increase or prolong opioid analgesia while attenuating the development of opioid tolerance. The purpose of this study was to investigate the effects of dexmedetomidine and guanfacine (α(2)-adrenoceptor agonists) on morphine analgesia and tolerance in rats. METHODS Adult male Wistar albino rats weighing 195-20...

The radiolabelled opioid receptor binding affinities of morphine and its active metabolite morphine 6-glucuronide at the total mu, mu 1, mu 2 and delta receptors were determined. Morphine 6-glucuronide was found to have a 4-fold lower affinity for the mu 2 receptor (IC50 17 nm and 82 nm for morphine and morphine 6-glucuronide respectively, P = 0.01), the receptor postulated to be responsible fo...

Morphine administered simultaneously to intracerebroventricular (i.c.v.) and intrathecal (i.t.) sites exhibits synergism, with the antinociceptive potency much greater than would be predicted from a simple addition of the potencies of the same dose administered to either site alone. This synergism was quantified in mice using both a fixed dose method, in which the morphine dose at one site was ...