effects of intra-central amygdala administration of l-arginine, a nitric oxide precursor, and ng-nitro-l-arginine methyl-ester (l name), a nitric oxide synthase inhibitor, on the morphine-induced sensitization and also on the expression of morphine-induced place conditioning in rats were studied. subcutaneous (s.c.) administration of morphine (2.5, 5 and 7.5 mg/kg) induced place conditioning. r...

In the adult male Sprague-Dawley rat, a species commonly used to study tolerance to the antinociceptive effects of morphine, approximately 10% of the morphine dose is metabolized to normorphine-3-glucuronide (NM3G). In contrast, NM3G is a relatively minor metabolite of morphine in human urine reportedly accounting for approximately 1% of the morphine dose. To date, the pharmacology of NM3G has ...

We investigated the effect of chronic administration of morphine on noxious stimulus-induced antinociception (NSIA) produced by intraplantar capsaicin injection. In the untreated (naive) rat, we previously found that NSIA depends on activation of dopamine, nicotinic acetylcholine, and mu- and delta-opioid receptors in nucleus accumbens. Rats chronically implanted with subcutaneous morphine pell...

Background and Objective: Morphine can cause harmful effects in the ovaries. The silver nanoparticles (Ag-NPs) used in health care because of antimicrobial properties, can diffuse into the brain blood barrier. This study investigated the protective effect of Ag-NPs on the induction of polycystic ovary (PCO) due to injection of morphine intra-ventromedial hypothalamus (intra-VMH) of rat compared...

Acute morphine withdrawal is considered to be the physical manifestation of dependence, emerging when morphine administration is stopped or after the administration of an opiate antagonist, such as naloxone. Gabapentin, which is an antiepileptic, agent, enhances the analgesic effect of morphine in healthy volunteers, but its effect on morphine dependence and withdrawal signs has not determined ...

introduction: n-methyl-d-aspartate (nmda) receptors play a pivotal role in the development of tolerance and physical dependence to opiates. activation of nmda receptors involves the induction of long term potentiation (ltp) in hippocampus. our previous study suggested that chronic oral administration of morphine enhanced nmda dependent ltp in the ca1 area of hippocampal slices of rats. the pres...

Regulation of cAMP-dependent protein phosphorylation by acute and chronic morphine was studied in the rat locus coeruleus (LC), a brain region that appears to play an important role in mediating morphine action in animals, including humans. Rats were treated chronically with morphine under conditions known to induce states of tolerance and dependence. Protein phosphorylation was then studied in...

Clinical observation of a synergistic effect of ketamine on morphine analgesia remains controversial. Although a pharmacodynamic basis for an interaction has been explored in animal and clinical studies, the possibility of a pharmacokinetic mechanism has not been investigated. Whereas both morphine and morphine-6-glucuronide are effective analgesics, morphine-3-glucuronide (M3G) lacks activity....

Altered synaptic transmission and plasticity in brain areas involved in reward and learning are thought to underlie the long-lasting effects of addictive drugs. In support of this idea, opiates reduce neurogenesis [A.J. Eisch et al. (2000) Proceedings of the National Academy of Sciences USA, 97, 7579-7584] and enhance long-term potentiation in adult rodent hippocampus [J.M. Harrison et al. (200...