BACKGROUND Morphine and lidocaine are known to influence the perception of pain. The present study sought to determine the influence of local administration of morphine on lidocaine-induced analgesia in morphine non-dependent (MND), morphine dependent (MD) and morphine withdrawal (MW) animals. METHODS Adult male Wistar rats were divided into four groups: Control, MND, MD and MW rats. Lidocain...

Chronic morphine drives adaptations in synaptic transmission thought to underlie opiate dependence. Here we examine the role of micro-opioid receptor (MOR) trafficking in one of these adaptations, specifically, changes in GABA transmission in the ventral tegmental area (VTA). To address this question, we used a knock-in mouse, RMOR (for recycling MOR), in which genetic change in the MOR promote...

Background: Exercise deprivation has been concluded to have some negative effects on psychological well-being. This study was conducted to find out whether exercise deprivation may lead to morphine dependence in rats. Methods: Forty male Wistar rats weighing 162 ± 9 g were housed in clear plastic cages in groups of two under standard laboratory conditions. The study had two phases. In phase I, ...

Kindling is a very suitable animal model for studying basis mechanisms of epilepsy. In this model , repeated exposure to weak electrical or chemical increases neuronal excitability and there fore decreases the threshold for induction of epileptic seizures. According to abundant distribution of opioid peptides and their receptors in different brain structures and also the role of these receptors...

Extensive 3' alternative splicing of the mu opioid receptor gene OPRM1 creates multiple C-terminal splice variants. However, their behavioral relevance remains unknown. The present study generated 3 mutant mouse models with truncated C termini in 2 different mouse strains, C57BL/6J (B6) and 129/SvEv (129). One mouse truncated all C termini downstream of Oprm1 exon 3 (mE3M mice), while the other...

Given the mounting evidence for involvement of delta opioid receptors in the tolerance and physical dependence of mu opioid receptor agonists, we have investigated the possible physical interaction between mu and delta opioid receptors by using bivalent ligands. Based on reports of suppression of antinociceptive tolerance by the delta antagonist naltrindole (NTI), bivalent ligands [mu-delta ago...

The influence of single and repeated doses of morphine, pentazocine, and chlorpromazine on the latent time of cortical evoked potentials was observed in rats. The evoked potentials were induced by electrical stimulation of the sciatic nerve under the condition of curarization and artificial respiration. The evoked potential consisted of 4 phases. The latent time of the N2 component was prolonge...

The innate immune system modulates opioid-induced effects within the central nervous system and one target that has received considerable attention is the toll-like receptor 4 (TLR4). Here, we examined the contribution of TLR4 in the development of morphine tolerance, hyperalgesia, and physical dependence in two inbred mouse strains: C3H/HeJ mice which have a dominant negative point mutation in...

To explore the effect of sinomenine on the nitric oxide (NO)/neural nitric oxide synthase (nNOS) system in the cerebellum and spinal cord of morphine-dependent and morphine-withdrawal Kunming mice, mice were subjected to injection of morphine with an increasing dose for 5 d, and then were treated with sinomenine (40 mg/kg, i.p.) for another 5 d. Naloxone was used to develop acute withdrawal, an...

Elevation of plasma corticosterone (PCS) has been used as an indicator of morphine withdrawal, but it is not clear whether the magnitude of elevation is related to the intensity of the dependence. The dose-dependent effects of naloxone on PCS and body weight were studied in male Sprague-Dawley rats rendered physically dependent on morphine by injecting increasing doses of 40-120 mg/kg/day, s.c....