Opiate dependence and withdrawal have long been hypothesized to enhance the reinforcing effects of opiates; however, opiate agonist self-administration in these states has yet to be systematically assessed. To address this issue, the reinforcing property of the short-acting -opioid agonist, remifentanil, was assessed in morphine-dependent (MD), morphine-dependent and -withdrawn (MW), and nondep...

Rats were trained to discriminate 4-h pretreatment with 10 mg/kg morphine and 15-min pretreatment with 0.3 mg/kg naltrexone (morphine-->naltrexone) from pretreatment with saline and 0.3 mg/kg naltrexone (saline-->naltrexone). The discrimination seems to derive from interoceptive stimuli from antagonist-precipitated withdrawal from acute morphine dependence. The purpose of this study was to exte...

The cerebrospinal fluid-contacting nucleus (CSF-CN), distributes and localizes in the ventral periaqueductal central gray (PAG) of the brainstem, which may influence actual composition of the cerebrospinal fluid (CSF) for non-synaptic signal transmission via releasing or absorbing bioactive substances. Many experiments have demonstrated that substance P (SP), a substance that is shown to be up-...

The mechanisms of drug dependence and rewarding properties of opiates are not exactly known and several neurotransmitters seem to be involved. It is possible that the rennin-angiotensin system could interact with the opioid system, since it has been shown that angiotensin II(Ang) and ACE inhibitors have analgesic, anticonvulsant and antidepression effects and in some cases they could antagonize...

there is growing evidence indicating that neuronal calcium channels play an important role in the mechanism of morphine dependence. in this study, the effects of acute and chronic administration of nitrendipine on naloxone precipitated morphine withdrawal signs were investigated. mice were rendered dependent to morphine by subcutaneous injection of morphine over a period of 5 days. in chronic s...

background: cuminum cyminum fruit essential oil (feo) dose-dependently can attenuate the expression of morphine tolerance and dependence in morphine-dependent mice. objective: in this study, the effects of cuminum cyminum feo on acquisition and expression of morphine-induced conditioned place preference (cpp) in morphine-sensitized mice were studied. methods: repeated subcutaneous (s.c.) admini...

We have previously reported that the administration of cyclo(Leu-Gly) to mice prior to morphinization blocked the development of tolerance to the analgesic effects of morphine as well as the development of some signs of physical dependence. In the present series of experiments, the effect of the same peptide treatment on changes in dopamine receptor sensitivity induced by chronic morphine treat...

BACKGROUND Morphine has been widely used as a clinical anesthetic and analgesic. However, abuse of morphine might result in psychological and physiological dependence. Previous studies have indicated that memory mechanisms play critical roles in morphine dependence. METHODS Morphine dependence was established in mice utilizing place preference conditioning (CPP). We observed changes in the me...

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...

Maternal deprivation can trigger long-lasting molecular and cellular modifications in brain functions and might facilitate the appearance of pathogenic behaviors. This study focuses on the vulnerability to develop morphine dependence in adult rats that were separated from their mother and littermates for 3 h per day for 14 d after birth and examines the adaptive changes in the enkephalinergic p...