Pronociceptive effects of remifentanil in a mouse model of postsurgical pain: effect of a second surgery.

Background: Remifentanil anesthesia enhances postoperative pain in animals and humans. The authors evaluated the impact of the dose (microg x kg(-1) x min(-1)) and duration of remifentanil infusion, and the effects of a second surgery on postoperative pain sensitization.

Methods: Mice received different doses of remifentanil over 30 or 60 min.

Compulsive alcohol drinking in rodents.

Upon prolonged alcohol exposure, the behaviour of an individual can gradually switch from controlled to compulsive. Our review is focused on the neurobiological mechanisms that might underlie this transition as well as the factors that are influencing it. Animal studies suggest that temporally increased alcohol consumption during post-abstinence drinking is accompanied by a loss of flexibility of the behaviour and therefore, could serve as a model for compulsive alcohol drinking.

GPR3 receptor, a novel actor in the emotional-like responses.

GPR3 is an orphan G protein-coupled receptor endowed with constitutive Gs signaling activity, which is expressed broadly in the central nervous system, with maximal expression in the habenula. We investigated the consequences of its genetic deletion in several behavioral paradigms and on neurotransmission. Compared to wild-type, hippocampal neurons from Gpr3(-/-) mice displayed lower basal intracellular cAMP levels, consistent with the strong constitutive activity of GPR3 in transiently transfected cells.

The pro-nociceptive effects of remifentanil or surgical injury in mice are associated with a decrease in delta-opioid receptor mRNA levels: Prevention of the nociceptive response by on-site delivery of enkephalins.

The ultra-short-acting mu-opioid receptor (MOR) agonist remifentanil enhances postsurgical pain when used as main anesthetic in animal models and man. Although the mechanism/s involved are poorly characterized, changes in opioid receptor expression could be a relevant feature. Using a mouse model of postoperative pain, we assessed the expression of MOR and delta opioid receptors (DORs) and the efficacy of Herpes Simplex vector-mediated proenkephalin release (SHPE) preventing postoperative nociceptive sensitization induced by remifentanil or surgical incision.

Opioid-induced hyperalgesia in a murine model of postoperative pain: role of nitric oxide generated from the inducible nitric oxide synthase.

Background: Opioid-induced delayed hyperalgesia and allodynia have been reported in human and animal models. The authors evaluated the influence of different opioids used during clinical anesthesia on nociceptive sensitivity and incisional pain in mice. The role of the inducible nitric oxide synthase on surgical pain and opioid-induced pronociception also was investigated.

Influence of the anabolic-androgenic steroid nandrolone on cannabinoid dependence.

The identification of the possible factors that might enhance the risk of developing drug addiction and related motivational disorders is crucial to reduce the prevalence of these problems. Here, we examined in mice whether the exposure to the anabolic-androgenic steroid nandrolone would affect the pharmacological and motivational effects induced by Delta(9)-tetrahydrocannabinol (THC), the principal psychoactive component of Cannabis sativa. Mice received nandrolone using pre-exposure (during 14days before THC treatment) or co-administration (1h before each THC injection) procedures.

Development and expression of neuropathic pain in CB1 knockout mice.

Neuropathic pain is a clinical manifestation characterized by the presence of spontaneous pain, allodynia and hyperalgesia. Here, we have evaluated the involvement of CB1 cannabinoid receptors in the development and expression of neuropathic pain. For this purpose, partial ligation of the sciatic nerve was performed in CB1 cannabinoid receptor knockout mice and their wild-type littermates.

Prevention of fentanyl-induced delayed pronociceptive effects in mice lacking the protein kinase Cgamma gene.

It has recently been reported in several nociceptive models of rats that the antinociceptive effect of fentanyl, an opioid analgesic widely used in the management of per-operative pain, was followed by paradoxical delayed hyperalgesia dependent on N-methyl-D-aspartate (NMDA) mechanisms. Events upstream of the NMDA receptor, especially the activation of the protein kinase Cgamma (PKCgamma), have been involved in the persistence of pain states associated with central sensitisation. In order to evaluate the contribution of the PKCgamma in early and delayed fentanyl nociceptive responses, we studied these effects in knock-out mice deficient in such a protein.

Effects of nandrolone on acute morphine responses, tolerance and dependence in mice.

Anabolic-androgenic steroid exposure has been proposed to present a risk factor for the misuse of other drugs of abuse. We now examined whether the exposure to the anabolic-androgenic steroid, nandrolone, would affect the acute morphine responses, tolerance and dependence in rodents. For this purpose, mice received nandrolone using pre-exposure (for 14 days before morphine experiments) or co-administration (1 h before each morphine injection) procedures.

Fentanyl enhancement of carrageenan-induced long-lasting hyperalgesia in rats: prevention by the N-methyl-D-aspartate receptor antagonist ketamine.

Background: Tissue damage may produce hyperalgesia, allodynia, and persistent pain. The authors recently reported that fentanyl elicits analgesia but also activates N-methyl-D-aspartate-dependent pain facilitatory processes opposing analgesia. In nonsuffering rats, this leads to a long-lasting enhancement in pain sensitivity.