Stuart A Dunbar

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BACKGROUND MK801, an N-methyl-D-aspartate receptor antagonist, has recently been reported to attenuate tolerance to, and withdrawal from morphine. This study analyzes tolerance and withdrawal in a chronic intrathecal coinfusion model of morphine and MK801. METHODS Intrathecal catheters, attached to 7-day miniosmotic infusion pumps, were implanted in rats(More)
Because of remifentanil's unique pharmacokinetics, its systemic administration may be suitable for clinical settings where a potent, fast-acting, systemic mu-opioid with a rapid recovery is required, e.g., short painful intervention in the emergency room or the intensive care unit, or procedures in the day surgery or endoscopy suite. Total intravenous(More)
Systemic L-NG-nitroarginine methyl ester or L-NAME (LN), a nitric oxide synthase inhibitor, has been reported to attenuate systemic opioid tolerance and withdrawal. Intrathecal co-administration of LN (100 and 500 nmol/microliter per h) with spinal morphine produced only a small diminishing attenuation of tolerance and attenuated only one of seven signs of(More)
The magnitude of tolerance and dependence is defined in part by agonist concentration and duration of receptor exposure. Therefore, in the face of continued exposure to an opioid agonist, periodic reduction in opiate receptor occupancy should reduce tolerance. Alternately, we have shown that reversal of opiate agonist action yields increased glutamate(More)
The opioid abstinence syndrome is associated with spinal excitatory amino acid (EAA) release, hyperalgesia and long-term changes in dorsal horn cellular excitability. N-Methyl-D-aspartate (NMDA) receptor antagonism attenuates opioid tolerance but also blocks EAA release during abstinence. This study examines the effect of repetitive abstinence, and NMDA(More)
Chronic opioid administration is associated with altered nociception. The mechanisms underlying these changes are not fully understood. Nociceptive transmission within the spinal cord is modulated by both excitatory and inhibitory neurotransmitters. Using spinal microdialysis, the effects of recurrent withdrawal on the release of gamma-aminobutyric acid(More)
BACKGROUND Prostaglandin E(2) is an important spinal modulator of nociception. However, the effects of chronic opioid administration and withdrawal on prostaglandin E(2) release and associated signaling pathways in the spinal cord are generally unknown. METHODS This study sought to examine these effects using a spinal microdialysis technique in a model of(More)
UNLABELLED The analgesic mechanism of epidural steroids in reducing pain associated with degenerative spinal disease (DSD) is poorly understood. We report increased inline epidural infusion pressure in patients with DSD and assess whether this phenomenon is affected by administration of an epidural steroid injection. We collected data during epidural(More)
Naloxone administration in the opioid dependent rat is associated with spinal glutamate release and NMDA receptor activation which reportedly is also responsible for opioid tolerance. We hypothesized that episodic withdrawal during chronic infusion of spinal morphine might paradoxically enhance tolerance. Rats (24/group) infused with intrathecal morphine(More)