Buprenorphine is a potent opioid analgesic with partial agonistic properties at mu-opioid receptors. This study investigated the interaction potential with several full mu-agonists in the tail-flick test in mice. We further examined the reversibility of buprenorphine antinociception by different mu-opioid receptor antagonists. Combination of buprenorphine with morphine, oxycodone, hydromorphone...

Opioids elicit antinociception in mammals through three distinct types of receptors designated as mu, kappa and delta. However, it is not clear what type of opioid receptor mediates antinociception in non-mammalian vertebrates. Radioligand binding techniques were employed to characterize the site(s) of opioid action in the amphibian, Rana pipiens. Naloxone is a general opioid antagonist that ha...

The present study examined protein kinase A (PKA) and protein kinase C (PKC) involvement in the maintenance of cellular tolerance to mu opioid receptor agonists resulting from chronic opiate exposure in neurosecretory cells of the hypothalamic arcuate nucleus (ARC). The possibility that the diminution of mu opioid receptor/effector coupling produced by acute 17beta-estradiol or chronic opiate e...

BACKGROUND Opioid receptors mediate cardiac ischemic preconditioning. Remifentanil is a new, potent ultra-short-acting phenylpiperidine opioid used in high doses for anesthesia. The authors hypothesize that pretreatment with this drug confers cardioprotection. METHODS Male Sprague-Dawley rats were anesthetized and the chest was opened. All animals were subjected to 30 min of occlusion of the ...

Exposure to stressful or fear-inducing environmental stimuli activates descending antinociceptive systems resulting in a decreased pain response to peripheral noxious stimuli. Stimulating mu opioid receptors in the basolateral nucleus of the amygdala (BLA) in anesthetized rats produces antinociception that is similar to environmentally induced antinociception in awake rats. Recent evidence sugg...

Opioid receptors are currently classified as mu, delta, and kappa types, but various subtypes have also been proposed. We have investigated whether subtypes exist by using [3H]bremazocine. [3H]Bremazocine binds to twice as many naloxone-sensitive sites as other nonselective opioid agonists, as shown in four membrane types that have very different ratios of mu, delta, and kappa receptor types. [...

Recent studies in our laboratory have shown that in mice, low doses of morphine in combination with Delta(9)-tetrahydrocannabinol (Delta(9)-THC) have a similar antinociceptive effect to high doses of morphine alone. After short-term administration of this combination, there is no behavioral tolerance to the opioid. Previous binding studies and Western analyses following chronic morphine exposur...

BACKGROUND Intrathecal (IT) morphine given after a short interval of aortic occlusion in a rodent model induced transient spastic paraparesis via opioid receptor-predicted actions in spinal cord. To determine the role(s) of spinal opioid receptor subtypes we investigated whether IT administration of various selective opioid receptor agonists can induce paraparesis following a short period of sp...

This review is an attempt to highlight evidence that may implicate the endogenous opioid system in the pathogenesis of hypertension in humans. The evidence raised includes biochemical, physiological, pharmacological, and behavioral studies conducted in in vitro and in vivo systems, experimental models of hypertension, and humans with essential hypertension. While the compelling biochemical and ...