The effects of highly selective mu and delta opioid peptide agonists were determined in two rat models of experimentally-induced convulsions, the flurothyl threshold test and the maximal electroshock test. Intracerebroventricular injections of the mu selective enkephalin DAGO (0.3-2.2 nmol) resulted in a dose-related protection in both seizure models. Pretreatment with a low dose of naloxone (2...

Chronic pruritus is frequently refractory to currently available treatments. Studies suggest that pruritus may arise from an imbalance of the mu- and kappa-opioid receptor system activity in either the skin or the central nervous system. Stimulation of kappa-opioid receptors by their agonists inhibits pruritus in both animals and humans. The antipruritic effect of kappa-opioid receptors agonist...

Dynorphin A is an endogenous opioid peptide that activates the kappa opioid receptor (KOR) with high potency. Some studies also showed that the distribution and functional activity of dynorphin A are not completely correlated with those of KOR, suggesting that dynorphin A may interact with other receptors. To investigate the possibility that dynorphin A may serve as an agonist for other opioid ...

Delta (DOR) and mu opioid receptors (MOR) can complex as heteromers, conferring functional properties in agonist binding, signaling and trafficking that can differ markedly from their homomeric counterparts. Because of these differences, DOR/MOR heteromers may be a novel therapeutic target in the treatment of pain. However, there are currently no ligands selective for DOR/MOR heteromers, and, c...

Two 14beta-p-nitrocinnamoyl derivatives of dihydrocodeinone, 14beta-(p-nitrocinnamoylamino)-7,8-dihydrocodeinone (CACO) and N-cyclopropylmethylnor-14beta-(p-nitrocinnamoylamino)- 7, 8-dihydrocodeinone (N-CPM-CACO), and the corresponding chlorocinnamoylamino analogs, 14beta-(p-chlorocinnamoylamino)-7, 8-dihydrocodeinone (CAM) and N-cyclopropylmethylnor-14beta-(p-chlorocinnamoylamino) -7, 8-dihyd...

The interactions between dopamine receptors and opioid receptors coupled to adenylate cyclase in rat neostriatum were investigated. cAMP efflux from neostriatal slices induced by simultaneous activation of (stimulatory) D-1 and (inhibitory) D-2 dopamine receptors with 30 microM dopamine was inhibited by the preferential delta-opioid receptor agonist [D-Ala2-D-Leu5] enkephalin (DADLE) and the mu...

Opioids/opiates are commonly administered to alleviate pain, unload the heart, or decrease breathlessness in patients with advanced heart failure. As such, it is important to evaluate whether the myocardial opioidergic system is altered in cardiac disease. A hamster model of spontaneous hypertension was investigated before the development of hypertension (1 mo of age) and in the hypertensive st...

Patients receiving opioids report feeling sleepy, but opioids actually inhibit the rapid eye movement phase of sleep (REM). Inhibition of REM sleep is followed by a rebound increase in REM sleep associated with cardiopulmonary complications. The medial pontine reticular formation (mPRF) is a brain region from which morphine can inhibit REM sleep. The present study tested the hypothesis that spe...

Pavlovian fear learning depends on predictive error, so that fear learning occurs when the actual outcome of a conditioning trial exceeds the expected outcome. Previous research has shown that opioid receptors, including mu-opioid receptors in the ventrolateral quadrant of the midbrain periaqueductal gray (vlPAG), mediate such predictive fear learning. Four experiments reported here used a with...