The present study was undertaken to assess if hypothalamic beta-endorphin (beta E) and/or brain mu opioid receptors are associated with 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) (50 micrograms/kg)-induced hypophagia and body weight decline in rats. Hypothalamic beta E concentrations were initially increased to 166% of controls on day 1, and then were depressed to 39% and 49% of control valu...

Prominent interindividual and sex-dependent differences have been described in responses to sustained pain and other stressful stimuli. Variations in mu-opioid receptor-mediated endogenous opioid neurotransmission may underlie some of these processes. We examined both baseline mu-opioid receptor levels and the activation of this neurotransmitter system during sustained pain using positron emiss...

The opioid receptor subtypes and brain regions involved in eliciting convulsions and wet dog shakes (WDS) were studied by testing different opioid receptor selective agonists in unanesthetized rats. Selective mu agonists, [NMe-Phe3-D-Pro4]-morphiceptin (PL017) and [D-Ala2-N-methyl-Phe3-Gly5-ol]-enkephalin, induced convulsions and WDS when unilaterally injected into the ventral hippocampus. [D-A...

Current therapy for inflammatory pain includes the peripheral application of opioid receptor agonists. Activation of opioid receptors modulates voltage-gated ion channels, but it is unclear whether opioids can also influence ligand-gated ion channels [e.g., the transient receptor potential vanilloid type 1 (TRPV1)]. TRPV1 channels are involved in the development of thermal hypersensitivity asso...

Opioid receptors have been shown to dimerize or oligomerize among themselves and each other, affecting their functional properties. This study used bioluminescence resonance energy transfer (BRET) between the mu, delta, and kappa opioid receptors to study opioid receptor aggregation in transfected human embryonic kidney 293 cells. Titration of receptor levels indicated that all three opioid rec...

This study examined the effects of intrathecally (i.t.) administered mu and delta opioid receptor agonists on the flinching behavior and the expression of Fos-like immunoreactivity (Fos-LI) in the spinal cord elicited by s.c. injection of 5% formalin in one hindpaw of the rat. Intrathecal pretreatment with either the delta-1 opioid receptor agonist [D-Pen2,5]enkephalin (DPDPE) or the delta-2 op...

Ultra-low-dose opioid antagonists enhance opioid analgesia and reduce analgesic tolerance and dependence by preventing a G protein coupling switch (Gi/o to Gs) by the mu opioid receptor (MOR), although the binding site of such ultra-low-dose opioid antagonists was previously unknown. Here we show that with approximately 200-fold higher affinity than for the mu opioid receptor, naloxone binds a ...

OBJECTIVE Both age and gender are being increasingly recognized as important factors influencing CNS structure and function. However, there are relatively few data on actual neurochemical differences between the sexes in human subjects or on their interaction with age. One of the central neurotransmitter systems for which sex differences have been suggested by animal models and clinical human d...

Slip-down from a raised platform was previously found in mice treated with morphine, and this behavior was also recognized in mice treated with a monoamine releaser methamphetamine. Pharmacological examination on the slip-down indicated that the behavior was induced by receptor stimulations by D2 agonist PPHT and 5HT-2 agonist DOI. In mice treated with PPHT, antagonists of D1, alpha2, 5HT-2 and...

The increase in opioidergic tone by the central administration of morphine, which binds to the mu opioid receptor, is associated with pruritus. Pruritus is a symptom of cholestasis, which appears to result, in part, from increased opioidergic tone; a central mechanism has been proposed. The single nucleotide polymorphism Al18G in exon 1 of the opioid receptor mu 1 (OPRM1) gene, which codes for ...