Sex differences in the experience of clinical and experimental pain have been reported. However, the neurobiological sources underlying the variability in pain responses between sexes have not been adequately explored, especially in humans. The endogenous opioid neurotransmitters and mu-opioid receptors are centrally implicated in responses to stress, in the suppression of pain, and in the acti...

Mu opioid receptors are present throughout the central and peripheral nervous systems. Peripheral inflammation causes an increase in mu receptor levels on peripheral terminals of primary afferent neurons. Recent studies indicate that activation of peripheral mu receptors produces antihyperalgesic effects in animals and humans. Here, we describe the in vitro pharmacological and in vivo pharmacok...

We have examined the endocytic trafficking of epitope-tagged delta and mu opioid receptors expressed in human embryonic kidney (HEK) 293 cells. These receptors are activated by peptide agonists (enkephalins) as well as by the alkaloid agonist drugs etorphine and morphine. Enkephalins and etorphine cause opioid receptors to internalize rapidly (t1/2 approximately 6 min) by a mechanism similar to...

Introduction: Genes often have multiple polymorphisms that interact with each other and the environment in different individuals. Variability in the opioid receptors can influence opiate withdrawal and dependence. In humans, A118G Single Nucleotide Polymorphisms (SNP) on μ-Opioid Receptor (MOR), 36 G>T in κ-Opioid Receptor (KOR), and T921C in the δ-Opioid Receptor (DOR) have been...

Introduction: There is a major societal need for analgesics with less tolerance, dependence, and abuse liability. Preclinical rodent studies suggest that bifunctional ligands both mu (MOPr) delta (DOPr) opioid peptide receptor activity may produce analgesia reduced tolerance other side effects. This study explores the structure-activity relationships (SAR) of our previously reported MOPr/DOPr l...

Mu- and delta-opioid subtype receptor antagonists were tested in the mouse for their effects on vertical climbing activity, an index of striatal dopaminergic activity. The selective delta-opioid antagonist ICI 154 129 (I/l) by itself enhanced vertical climbing activity in a dose-related manner, whereas the mu-opioid antagonist naloxone by itself was inactive on climbing behavior. Naloxone incre...

The inhibition of hippocampal pyramidal cells occurs via inhibitory interneurons making GABAergic synapses on distinct segments of the postsynaptic membrane. In area CA1 of the hippocampus, the activation of mu- and delta-opioid receptors inhibits these interneurons, thereby increasing the excitability of the pyramidal cells. Through the use of selective opioid agonists and biocytin-filled whol...

Systemic administration of resiniferatoxin (RTX), an ultrapotent capsaicin analogue, removes transient receptor potential vanilloid type 1 (TRPV1)-expressing afferent neurons and impairs thermal but not mechanical nociception in adult animals. In this study, we determined how loss of TRPV1-expressing sensory neurons alters the antinociceptive effect of mu opioids and mu opioid receptors in the ...

References 1. Carpenter KH, Wiley V. Application of tandem mass spectrometry to biochemical genetics and newborn screening. Clin Chim Acta 2002;322:1–10. 2. Carreiro-Lewandowski E. Newborn screening: an overview. Clin Lab Sci 2002;15:229–30. 3. Jones PM, Bennett MJ. The changing face of newborn screening: diagnosis of inborn errors of metabolism by tandem mass spectrometry. Clin Chim Acta 2002;...

The parafascicular nucleus (PFN) of thalamus, as a supraspinal structure, has an important role in processing of nociceptive information. In addition, μ-opioid receptor contributes to supraspinal modulation of nociception. In the present study, the effects of microinjection of naloxone (a non-specific opioid-receptor antagonist) and naloxonazine (a specific μ-opioid receptor antagonist) were in...