Gamma-aminobutyric acid (GABA)-containing interneurons of the ventral tegmental area (VTA) regulate the activity of dopaminergic neurons. These GABAergic interneurons are known to be innervated by synaptic terminals containing enkephalin, an endogenous ligand of mu-opioid receptors. Bath application of mu-opioid receptor agonists inhibits the activity of VTA GABAergic neurons but the mechanism ...

Mitragynine is an indole alkaloid isolated from the Thai medicinal plant Mitragyna speciosa. We previously reported the morphine-like action of mitragynine and its related compounds in the in vitro assays. In the present study, we investigated the opioid effects of 7-hydroxymitragynine, which is isolated as its novel constituent, on contraction of isolated ileum, binding of the specific ligands...

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. [...

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 ...

Extensive evidence demonstrates functional interactions between the adrenergic and opioid systems in a diversity of tissues and organs. While some effects are due to receptor and second messenger cross-talk, recent research has revealed an extracellular, allosteric opioid binding site on adrenergic receptors that enhances adrenergic activity and its duration. The present research addresses whet...

The endogenous opioid system, comprised of multiple opioid neuropeptide and receptor gene families, is highly expressed by developing neural cells and can significantly influence neuronal and glial maturation. In many central nervous system (CNS) regions, the expression of opioid peptides and receptors occurs only transiently during development, effectively disappearing with subsequent maturati...

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 ...

Introduction:The hippocampus is one for the major centers of learning and memory. Role of the opioid system has been investigated and on the other hand receptors related to this system such as mu-opioid receptors (MOR) are extended in the hippocampus. In this study the effect of Naloxone administration as a mu opioid receptor antagonist on passive avoidance memory in adult male rats was i...

objective: strong evidence indicate that activity of glucocorticoid receptors is necessary for emotional memory processess and these effects probably are mediated by hipppocampal opioid receptors. the aim of this study was to test whether there were any interaction between glucocorticoid and hippocampal opiate receptors on consolidtaion and retrieval of spatial memory. materials and methods: in...

Opium and its derivatives are potent analgesics that also have many other pharmacological effects in the nervous system. These agents and the endogenous opioid peptides exert their effects by interacting with high-affinity receptors. Complementary DNAs encoding the delta, kappa and mu opioid receptors have been isolated and characterized. These receptors, which are members of the superfamily of...