Role of Nociceptin/Orphanin FQ-NOP Receptor System in the Regulation of Stress-Related Disorders

Nociceptin/orphanin FQ (N/OFQ) is a 17-residue neuropeptide that binds the nociceptin opioid-like receptor (NOP). N/OFQ exhibits nucleotidic and aminoacidics sequence homology with the precursors of other opioid neuropeptides but it does not activate either MOP, KOP or DOP receptors. Furthermore, opioid neuropeptides do not activate the NOP receptor. Generally, activation of N/OFQ system exerts anti-opioids effects, for instance toward opioid-induced reward and analgesia. The NOP receptor is widely expressed throughout the brain, whereas N/OFQ localization is confined to brain nuclei that are involved in stress response such as amygdala, BNST and hypothalamus. Decades of studies have delineated the biological role of this system demonstrating its involvement in significant physiological processes such as pain, learning and memory, anxiety, depression, feeding, drug and alcohol dependence. This review discusses the role of this peptidergic system in the modulation of stress and stress-associated psychiatric disorders in particular drug addiction, mood, anxiety and food-related associated-disorders. Emerging preclinical evidence suggests that both NOP agonists and antagonists may represent a effective therapeutic approaches for substances use disorder. Moreover, the current literature suggests that NOP antagonists can be useful to treat depression and feeding-related diseases, such as obesity and binge eating behavior, whereas the activation of NOP receptor by agonists could be a promising tool for anxiety.

An opioid-like system regulating feeding behavior in C. elegans

Neuropeptides are essential for the regulation of appetite. Here we show that neuropeptides could regulate feeding in mutants that lack neurotransmission from the motor neurons that stimulate feeding muscles. We identified nlp-24 by an RNAi screen of 115 neuropeptide genes, testing whether they affected growth. NLP-24 peptides have a conserved YGGXX sequence, similar to mammalian opioid neuropeptides. In addition, morphine and naloxone respectively stimulated and inhibited feeding in starved worms, but not in worms lacking NPR-17, which encodes a protein with sequence similarity to opioid receptors. Opioid agonists activated heterologously expressed NPR-17, as did at least one NLP-24 peptide. Worms lacking the ASI neurons, which express npr-17, did not response to naloxone. Thus, we suggest that Caenorhabditis elegans has an endogenous opioid system that acts through NPR-17, and that opioids regulate feeding via ASI neurons. Together, these results suggest C. elegans may be the first genetically tractable invertebrate opioid model.

Amethystic agents influencing toxicodynamics of ethanol

The pathogenetic mechanisms of acute alcoholic intoxications are examined and is based the expediency of the search for the amethystic agents, which influence neurotransmitter systems. Promising should be considered the agents, which modulate GABA-systems (partial reverse agonists of benzodiazepine receptors), glutamate (antagonists of metabotropic receptors mGluR2/3), opioid neuropeptides (antagonists of opioid receptors), acetylcholine (reversible inhibitors of acetylcholinesterase and M-cholinoagonists), adenosine (selective antagonists of A -receptors). The amethystic effect manifest also the substances, which modify the second messengers systems (calcium, nitrergic and cascade of arachidonic acid). The most of the means examined possesses the moderate amethystic potential, and effectiveness is manifested predominantly during the preventive application.

Neuropeptide mimetics for pain management

The discovery of numerous endogenous neuropeptides that participate in the formation, transmission, modulation, and perception of pain signals offers numerous strategies for the development of new analgesics. Nevertheless, the same research has not yet replaced opioids as the gold standard of pain treatment. Therefore, one possible avenue of drug development may shift interest from searching for receptor-selective opioids to creating an arsenal of drugs that target multiple opioid and non-opioid sites simultaneously. The presented short review focuses on the development of potential analgesic peptidomimetic compounds based upon opioid neuropeptides and substance P.