Anna Rizzi

Bio: Anna Rizzi is an academic researcher from University of Ferrara. The author has contributed to research in topics: Nociceptin receptor & NOP. The author has an hindex of 41, co-authored 99 publications receiving 5053 citations. Previous affiliations of Anna Rizzi include Université de Sherbrooke.

Pharmacology of nociceptin and its receptor: a novel therapeutic target

Abstract: Nociceptin (NC), alias Orphanin FQ, has been recently identified as the endogenous ligand of the opioid receptor-like 1 receptor (OP4). This new NC/OP4 receptor system belongs to the opioid family and has been characterized pharmacologically with functional and binding assays on native (mouse, rat, guinea-pig) and recombinant (human) receptors, by using specific and selective agonists (NC, NC(1–13)NH2) and a pure and competitive antagonist, [Nphe1]NC(1–13)NH2. The similar order of potency of agonists and affinity values of the antagonist indicate that the same receptor is present in the four species. OP4 is expressed in neurons, where it reduces activation of adenylyl cyclase and Ca2+ channels while activating K+ channels in a manner similar to opioids. In this way, OP4 mediates inhibitory effects in the autonomic nervous system, but its activities in the central nervous system can be either similar or opposite to those of opioids. In vivo experiments have demonstrated that NC modulates a variety of biological functions ranging from nociception to food intake, from memory processes to cardiovascular and renal functions, from spontaneous locomotor activity to gastrointestinal motility, from anxiety to the control of neurotransmitter release at peripheral and central sites. These actions have been demonstrated using NC and various pharmacological tools, as antisense oligonucleotides targeting OP4 or the peptide precursor genes, antibodies against NC, an OP4 receptor selective antagonist and with data obtained from animals in which the receptor or the peptide precursor genes were knocked out. These new advances have contributed to better understanding of the pathophysiological role of the NC/OP4 system, and ultimately will help to identify the therapeutic potential of new OP4 receptor ligands.

A new selective antagonist of the nociceptin receptor

Abstract: [Phe1Ψ(CH2-NH)Gly2]NC(1-13)NH2 has been tested in the electrically stimulated guinea pig ileum and mouse vas deferens, two nociceptin sensitive preparations. The new compound showed per se little or no effect in the two tissues, but it displaced to the right the concentration-response curves of nociceptin in a concentration-dependent manner. Schild analyses of the data indicated a competitive type of antagonism and pA2 values of 7.02 and 6.75 in the guinea-pig ileum and the mouse vas deferens, respectively. At 10 μM [Phe1Ψ(CH2-NH)Gly2]NC(1-13)NH2 does not modify either the inhibitory effect of deltorphin I (the selective δ opioid receptor agonist) in the mouse vas deferens or that of dermorphine (the selective μ opioid receptor agonist) in the guinea-pig ileum. The present findings indicate that [Phe1Ψ(CH2-NH)Gly2]NC(1-13)NH2 is a selective antagonist of the nociceptin receptor. British Journal of Pharmacology (1998) 123, 163–165; doi:10.1038/sj.bjp.0701640

Characterization of [Nphe1]nociceptin(1-13)NH2, a new selective nociceptin receptor antagonist

Abstract: Nociceptin (orphanin FQ) is a novel neuropeptide capable of inducing a variety of biological actions via activation of a specific G-protein coupled receptor However, the lack of a selective nociceptin receptor antagonist has hampered our understanding of nociceptin actions and the role of this peptide in pathophysiological states As part of a broader programme of research, geared to the identification and characterization of nociceptin receptor ligands, we report that the novel peptide [Nphe1]nociceptin(1-13)NH2 acts as the first truly selective and competitive nociceptin receptor antagonist and is devoid of any residual agonist activity [Nphe1]nociceptin(1-13)NH2 binds selectively to recombinant nociceptin receptors expressed in Chinese hamster ovary (CHO) cells (pKi 84) and competitively antagonizes the inhibitory effects of nociceptin (i) on cyclic AMP accumulation in CHO cells (pA2 60) and (ii) on electrically evoked contractions in isolated tissues of the mouse, rat and guinea-pig with pA2 values ranging from 60 to 64 [Nphe1]nociceptin(1-13)NH2 is also active in vivo, where it prevents the pronociceptive and antimorphine actions of intracerebroventricularly applied nociceptin, measured in the mouse tail withdrawal assay Moreover, [Nphe1]nociceptin(1-13)NH2 produces per se a dose dependent, naloxone resistant antinociceptive action and, at relatively low doses, potentiates morphine-induced analgesia Collectively our data indicate that [Nphe1]nociceptin(1-13)NH2, acting as a nociceptin receptor antagonist, may be the prototype of a new class of analgesics British Journal of Pharmacology (2000) 129, 1183–1193; doi:101038/sjbjp0703169

Neuropeptide S is a stimulatory anxiolytic agent: a behavioural study in mice

Abstract: Background and purpose: Neuropeptide S (NPS) was recently identified as the endogenous ligand of an orphan receptor, now referred to as the NPS receptor. In vivo, NPS produces a unique behavioural profile by increasing wakefulness and exerting anxiolytic-like effects. In the present study, we further evaluated the effects of in vivo supraspinal NPS in mice. Experimental approach: Effects of NPS, injected intracerebroventricularly (i.c.v.), on locomotor activity (LA), righting reflex (RR) recovery and on anxiety states (measured with the elevated plus maze (EPM) and stress-induced hyperthermia (SIH) tests) were assessed in Swiss mice. Key results: NPS (0.01–1 nmol per mouse) caused a significant increase in LA in naive mice, in mice habituated to the test cages and in animals sedated with diazepam (5 mg kg−1). In the RR assay, NPS dose dependently reduced the proportion of animals losing the RR in response to diazepam (15 mg kg−1) and their sleeping time. In the EPM and SIH test, NPS dose dependently evoked anxiolytic-like effects by increasing the time spent by animals in the open arms and reducing the SIH response, respectively. Conclusions and implications: We provide further evidence that NPS acts as a novel modulator of arousal and anxiety-related behaviours by promoting a unique pattern of effects: stimulation associated with anxiolysis. Therefore, NPS receptor ligands may represent innovative drugs for the treatment of sleep and anxiety disorders. British Journal of Pharmacology (2008) 154, 471–479; doi:10.1038/bjp.2008.96; published online 31 March 2008

Physiology of Microglia

Abstract: Microglial cells are the resident macrophages in the central nervous system. These cells of mesodermal/mesenchymal origin migrate into all regions of the central nervous system, disseminate through the brain parenchyma, and acquire a specific ramified morphological phenotype termed "resting microglia." Recent studies indicate that even in the normal brain, microglia have highly motile processes by which they scan their territorial domains. By a large number of signaling pathways they can communicate with macroglial cells and neurons and with cells of the immune system. Likewise, microglial cells express receptors classically described for brain-specific communication such as neurotransmitter receptors and those first discovered as immune cell-specific such as for cytokines. Microglial cells are considered the most susceptible sensors of brain pathology. Upon any detection of signs for brain lesions or nervous system dysfunction, microglial cells undergo a complex, multistage activation process that converts them into the "activated microglial cell." This cell form has the capacity to release a large number of substances that can act detrimental or beneficial for the surrounding cells. Activated microglial cells can migrate to the site of injury, proliferate, and phagocytose cells and cellular compartments.

International Union of Pharmacology. XLV. Classification of the Kinin Receptor Family: from Molecular Mechanisms to Pathophysiological Consequences

Abstract: Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.