Role of bradykinin B(1) receptors in diabetes-induced hyperalgesia in streptozotocin-treated mice

Peptides Isolated from Amphibian Skin Secretions with Emphasis on Antimicrobial Peptides

The skin of amphibians is a tissue with biological functions, such as defense, respiration, and excretion. In recent years, researchers have discovered a large number of peptides in the skin secretions of amphibians, including antimicrobial peptides, antioxidant peptides, bradykinins, insulin-releasing peptides, and other peptides. This review focuses on the origin, primary structure, secondary structure, length, and functions of peptides secreted from amphibians' skin. We hope that this review will provide further information and promote the further study of amphibian skin secretions, in order to provide reference for expanding the research and application of amphibian bioactive peptides.

HumanMine: advanced data searching, analysis and cross-species comparison

HumanMine (www.humanmine.org) is an integrated database of human genomics and proteomics data that provides a powerful interface to support sophisticated exploration and analysis of data compiled from experimental, computational and curated data sources. Built using the InterMine data integration platform, HumanMine includes genes, proteins, pathways, expression levels, Single nucleotide polymorphism (SNP), diseases and more, integrated into a single searchable database. HumanMine promotes integrative analysis, a powerful approach in modern biology that allows many sources of evidence to be analysed together. The data can be accessed through a user-friendly web interface as well as a powerful, scriptable web service Application programming interface (API) to allow programmatic access to data. The web interface includes a useful identifier resolution system, sophisticated query options and interactive results tables that enable powerful exploration of data, including data summaries, filtering, browsing and export. A set of graphical analysis tools provide a rich environment for data exploration including statistical enrichment of sets of genes or other biological entities. HumanMine can be used for integrative multistaged analysis that can lead to new insights and uncover previously unknown relationships.

Database URL: https://www.humanmine.org

Depolarizing Effectors of Bradykinin Signaling in Nociceptor Excitation in Pain Perception

Inflammation is one of the main causes of pathologic pain. Knowledge of the molecular links between inflammatory signals and pain-mediating neuronal signals is essential for understanding the mechanisms behind pain exacerbation. Some inflammatory mediators directly modulate the excitability of pain-mediating neurons by contacting the receptor molecules expressed in those neurons. For decades, many discoveries have accumulated regarding intraneuronal signals from receptor activation through electrical depolarization for bradykinin, a major inflammatory mediator that is able to both excite and sensitize pain-mediating nociceptor neurons. Here, we focus on the final effectors of depolarization, the neuronal ion channels, whose functionalities are specifically affected by bradykinin stimulation. Particular G-protein coupled signaling cascades specialized for each specific depolarizer ion channels are summarized. Some of these ion channels not only serve as downstream effectors but also play critical roles in relaying specific pain modalities such as thermal or mechanical pain. Accordingly, specific pain phenotypes altered by bradykinin stimulation are also discussed. Some members of the effector ion channels are both activated and sensitized by bradykinin-induced neuronal signaling, while others only sensitized or inhibited, which are also introduced. The present overview of the effect of bradykinin on nociceptor neuronal excitability at the molecular level may contribute to better understanding of an important aspect of inflammatory pain and help future design of further research on the components involved and pain modulating strategies.

Potentiation of Paclitaxel-Induced Pain Syndrome in Mice by Angiotensin I Converting Enzyme Inhibition and Involvement of Kinins

Paclitaxel is a chemotherapeutic agent used to treat solid tumours. However, it causes an acute and neuropathic pain syndrome that limits its use. Among the mechanisms involved in neuropathic pain caused by paclitaxel is activation of kinin receptors. Angiotensin converting enzyme (ACE) inhibitors can enhance kinin receptor signalling. The goal of this study was to evaluate the role of kinins on paclitaxel-associated acute pain syndromes (P-APS) and the effect of ACE inhibition on P-APS and paclitaxel-associated chronic peripheral neuropathy (P-CPN) in mice. Herein, we show that paclitaxel caused mechanical allodynia and spontaneous nociceptive behaviour that was reduced by antagonists of kinin receptors B₁ (DALBk and SSR240612) and B₂ (Hoe140 and FR173657). Moreover, enalapril (an ACE inhibitor) enhanced the mechanical allodynia induced by a low dose of paclitaxel. Likewise, paclitaxel injection inhibited ACE activity and increased the expressions of B₁ and B₂ receptors and bradykinin-related peptides levels in peripheral tissue. Together, our data support the involvement of kinin receptors in the P-APS and suggest kinin receptor antagonists to treat this syndrome. Because hypertension is the most frequent comorbidity affecting cancer patients, treatment of hypertension with ACE inhibitors in patients undergoing paclitaxel chemotherapy should be reviewed, since this could enhance the P-APS and P-CPN.

Neuropeptides: metabolism to bioactive fragments and the pharmacology of their receptors

The proteolytic processing of neuropeptides has an important regulatory function and the peptide fragments resulting from the enzymatic degradation often exert essential physiological roles. The proteolytic processing generates, not only biologically inactive fragments, but also bioactive fragments that modulate or even counteract the response of their parent peptides. Frequently, these peptide fragments interact with receptors that are not recognized by the parent peptides. This review discusses tachykinins, opioid peptides, angiotensins, bradykinins, and neuropeptide Y that are present in the central nervous system and their processing to bioactive degradation products. These well-known neuropeptide systems have been selected since they provide illustrative examples that proteolytic degradation of parent peptides can lead to bioactive metabolites with different biological activities as compared to their parent peptides. For example, substance P, dynorphin A, angiotensin I and II, bradykinin, and neuropeptide Y are all degraded to bioactive fragments with pharmacological profiles that differ considerably from those of the parent peptides. The review discusses a selection of the large number of drug-like molecules that act as agonists or antagonists at receptors of neuropeptides. It focuses in particular on the efforts to identify selective drug-like agonists and antagonists mimicking the effects of the endogenous peptide fragments formed. As exemplified in this review, many common neuropeptides are degraded to a variety of smaller fragments but many of the fragments generated have not yet been examined in detail with regard to their potential biological activities. Since these bioactive fragments contain a small number of amino acid residues, they provide an ideal starting point for the development of drug-like substances with ability to mimic the effects of the degradation products. Thus, these substances could provide a rich source of new pharmaceuticals. However, as discussed herein relatively few examples have so far been disclosed of successful attempts to create bioavailable, drug-like agonists or antagonists, starting from the structure of endogenous peptide fragments and applying procedures relying on stepwise manipulations and simplifications of the peptide structures.

Preclinical pharmacology, metabolic stability, pharmacokinetics and toxicology of the peptidic kinin B1 receptor antagonist R-954

We previously showed that R-954 (AcOrn[Oic(2),(αMe)Phe(5),dβNal(7),Ile(8)]desArg(9)-bradykinin) is a potent, selective and stable peptide antagonist of the inducible GPCR kinin B1 receptor. This compound shows potential applications for the treatment of several diseases, including cancer and neurological disturbances of diabetes. To enable clinical translation, more information regarding its pharmacological, pharmacokinetics (PK) and toxicological properties at preclinical stage is warranted. This was the principal objective of the present study. Herein, specificity of R-954 was characterized in binding studies on 133 human molecular targets to reveal minor cross-reactivities against the angiotensin AT2 and the bombesin receptors (110- and 330-fold lower affinity than for B1R, respectively). The pharmacokinetic of R-954 was studied in both normal and streptozotocin-diabetic anaesthetized rats providing half-lives of 1.9-2.7h. R-954 does not appear to be metabolized in the rat circulation and in several rat tissue homogenates, as the kidney, lung and liver. It appears to be excreted as parent drug in the bile (21%) and in urine. A preliminary toxicological profile of R-954 was obtained in rats under various administration routes. R-954 appears to be well tolerated. Overall, these results indicate that R-954 exhibits favorable preclinical pharmacological/PK characteristics and encouraging safety profiles, suitable for early studies in humans.

Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors

Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.

Anti-nociceptive effect of kinin B₁ and B₂ receptor antagonists on peripheral neuropathy induced by paclitaxel in mice

BACKGROUND AND PURPOSE

In the current study, we investigated the role of both kinin B₁ and B₂ receptors in peripheral neuropathy induced by the chronic treatment of mice with paclitaxel a widely used chemotherapeutic agent.

EXPERIMENTAL APPROACH

Chemotherapy-evoked hyperalgesia was induced by i.p. injections of paclitaxel (2 mg·kg⁻¹) over 5 consecutive days. Mechanical and thermal hyperalgesia were evaluated between 7 and 21 days after the first paclitaxel treatment.

KEY RESULTS

Treatment with paclitaxel increased both mechanical and thermal hyperalgesia in mice (C57BL/6 and CD1 strains). Kinin receptor deficient mice (B₁, or B₂ receptor knock-out and B₁B₂ receptor, double knock-out) presented a significant reduction in paclitaxel-induced hypernociceptive responses in comparison to wild-type animals. Treatment of CD1 mice with kinin receptor antagonists (DALBK for B₁ or Hoe 140 for B₂ receptors) significantly inhibited both mechanical and thermal hyperalgesia when tested at 7 and 14 days after the first paclitaxel injection. DALBK and Hoe 140 were also effective against paclitaxel-induced peripheral neuropathy when given intrathecally or i.c.v. A marked increase in B₁ receptor mRNA was observed in the mouse thalamus, parietal and pre-frontal cortex from 7 days after the first paclitaxel treatment.

CONCLUSIONS AND IMPLICATIONS

Kinins acting on both B₁ and B₂ receptors, expressed in spinal and supra-spinal sites, played a crucial role in controlling the hypernociceptive state caused by chronic treatment with paclitaxel.

From bradykinin B2 receptor antagonists to orally active and selective bradykinin B1 receptor antagonists

The bradykinin (BK) B1 receptor is an attractive target for the treatment of chronic pain and inflammation. Starting from a dual B1 and B2 antagonist, novel antagonists were designed that display low-nanomolar affinity for human B1 receptor and selectivity over B2. Initially, potent imidazoline derivatives were studied, but these compounds suffered from low bioavailability. This issue could be overcome by the use of less basic amino derivatives leading to orally active compounds.

Osteoporosis in diabetes mellitus: Possible cellular and molecular mechanisms

Osteoporosis, a global age-related health problem in both male and female elderly, insidiously deteriorates the microstructure of bone, particularly at trabecular sites, such as vertebrae, ribs and hips, culminating in fragility fractures, pain and disability. Although osteoporosis is normally associated with senescence and estrogen deficiency, diabetes mellitus (DM), especially type 1 DM, also contributes to and/or aggravates bone loss in osteoporotic patients. This topic highlight article focuses on DM-induced osteoporosis and DM/osteoporosis comorbidity, covering alterations in bone metabolism as well as factors regulating bone growth under diabetic conditions including, insulin, insulin-like growth factor-1 and angiogenesis. Cellular and molecular mechanisms of DM-related bone loss are also discussed. This information provides a foundation for the better understanding of diabetic complications and for development of early screening and prevention of osteoporosis in diabetic patients.

Involvement of the cannabimimetic compound, N-palmitoyl-ethanolamine, in inflammatory and neuropathic conditions: review of the available pre-clinical data, and first human studies

The endogenous cannabimimetic compound, and anandamide analogue, N-palmitoyl-ethanolamine (PEA), was shown to exert potent anti-inflammatory and analgesic effects in experimental models of visceral, neuropathic and inflammatory pain by acting via several possible mechanisms. However, only scant data have been reported on the regulation of PEA levels during pathological conditions in animals or, particularly, humans. We review the current literature on PEA and report the results of three separate studies indicating that its concentrations are significantly increased during three different inflammatory and neuropathic conditions, two of which have been assessed in humans, and one in a mouse model. In patients affected with chronic low back pain, blood PEA levels were not significantly different from those of healthy volunteers, but were significantly and differentially increased (1.6-fold, P<0.01, N=10 per group) 30 min following an osteopathic manipulative treatment. In the second study, the paw skin levels of PEA in mice with streptozotocin-induced diabetic neuropathic pain were found to be significantly higher (1.5-fold, P<0.005, N=5) than those of control mice. In the third study, colonic PEA levels in biopsies from patients with ulcerative colitis were found to be 1.8-fold higher (P<0.05, N=8-10) than those in healthy subjects. These heterogeneous data, together with previous findings reviewed here, substantiate the hypothesis that PEA is an endogenous mediator whose levels are increased following neuroinflammatory or neuropathic conditions in both animals and humans, possibly to exert a local anti-inflammatory and analgesic action.

Cellular localization of kinin B1 receptor in the spinal cord of streptozotocin-diabetic rats with a fluorescent [Nalpha-Bodipy]-des-Arg9-bradykinin

Background

The kinin B₁ receptor (B₁R) is upregulated by pro-inflammatory cytokines, bacterial endotoxins and hyperglycaemia-induced oxidative stress. In animal models of diabetes, it contributes to pain polyneuropathy. This study aims at defining the cellular localization of B₁R in thoracic spinal cord of type 1 diabetic rats by confocal microscopy with the use of a fluorescent agonist, [Nα-Bodipy]-des-Arg⁹-BK (BdABK) and selective antibodies.

Methods

Diabetes was induced by streptozotocin (STZ; 65 mg/kg, i.p.). Four days post-STZ treatment, B₁R expression was confirmed by quantitative real-time PCR and autoradiography. The B₁R selectivity of BdABK was determined by assessing its ability to displace B₁R [¹²⁵I]-HPP-desArg¹⁰-Hoe140 and B₂R [¹²⁵I]-HPP-Hoe 140 radioligands. The in vivo activity of BdABK was also evaluated on thermal hyperalgesia.

Results

B₁R was increased by 18-fold (mRNA) and 2.7-fold (binding sites) in the thoracic spinal cord of STZ-treated rats when compared to control. BdABK failed to displace the B₂R radioligand but displaced the B₁R radioligand (IC₅₀ = 5.3 nM). In comparison, IC₅₀ values of B₁R selective antagonist R-715 and B₁R agonist des-Arg⁹-BK were 4.3 nM and 19 nM, respectively. Intraperitoneal BdABK and des-Arg⁹-BK elicited dose-dependent thermal hyperalgesia in STZ-treated rats but not in control rats. The B₁R fluorescent agonist was co-localized with immunomarkers of microglia, astrocytes and sensory C fibers in the spinal cord of STZ-treated rats.

Conclusion

The induction and up-regulation of B₁R in glial and sensory cells of the spinal cord in STZ-diabetic rats reinforce the idea that kinin B₁R is an important target for drug development in pain processes.

Neuropathic pain-like behavior after brachial plexus avulsion in mice: the relevance of kinin B1 and B2 receptors

The relevance of kinin B(1) (B(1)R) and B(2) (B(2)R) receptors in the brachial plexus avulsion (BPA) model was evaluated in mice, by means of genetic and pharmacological tools. BPA-induced hypernociception was absent in B(1)R, but not in B(2)R, knock-out mice. Local or intraperitoneal administration of the B(2)R antagonist Hoe 140 failed to affect BPA-induced mechanical hypernociception. Interestingly, local or intraperitoneal treatment with B(1)R antagonists, R-715 or SSR240612, dosed at the time of surgery, significantly reduced BPA-evoked mechanical hypernociception. Intrathecal or intracerebroventricular administration of these antagonists, at the surgery moment, did not prevent the hypernociception. Both antagonists, dosed by intraperitoneal or intrathecal routes (but not intracerebroventricularly) 4 d after the surgery, significantly inhibited the mechanical hypernociception. At 30 d after the BPA, only the intracerebroventricular treatment effectively reduced the hypernociception. A marked increase in B(1)R mRNA was observed in the hypothalamus, hippocampus, thalamus, and cortex at 4 d after BPA and only in the hypothalamus and cortex at 30 d. In the spinal cord, a slight increase in B(1)R mRNA expression was observed as early as at 2 d. Finally, an enhancement of B(1)R protein expression was found in all the analyzed brain structures at 4 and 30 d after the BPA, whereas in the spinal cord, this parameter was augmented only at 4 d. The data provide new evidence on the role of peripheral and central kinin B(1)R in the BPA model of neuropathic pain. Selective B(1)R antagonists might well represent valuable tools for the management of neuropathic pain.

Criteria for creating and assessing mouse models of diabetic neuropathy

Diabetic neuropathy (DN) is a serious and debilitating complication of both type 1 and type 2 diabetes. Despite intense research efforts into multiple aspects of this complication, including both vascular and neuronal metabolic derangements, the only treatment remains maintenance of euglycemia. Basic research into the mechanisms responsible for DN relies on using the most appropriate animal model. The advent of genetic manipulation has moved mouse models of human disease to the forefront. The ability to insert or delete genes affected in human patients offers unique insight into disease processes; however, mice are still not humans and difficulties remain in interpreting data derived from these animals. A number of studies have investigated and described DN in mice but it is difficult to compare these studies with each other or with human DN due to experimental differences including background strain, type of diabetes, method of induction and duration of diabetes, animal age and gender. This review describes currently used DN animal models. We followed a standardized diabetes induction protocol and designed and implemented a set of phenotyping parameters to classify the development and severity of DN. By applying standard protocols, we hope to facilitate the comparison and characterization of DN across different background strains in the hope of discovering the most human like model in which to test potential therapies.

The kallikrein-kinin system: current and future pharmacological targets

The kallikrein-kinin system is an endogenous metabolic cascade, triggering of which results in the release of vasoactive kinins (bradykinin-related peptides). This complex system includes the precursors of kinins known as kininogens and mainly tissue and plasma kallikreins. The pharmacologically active kinins, which are often considered as either proinflammatory or cardioprotective, are implicated in many physiological and pathological processes. The interest of the various components of this multi-protein system is explained in part by the multiplicity of its pharmacological activities, mediated not only by kinins and their receptors, but also by their precursors and their activators and the metallopeptidases and the antiproteases that limit their activities. The regulation of this system by serpins and the wide distribution of the different constituents add to the complexity of this system, as well as its multiple relationships with other important metabolic pathways such as the renin-angiotensin, coagulation, or complement pathways. The purpose of this review is to summarize the main properties of this kallikrein-kinin system and to address the multiple pharmacological interventions that modulate the functions of this system, restraining its proinflammatory effects or potentiating its cardiovascular properties.

Reduced nerve injury-induced neuropathic pain in kinin B1 receptor knock-out mice

Injury to peripheral nerves often results in a persistent neuropathic pain condition that is characterized by spontaneous pain, allodynia, and hyperalgesia. Nerve injury is accompanied by a local inflammatory reaction in which nerve-associated and immune cells release several pronociceptive mediators. Kinin B1 receptors are rarely expressed in nontraumatized tissues, but they can be expressed after tissue injury. Because B1 receptors mediate chronic inflammatory painful processes, we studied their participation in neuropathic pain using receptor gene-deleted mice. In the absence of neuropathy, we found no difference in the paw-withdrawal responses to thermal or mechanical stimulation between B1 receptor knock-out mice and 129/J wild-type mice. Partial ligation of the sciatic nerve in the wild-type mouse produced a profound and long-lasting decrease in thermal and mechanical thresholds in the paw ipsilateral to nerve lesion. Threshold changed neither in the sham-operated animals nor in the paw contralateral to lesion. Ablation of the gene for the B1 receptor resulted in a significant reduction in early stages of mechanical allodynia and thermal hyperalgesia. Furthermore, systemic treatment with the B1 selective receptor antagonist des-Arg9-[Leu8]-bradykinin reduced the established mechanical allodynia observed 7-28 d after nerve lesion in wild-type mice. Partial sciatic nerve ligation induced an upregulation in B1 receptor mRNA in ipsilateral paw, sciatic nerve, and spinal cord of wild-type mice. Together, kinin B1 receptor activation seems to be essential to neuropathic pain development, suggesting that an oral-selective B1 receptor antagonist might have therapeutic potential in the management of chronic pain.

The kinin system mediates hyperalgesia through the inducible bradykinin B1 receptor subtype: evidence in various experimental animal models of type 1 and type 2 diabetic neuropathy

Both insulin-dependent (type 1) and insulin-independent (type 2) diabetes are complex disorders characterized by symptomatic glucose intolerance due to either defective insulin secretion, insulin action or both. Unchecked hyperglycemia leads to a series of complications among which is painful diabetic neuropathy, for which the kinin system has been implicated. Here, we review and compare the profile of several experimental models of type 1 and 2 diabetes (chemically induced versus gene-prone) and the incidence of diabetic neuropathy upon aging. We discuss the efficacy of selective antagonists of the inducible bradykinin B1 receptor (BKB1-R) subtype against hyperalgesia assessed by various nociceptive tests. In either gene-prone models of type 1 and 2 diabetes, the incidence of hyperalgesia mostly precedes the development of hyperglycemia. The administration of insulin, achieving euglycemia, does not reverse hyperalgesia. Treatment with a selective BKB1-R antagonist does not affect basal nociception in most normal control rats, whereas it induces a significant time- and dose-dependent attenuation of hyperalgesia, or even restores nociceptive responses, in experimental diabetic neuropathy models. Diabetic hyperalgesia is absent in streptozotocin-induced type 1 diabetic BKB1-R knockout mice. Thus, selective antagonism of the inducible BKB1-R subtype may constitute a novel and potential therapeutic approach for the treatment of painful diabetic neuropathy.

Humanizing mice: catching up with elusive B1 receptors

Bradykinin receptor activation plays an important role in pain arising following tissue inflammation, and recent studies have suggested that bradykinin B1 receptors in particular may be important in chronic pain related to arthritis and various neuropathies. The investigation of the function of the B1 receptors in vivo has been hampered by the lack of nonpeptide antagonists, and the development of such compounds made more difficult by the considerable species variation between human and rodent B1 receptors. In this issue, Fox and co-workers report the creation of a mouse that has had the human B1 gene inserted into the corresponding mouse locus, and they exploit this animal to study the effects of a novel, nonpeptide B1 receptor antagonist on measures of acute nociception and nociception following inflammation. By creating a platform that allows the study of human B1 receptors in vivo, these investigators have provided a tool to significantly advance the understanding of the kallikrein-kinin system in physiological and pathophysiological states.

Inhibition of Type 1 Diabetic Hyperalgesia in Streptozotocin-Induced Wistar versus Spontaneous Gene-Prone BB/Worchester Rats: Efficacy of a Selective Bradykinin B1Receptor Antagonist

Insulin-dependent type 1 diabetes (T1D) is linked to a series of complications, including painful diabetic neuropathy (PDN). Several neurovascular systems are activated in T1D, including the inducible bradykinin (BK) B1 receptor (BKB1-R) subtype. We assessed and compared the efficacy profile of a selective BKB1-R antagonist on hyperalgesia in 2 models of T1D: streptozotocin (STZ) chemically induced diabetic Wistar rats and spontaneous BioBreeding/Worchester diabetic-prone (BB/Wor-DP) rats. Nociception was measured using the hot plate test to determine thermal hyperalgesia. STZ diabetic rats developed maximal hyperalgesia (35% decrease in their hot plate reaction time) within a week and remained in such condition and degree for up to 4 weeks postinjection. BB/Wor-DP rats also developed hyperalgesia over time that preceded hyperglycemia, starting at the age of 6 weeks (9% decrease in the hot plate reaction time) and stabilizing over the age of 16 to 24 weeks to a maximum (60% decrease in the hot plate reaction time). Single, acute subcutaneous administration of the selective BKB1-R antagonist induced significant time- and dose-dependent attenuation of hyperalgesia in both STZ diabetic and BB/Wor-DP rats. Thus, selective antagonism of the inducible BKB1-R subtype may constitute a novel and potential therapeutic approach for the treatment of PDN.

Expression and distribution of kinin B1 receptor in the rat brain and alterations induced by diabetes in the model of streptozotocin

A role for kinin B1 receptors was suggested in the spinal cord and peripheral organs of streptozotocin (STZ)-diabetic rats. The present study aims at determining whether B1 receptors are also induced and over-expressed in the brain of STZ-rats at 2, 7, and 21 days post-treatment. This was addressed by in situ hybridization using the [35S]-UTPalphaS-labeled riboprobe and by in vitro autoradiography with the radioligand [125I]-HPP-des-Arg10-Hoe 140. In control rats, B1 receptor mRNA was found widely distributed in many brain regions. Low mRNA levels were found in thalamus and hypothalamus (7-12 nCi/g) while high mRNA signals were detected in cortical regions and hippocampus (18-29 nCi/g). In diabetic rats, B1 receptor mRNA was markedly increased in hippocampus, temporal/parietal cortices and amygdala at 2 and 7 days (+88 to +150%). Low densities of B1 receptor binding sites were detected in all analyzed regions in control rats (0.18-0.37 fmol/mg tissue). In diabetic rats, B1 receptor binding sites were significantly increased in hippocampus, amygdala, temporal/parietal, and perhinal/piriform cortices (+ 55 to + 165 %) at 7 days only. Results highlight an early but transient and reversible up-regulation of B1 receptors in specific brain regions of STZ-diabetic rats. This may offer the advantage of reducing putative central side effects with B1 receptor antagonists if used for the treatment of diabetic complications in the periphery.

Putative roles of kinin receptors in the therapeutic effects of angiotensin 1-converting enzyme inhibitors in diabetes mellitus

The role of endogenous kinins and their receptors in diabetes mellitus is being confirmed with the recent developments of molecular and genetic animal models. Compelling evidence suggests that the kinin B(2) receptor is organ-protective and partakes to the therapeutic effects of angiotensin 1-converting enzyme inhibitors (ACEI) and angiotensin AT(1) receptor antagonists. Benefits derive primarily from vasodilatory, antihypertensive, antiproliferative, antihypertrophic, antifibrotic, antithrombotic and antioxidant properties of kinin B(2) receptor activation. Mechanisms include the formation of nitric oxide and prostacyclin and the inhibition of NAD(P)H oxidase activity involving classical and novel signalling pathways. Kinin B(2) receptor also ameliorates insulin resistance by increasing glucose uptake and supply, and by inducing glucose transporter-4 translocation either directly or through phosphorylation of insulin receptor. The kinin B(1) receptor, which is induced by the cytokine network, growth factors and hyperglycaemia, mediates hyperalgesia, vascular hyperpermeability and leukocytes infiltration in diabetic animals. However, emerging data highlight reno- and cardio-protective effects mediated by kinin B(1) receptor under chronic ACEI therapy in diabetes mellitus. Thus, the Janus-faced of kinin receptors needs to be taken into account in future drug development. For instance, locally acting kinin B(1)/B(2) receptor agonists if used in a safe therapeutic window may represent a more rationale strategy in the prevention and management of diabetic complications. Because kinin B(2) receptor antagonists may further increase insulin resistance, the persisting dogma that restricts the development of kinin receptor analogues to antagonists (that is still relevant to abrogate pain and inflammation) needs to be revisited.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

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.

Depression and cardiovascular disease: a reciprocal relationship

Until relatively recently, depression has been considered a purely "mental" disorder and therefore in the natural domain of psychologists and psychiatrists. However, recent epidemiological studies have revealed that aging, physical and psychological stress, chronic pain, several metabolic disorders such as insulin resistance and established diabetes, alcoholism, inflammatory conditions, and vascular disorders such as arterial hypertension all may be associated with depression. The present review examines some of these depression-associated factors and the mechanisms by which they might give rise to vascular disorders such as atherosclerosis, microcirculation endothelial dysfunction, and interstitial disturbances leading to organ damage. A number of disorders involving the circulation can lead progressively and insidiously to large artery rigidity, remodeling of peripheral arteries, and alterations of the microcirculation of large blood vessels. Perturbations in vasa vasorum blood flow may contribute to atherogenesis, in addition to the influence of numerous cellular events involved in inflammation (tumor necrosis factor alpha, interleukin 1 beta, etc). Since Hans Selye first described the neuroendocrine cascade generated by experimentally induced stress half a century ago, phenomena such as the axonal release of neurotransmitters (including serotonin), accumulation of metabolites such as homocysteine, platelet-activating factor, and nitric oxide also have been implicated in the pathogenesis of depression. Moreover, vascular consequences of depression such as heart rate and pulse pressure variations may lead to endothelial dysfunction in critical microcirculation networks (cerebral, myocardial, and renal) and initiate physicochemical alterations in interstitial compartments adjacent to vital organs. The appropriate use of ambulatory monitoring of vascular parameters, such as heart rate and pulse pressure, and eventually, early identification of genetic and metabolic markers may prove helpful in the early detection of events preceding and predicting the clinical manifestations of depression.

Hyperalgesia in non-obese diabetic (NOD) mice: A role for the inducible bradykinin B1 receptor

Most studies performed to investigate the role of the inducible bradykinin B(1) receptor in the pathology and complications of type 1 diabetes have been carried out using the model of streptozotocin (STZ)-induced diabetes. The model of spontaneous autoimmune diabetes in non-obese diabetic (NOD) mice involves a long-term inflammatory process that closely resembles the human type 1 diabetes. In the present study, we aimed at establishing the correlation between the progress of diabetic hyperalgesia and the incidence of diabetes, as a function of age, in NOD mice. We also evaluated the implication of the bradykinin B(1) receptor, a receptor up-regulated during the inflammatory progress of diabetes, in the development of diabetic hyperalgesia in NOD mice. Female NOD mice were followed up from the 4th to the 32nd week of age for the incidence of diabetes. Only NOD mice with plasma glucose concentration >20 mmol/l were considered diabetic. The nociception was assessed using the hot plate and the tail immersion pain tests and the effect of acute and chronic administration of the selective bradykinin B(1) receptor agonist, desArg(9)bradykinin and its selective antagonists, R-715 (Ac-Lys-[D-beta Nal(7), Ile(8)]desArg(9)bradykinin) and R-954 (Ac-Orn-[Oic(2), alpha-MePhe(5), D-beta Nal(7), Ile(8)]desArg(9)bradykinin), on the development of diabetic hyperalgesia was studied. Diabetic NOD mice developed a significant time-dependent hyperalgesia, as measured in both tests, starting from the 8th week of age with the maximum effect observed over 16 to 20 weeks, whereas the incidence of diabetes in the tested NOD mice was only 40.16% at the age of 16 weeks and reached a maximum of 73.23% at the age 24 weeks. Both acute and chronic administration of desArg(9)bradykinin (400 microg/kg) markedly increased the hyperalgesic activity in diabetic NOD mice in the hot plate and tail immersion nociceptive tests. The selective bradykinin B(1) receptor antagonist R-715 (400 microg/kg) and its more potent and long acting analogue R-954 (200 microg/kg), administered in acute or chronic manner, significantly attenuated diabetic hyperalgesia in NOD mice in both thermal pain tests and restored nociceptive responses to values observed in control non-diabetic siblings. Our results bring the first evidence that the development of hyperalgesia in NOD mice, a model of spontaneous type 1 diabetes, precedes the occurrence of hyperglycemia and is mediated by the bradykinin B(1) receptor. It is suggested that bradykinin B(1) receptor antagonism could become a novel therapeutic approach to the treatment of diabetic neuropathic complications.

Effects of a selective bradykinin B1 receptor antagonist on increased plasma extravasation in streptozotocin-induced diabetic rats: Distinct vasculopathic profile of major key organs

Diffuse vasculopathy is a common feature of the morbidity and increased mortality associated with insulino-dependent type 1 diabetes. Increased vascular permeability leading to plasma extravasation occurs in surrounding tissues following endothelial dysfunction. Such micro- and macro-vascular complications develop over time and lead to oedema, hypertension, cardiomyopathy, renal failure (nephropathy) and other complications (neuropathy, retinopathy). In the present investigation, we studied the effect of a selective bradykinin B(1) receptor antagonist, R-954, on the enhanced vascular permeability in streptozotocin (STZ)-induced diabetic Wistar rats compared with age-matched controls. Plasma extravasation was determined using Evans blue dye in selected target tissues (left and right heart atria, ventricles, lung, abdominal and thoracic aortas, liver, spleen, renal cortex and medulla), at 1 and 4 weeks following STZ administration. The vascular permeability was significantly increased in the aortas, cortex, medulla, and spleen in 1-week STZ rats and remained elevated at 4 weeks of diabetes. Both atria showed an increased vascular permeability only after 4-week STZ-administration. R-954 (2 mg/kg, bolus, s.c.), given 2 h prior to Evans blue dye, to 1- and 4-week diabetic rats significantly inhibited (by 48-100%) plasma leakage in most tested tissues affected by diabetes with no effect in healthy rats. These results showed that the inducible bradykinin B(1) receptor subtype participates in the modulation of the vascular permeability in diabetic rats and suggest that selective bradykinin B(1) receptor antagonism could have a beneficial role in reducing diabetic vascular complications.

Absence of diabetic hyperalgesia in bradykinin B1 receptor-knockout mice

Experimental evidence has shown that the inducible bradykinin (BK) B1 receptor (BKB1-R) subtype is involved in the development of hyperalgesia associated with type 1 diabetes. Selective BKB1-R antagonists inhibited, whereas selective agonists increased the hyperalgesic activity in diabetic mice in thermal nociceptive tests. Here we evaluate the development of diabetic hyperalgesia in a BKB1-R-knockout (KO) genotype compared to wild-type (WT) mice. The BKB1-R-KO mice were backcrossed for 10 generations to C57BL/6 genetic background before use in the experiments. Diabetes was induced by streptozotocin (STZ) and thermal nociception was assessed by the hot plate and tail immersion tests. The hyperalgesia observed in wild type mice was totally absent in the BKB1-R-KO mice. Furthermore, the selective BKB1-R agonist, desArg9BK, significantly increased the hyperalgesic activity in diabetic WT mice but had no effect on nociceptive responses in diabetic BKB1-R-KO mice. Taken together, the results confirm the crucial role of the BKB1-R, upregulated alongside inflammatory diabetes, in the development of diabetes-induced hyperalgesia.

Bradykinin stimulates MMP-2 production in guinea pig tracheal smooth muscle cells

The implication of bradykinin (BK) receptors in the release of the matrix metalloproteinase-2 (MMP-2; gelatinase A) was studied in guinea pig tracheal smooth muscle cells (GP-TSMC). Bradykinin (10(-8)-10(-4) M) induced a time- and concentration-dependent upregulation of MMP-2 production from cultured GP-TSMC. Pretreatment of the GP-TSMC with the bradykinin B2 receptor (BKB2-R) antagonist Hpp-HOE-140 (Hpp-D-Arg0-Hyp3-Thi5-D-Tic7-Oic8-BK; 10(-8)-10(-4) M) significantly inhibited the BK-stimulated upregulation of MMP-2 in GP-TSMC in a concentration-related manner. Conversely, GP-TSMC pretreated with the selective bradykinin B1 receptor (BKB1-R) antagonist R-954 (Ac-Om[Oic2, alpha-MePhe5, D-betaNal7, Ile8]desArg9BK; 10(-8)-10(-4) M) did not show any change in the response to BK. Moreover, the selective BKB2-R agonist Lys0BK (kallidin; 10(-8)-10(-4) M) stimulated whereas the selective BKB1-R agonist desArg9BK (DBK; 10(-8)-10(-4) M) had no effect on MMP-2 release from GP-TSMC. Further, the nonselective cyclooxygenase (COX) enzyme inhibitor indomethacin (IND; 10(-5) M), the glucocorticosteroid dexamethasone (DEX; 1 ng/mL) and the protein synthesis inhibitors, cycloheximide (CHX; 10(-6) M) and actinomycin D (ACT-D; 10(-8) M) also inhibited BK-induced MMP-2 release from GP-TSMC. These results provide the first evidence for the involvement of BK in the release of MMP-2 from airway smooth muscle cells through activation of the BKB2-R. Such response is mostly mediated by the induction of COX and the subsequent production of endogenous prostaglandins (PGs). It could therefore be suggested that MMP-2 might play a role in the process of airway remodeling.

Autoradiographic distribution and alterations of kinin B2 receptors in the brain and spinal cord of streptozotocin-diabetic rats

This study investigates whether bradykinin (BK) B(2) receptor binding sites are increased in the brain and thoracic spinal cord of streptozotocin (STZ)-diabetic rats at 2, 7, and 21 days posttreatment by in vitro autoradiography with the radioligand [(125)I]HPP-Hoe 140. In control and diabetic rats, specific binding sites for B(2) receptors were detected in the brain and in various laminae of the spinal cord, predominantly in superficial laminae (K(d)=34 pM). In diabetic rats, B(2) receptor densities were significantly increased in lamina l of the dorsal horn (+35% at 7 and 21 days), spinal trigeminal nucleus (+70% at 7 and 21 days) and nucleus tractus solitarius (+100% at 2 and 7 days). B(2) receptor analogues D-Arg[Hyp(3),Thi(5),D-Tic(7),Oic(8)]-BK (Hoe 140), 3-(4 hydroxyphenyl)propionyl-Hoe 140 (HPP-Hoe 140), LF16-0687 mesylate ((2-Pyrrolidinecarboxamide, N-[3-[[4-aminoiminomethyl)benzoyl]amino]propyl]-1-[[2,4-dichoro-3-[[(2,4-dimethyl-8-quinolinyl)oxy]methyl]phenyl]sulfonyl]-(2S)-(9Cl)), and BK decreased binding of [(125)I]-HPP-Hoe 140 in the spinal dorsal horn, with K(i) values of 0.5, 1.5, 3.2, and 3.7 nM, respectively. These values were not significantly different in diabetic rats at 7 days (0.5 (Hoe 140), 0.7 (HPP-Hoe 140), 1.2 (BK), and 1.7 (LF16-0687) nM). While des-Arg(10)-Hoe 140 was three orders of magnitude less potent than Hoe 140, B(1) receptor agonist (des-Arg(9)-BK) and antagonist (AcLys[D-betaNal(7),Ile(8)]des-Arg(9)-BK, R-715) did not affect [(125)I]-HPP-Hoe 140 binding at 1 microM concentration. Data suggest a very discrete and temporal increase of B(2) receptor density (without affinity changes) in the spinal cord and hindbrain of STZ-diabetic rats. This contrasts with the early induction and over-expression of B(1) receptors reported in the brain and spinal cord of STZ-diabetic rats.

Kinin B1 receptors: key G-protein-coupled receptors and their role in inflammatory and painful processes

Kinins are a family of peptides implicated in several pathophysiological events. Most of their effects are likely mediated by the activation of two G-protein-coupled receptors: B(1) and B(2). Whereas B(2) receptors are constitutive entities, B(1) receptors behave as key inducible molecules that may be upregulated under some special circumstances. In this context, several recent reports have investigated the importance of B(1) receptor activation in certain disease models. Furthermore, research on B(1) receptors in the last years has been mainly focused in determining the mechanisms and pathways involved in the process of induction. This was essentially favoured by the advances obtained in molecular biology studies, as well as in the design of selective and stable peptide and nonpeptide kinin B(1) receptor antagonists. Likewise, development of kinin B(1) receptor knockout mice greatly helped to extend the evidence about the relevance of B(1) receptors during pathological states. In the present review, we attempted to remark the main advances achieved in the last 5 years about the participation of kinin B(1) receptors in painful and inflammatory disorders. We have also aimed to point out some groups of chronic diseases, such as diabetes, arthritis, cancer or neuropathic pain, in which the strategic development of nonpeptidic oral-available and selective B(1) receptor antagonists could have a potential relevant therapeutic interest.

Bradykinin receptor ligands: therapeutic perspectives

Kinins, which are produced by the action of kallikrein enzymes, are blood-derived local-acting peptides that have broad effects mediated by two related G-protein-coupled receptors termed the bradykinin receptors. The endogenous kallikrein-kinin system controls blood circulation and kidney function, and promotes inflammation and pain in pathological conditions, which has led to interest in developing modulators of bradykinin receptors as potential therapeutics. This review discusses recent progress in our understanding of the genetics, molecular biology and pathophysiology of kinins and their receptors, as well as developments in medicinal chemistry, which have brought us closer to therapeutic applications of kinin receptor ligands in various indications. The potential of kinin receptor antagonists as novel analgesic agents that do not result in tolerance or have a liability for abuse has attracted particular interest.

INGAP peptide improves nerve function and enhances regeneration in streptozotocin-induced diabetic C57BL/6 mice

INGAP peptide comprises the core active sequence of Islet Neogenesis Associated Protein (INGAP), a pancreatic cytokine that can induce new islet formation and restore euglycemia in diabetic rodents. The ability of INGAP peptide in vitro to enhance nerve growth from sensory ganglia suggests its potential utility in peripheral nerve disorders. In this study, INGAP peptide was administered alone or in combination with insulin to streptozotocin-induced diabetic mice exhibiting signs of peripheral neuropathy. Following a 2-wk treatment period, thermal hypoalgesia in diabetic mice was significantly improved in groups that received INGAP peptide, without development of hyperalgesia. Explanted dorsal root ganglia (DRG) from these groups showed enhanced nerve outgrowth and evidence of increased mitochondrial activity. Western blotting experiments revealed attenuation of neurofilament hyperphosphorylation, up-regulation of beta-tubulin and actin, and increased phosphorylation of the transcription factor STAT3 in DRG. These findings suggest that INGAP peptide can activate some of the signaling pathways implicated in nerve regeneration in sensory ganglia, thereby providing a means of improvement of nociceptive dysfunction in the peripheral nervous system.

SSR240612 [(2R)-2-[((3R)-3-(1,3-Benzodioxol-5-yl)-3-{[(6-methoxy-2-naphthyl)sulfonyl]amino}propanoyl)amino]-3-(4-{[2R,6S)-2,6-dimethylpiperidinyl]methyl}phenyl)-N-isopropyl-N-methylpropanamide Hydrochloride], a New Nonpeptide Antagonist of the Bradykinin B1 Receptor: Biochemical and Pharmacological Characterization

The biochemical and pharmacological properties of a novel non-peptide antagonist of the bradykinin (BK) B(1) receptor, SSR240612 [(2R)-2-[((3R)-3-(1,3-benzodioxol-5-yl)-3-[[(6-methoxy-2-naphthyl)sulfonyl]amino]propanoyl)amino]-3-(4-[[2R,6S)-2,6-dimethylpiperidinyl]methyl]phenyl)-N-isopropyl-N-methylpropanamide hydrochloride] were evaluated. SSR240612 inhibited the binding of [(3)H]Lys(0)-des-Arg(9)-BK to the B(1) receptor in human fibroblast MRC5 and to recombinant human B(1) receptor expressed in human embryonic kidney cells with inhibition constants (K(i)) of 0.48 and 0.73 nM, respectively. The compound selectivity for B(1) versus B(2) receptors was in the range of 500- to 1000-fold. SSR240612 inhibited Lys(0)-desAr(9)-BK (10 nM)-induced inositol monophosphate formation in human fibroblast MRC5, with an IC(50) of 1.9 nM. It also antagonized des-Arg(9)-BK-induced contractions of isolated rabbit aorta and mesenteric plexus of rat ileum with a pA(2) of 8.9 and 9.4, respectively. Antagonistic properties of SSR240612 were also demonstrated in vivo. SSR240612 inhibited des-Arg(9)-BK-induced paw edema in mice (3 and 10 mg/kg p.o. and 0.3 and 1 mg/kg i.p.). Moreover, SSR240612 reduced capsaicin-induced ear edema in mice (0.3, 3 and 30 mg/kg p.o.) and tissue destruction and neutrophil accumulation in the rat intestine following splanchnic artery occlusion/reperfusion (0.3 mg/kg i.v.). The compound also inhibited thermal hyperalgesia induced by UV irradiation (1 and 3 mg/kg p.o.) and the late phase of nociceptive response to formalin in rats (10 and 30 mg/kg p.o.). Finally, SSR240612 (20 and 30 mg/kg p.o.) prevented neuropathic thermal pain induced by sciatic nerve constriction in the rat. In conclusion, SSR240612 is a new, potent, and orally active specific non-peptide bradykinin B(1) receptor antagonist.

Des-Arg9-bradykinin increases intracellular Ca2+ in bronchoalveolar eosinophils from ovalbumin-sensitized and -challenged mice

The effects of the selective bradykinin B1 receptor agonist, des-Arg9-bradykinin and the bradykinin B2 receptor agonist, bradykinin were studied on the intracellular free Ca2+ concentration ([Ca2+]i) in murine bronchoalveolar lavage cells from control and ovalbumin-sensitized mice using fura-2 microfluorimetry. The bronchoalveolar lavage cells of control mice, which were predominantly alveolar macrophages, showed an increase in [Ca2+]i in response to bradykinin (1 microM) but not to des-Arg9-bradykinin (1 microM), indicating the presence of functional bradykinin B2 receptors and the absence of B1 receptors. Such elevation in [Ca2+]i induced by bradykinin was totally inhibited by the selective bradykinin B2 receptor antagonist, D-Arg0-Hyp3-Thi5-D-Tic7-Oic8-bradykinin (HOE-140; 10 microM). In contrast, bronchoalveolar lavage cells from ovalbumin-sensitized and -challenged mice significantly responded to both bradykinin and des-Arg9-bradykinin, indicating the presence of both functional bradykinin B1 and B2 receptors. Eosinophils exhibited higher response to des-Arg9-bradykinin (1 microM; 485% increase in [Ca2+]i) compared to bradykinin (1 microM; 163% increase in [Ca2+]i). This des-Arg9-bradykinin-induced [Ca2+]i increase was markedly inhibited by the selective bradykinin B1 receptor antagonist, Ac-Lys-[D-betaNal7, Ile8]des-Arg9-bradykinin (R-715; 10 microM). Des-Arg9-bradykinin neither modified the basal [Ca2+]i in lymphocytes nor in mononuclear cells from ovalbumin-sensitized and challenged mice, while bradykinin produced a [Ca2+]i increase in both cell types. Our results further support the implication of the inducible bradykinin B1 receptors in airway inflammatory response in ovalbumin-sensitized and challenged mice.

Beneficial effect of chronic treatment with the selective bradykinin B1 receptor antagonists, R-715 and R-954, in attenuating streptozotocin-diabetic thermal hyperalgesia in mice

Kinins are important mediators of cardiovascular homeostasis, inflammation and nociception. Bradykinin (BK) B(1) receptors (BKB1-R) are over-expressed in pathological conditions including diabetes, and were reported to play a role in hyperglycemia, renal abnormalities, and altered vascular permeability associated with type 1 diabetes. Recent studies from our laboratory demonstrated that BKB1-R are implicated in streptozotocin (STZ)-diabetes-mediated hyperalgesia, since acute administration of the selective BKB1-R antagonists significantly and dose-dependently inhibited such hyperalgesic activity. In the present study, we examined the effect of chronic treatment of STZ-diabetic mice with the selective BKB1-R agonist desArg9bradykinin (DBK) and two specific antagonists R-715 and R-954, on diabetic hyperalgesia. Diabetes was induced in male CD-1 mice by injecting a single high dose of STZ (200mg/kg, i.p.) and nociception was assessed using the hot plate, plantar stimulation, tail immersion and tail flick tests. Drugs were injected i.p. twice daily for 7 days, starting 4 days after STZ. We showed that chronically administered R-715 (400 micrograms/kg) and R-954 (200 micrograms/kg), significantly attenuated the hyperalgesic effect developed in STZ-diabetic mice as measured by the four thermal nociceptive tests. Further, chronic treatment with DBK (400 micrograms/kg) produced a marked potentiation of the hyperalgesic activity, an effect that was reversed by both R-715 and R-954. The results from this chronic study confirm a pivotal role of the BKB1-R in the development of STZ-diabetic hyperalgesia and suggest a novel approach to the treatment of this short-term diabetic complication using BKB1-R antagonists.