Lingonberry Extract Provides Neuroprotection by Regulating the Purinergic System and Reducing Oxidative Stress in Diabetic Rats.

SCOPE: Beneficial effects produced by polyphenolic compounds are used in the treatment of various diseases, including diabetes. Thus it is relevant to investigate the protective effect of lingonberry extract (LB) on the activities of nucleoside triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase (5'-NT), and adenosine deaminase (ADA); the density of A1, A2A, and P2×7 receptors; production of reactive species (RS); and the levels of thiobarbituric acid reactive substances (TBARS) in the cerebral cortex of streptozotocin-induced diabetic rats. METHODS AND RESULTS: Animals were divided into five groups (n = 10): control/saline; control/LB 50 mg kg-1 ; diabetic/saline; diabetic/LB 25 mg kg-1 ; and diabetic/LB 50 mg kg-1 ; and treated for 30 days. Our results demonstrate that the treatment with LB increased NTPDase activity in the diabetic/LB 50 group compared to diabetic/saline group. Western blot analysis showed that LB restored the density of purinergic receptors to the approximate values of the control/saline group. An increase in the levels of RS and TBARS was observed in the diabetic/saline group compared with the control/saline group, and treatment with LB can prevent this increase. CONCLUSION: This study showed that LB could reverse the modifications found in the diabetic state, suggesting that lingonberry may be a coadjuvant in the treatment of diabetes.

Lion's Mane Medicinal Mushroom, Hericium erinaceus (Agaricomycetes), Modulates Purinoceptor-Coupled Calcium Signaling and Murine Nociceptive Behavior.

Hericium erinaceus is well known for the neurotrophic effect it confers by promoting nerve growth factor biosynthesis. We discovered a novel bioactivity of H. erinaceus in its ability to suppress adenosine triphosphate (ATP)-induced calcium signaling in neuronal PC12 cells. ATP, known primarily as a neurotransmitter, also acts on purinoceptors (P2 purinergic receptor [P2R]) to generate the cellular calcium signaling and secretion that mediate P2R physiological manifestations, including pain. Chronic pain reduces quality of life. However, constant analgesic administration can cause liver and kidney injury, as well as loss of the analgesic effect because of desensitization. In this study we investigated the analgesic potential of H. erinaceus through measurements of ATP-induced Ca2+ signaling in cell lines and observation of pain behaviors in mice. In P2R-coupled Ca2+ signaling measurements, extracts of H. erinaceus mycelia (HEEs) blocked ATP-induced Ca2+ signaling in both rat PC12 cells and human HOS cells. HEEs completely blocked ATP-induced Ca2+ signaling in human HOS cells, suggesting that this effect of HEEs is exerted through the P2R subtypes present in HOS cells, which include the P2X4, P2X7, P2Y2, and P2Y4 subtypes. In observations of animal behavior during pain, HEEs significantly reduced heat-induced pain, including postponing both the tail-flick response to heat stimulation and the paw-lifting response to a hot plate. This study demonstrates novel characteristics of H. erinaceus in reducing nociceptive behavior and blocking the functional activity of P2R. Further studies are required to verify this linkage and its molecular mechanisms.

Curcumin attenuates memory deficits and the impairment of cholinergic and purinergic signaling in rats chronically exposed to cadmium.

This study investigated the protective effect of curcumin on memory loss and on the alteration of acetylcholinesterase and ectonucleotidases activities in rats exposed chronically to cadmium (Cd). Rats received Cd (1 mg/kg) and curcumin (30, 60, or 90 mg/kg) by oral gavage 5 days a week for 3 months. The animals were divided into eight groups: vehicle (saline/oil), saline/curcumin 30 mg/kg, saline/curcumin 60 mg/kg, saline/curcumin 90 mg/kg, Cd/oil, Cd/curcumin 30 mg/kg, Cd/curcumin 60 mg/kg, and Cd/curcumin 90 mg/kg. Curcumin prevented the decrease in the step-down latency induced by Cd. In cerebral cortex synaptosomes, Cd-exposed rats showed an increase in acetylcholinesterase and NTPDase (ATP and ADP as substrates) activities and a decrease in the 5'-nucleotidase activity. Curcumin was not able to prevent the effect of Cd on acetylcholinesterase activity, but it prevented the effects caused by Cd on NTPDase (ATP and ADP as substrate) and 5'-nucleotidase activities. Increased acetylcholinesterase activity was observed in different brain structures, whole blood and lymphocytes of the Cd-treated group. In addition, Cd increased lipid peroxidation in different brain structures. Higher doses of curcumin were more effective in preventing these effects. These findings show that curcumin prevented the Cd-mediated memory impairment, demonstrating that this compound has a neuroprotective role and is capable of modulating acetylcholinesterase, NTPDase, and 5'-nucleotidase activities. Finally, it highlights the possibility of using curcumin as an adjuvant against toxicological conditions involving Cd exposure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 70-83, 2017.

Improvement by phytotherapeutic agent of detrusor overactivity, down-regulation of pharmacological receptors and urinary cytokines in rats with cyclophosphamide induced cystitis.

PURPOSE: We characterized pharmacological effects of the phytotherapeutic agent Eviprostat® on urodynamic parameters, bladder muscarinic and purinergic receptors, and urinary cytokines in rats with cyclophosphamide induced cystitis. MATERIALS AND METHODS: Urodynamic parameters in cyclophosphamide (150 mg/kg intraperitoneally) treated rats were measured by a cystometric method. Muscarinic and purinergic receptors in the bladder and other tissues were measured by radioreceptor assays using [N-methyl-(3)H]scopolamine methyl chloride and [(3)H]αß-MeATP, respectively. The urinary cytokines interleukin-1ß, 6 and 17 were measured with enzyme-linked immunoassay kits. Eviprostat (36 mg/kg per day twice daily for 7 days) was orally administered. RESULTS: On cystometry the micturition interval and micturition volume were significantly decreased in cyclophosphamide vs sham treated rats, while micturition frequency, basal pressure and post-void residual urine volume were significantly increased. Repeat oral administration of Eviprostat in cyclophosphamide treated rats significantly increased the micturition interval and micturition volume, and decreased micturition frequency, basal pressure and post-void residual urine volume. The maximal number of binding sites for [N-methyl-(3)H]scopolamine methyl chloride and [(3)H]αß-MeATP was significantly decreased in the bladder of cyclophosphamide vs sham treated rats. Such decreases were significantly attenuated by repeat Eviprostat treatment. Increased urinary cytokine levels in cyclophosphamide treated rats were also effectively attenuated by Eviprostat. CONCLUSIONS: Repeat Eviprostat treatment significantly improved detrusor overactivity, down-regulated the expression of bladder pharmacological receptors and increased urinary cytokine levels in rats with cyclophosphamide induced cystitis. Therefore, Eviprostat may be a pharmacologically useful phytotherapeutic agent for cystitis.

Adenine induces differentiation of rat hepatic stellate cells.

BACKGROUND AND AIMS: Adenine is a uric acid pathway metabolite of no known function, and has recently been identified as a ligand for a rat G protein-coupled receptor. Due to the known role of other uric acid pathway metabolites in HSC biology, we tested the ability of adenine to induce HSC differentiation. METHODS: RT-PCR was performed for adenine receptor expression in T-6 and primary rat HSC. T-6 and primary rats HSC were cultured with and without adenine, and stellation examined. Next, we examined inhibition of calcium signaling using caged IP(3). To test if adenine inhibits HSC chemotaxis T-6 cells and rat HSCs were cultured with or without adenine for 24 h in a transwell assay with PDGF as the chemoattractant. cDNA was prepared from T-6 and primary HSC for quantification of collagen 1 mRNA using real-time PCR. RESULTS: We found that mRNA for the adenine receptor is expressed in T-6 cells and primary rat HSC. Also, adenine induces HSC stellation and adenine inhibits IP(3) mediated increase in cytosolic [Ca(2+)](i) and inhibits chemotaxis in T-6 cells and primary rat HSC. Adenine was also shown to up-regulate α-SMA and collagen 1, and this effect is lost by using specific si-RNA for the adenine receptor. Finally, adenine inhibits endothelin-1-induced gel contraction. CONCLUSIONS: The adenine receptor is present in T-6 cells and primary rats HSC. Adenine, via the adenine receptor, induces morphological change, and cytosolic calcium signaling, inhibits chemotaxis, and up-regulates collagen 1 mRNA in HSCs.

Muscarinic and alpha 1-adrenergic receptor binding characteristics of saw palmetto extract in rat lower urinary tract.

OBJECTIVES: To elucidate the in vitro and ex vivo effects of saw palmetto extract (SPE) on autonomic receptors in the rat lower urinary tract. METHODS: The in vitro binding affinities for alpha 1-adrenergic, muscarinic, and purinergic receptors in the rat prostate and bladder were measured by radioligand binding assays. Rats received vehicle or SPE (0.6 to 60 mg/kg/day) orally for 4 weeks, and alpha 1-adrenergic and muscarinic receptor binding in tissues of these rats were measured. RESULTS: Saw palmetto extract inhibited specific binding of [3H]prazosin and [N-methyl-3H]scopolamine methyl chloride (NMS) but not alpha, beta-methylene adenosine triphosphate [2,8-(3)H]tetrasodium salt in the rat prostate and bladder. The binding activity of SPE for muscarinic receptors was four times greater than that for alpha 1-adrenergic receptors. Scatchard analysis revealed that SPE significantly reduced the maximal number of binding sites (Bmax) for each radioligand in the prostate and bladder under in vitro condition. Repeated oral administration of SPE to rats brought about significant alteration in Bmax for prostatic [3H]prazosin binding and for bladder [3H]NMS binding. Such alteration by SPE was selective to the receptors in the lower urinary tract. CONCLUSIONS: Saw palmetto extract exerts significant binding activity on autonomic receptors in the lower urinary tract under in vitro and in vivo conditions.

Cholinergic modulation of purinergic and GABAergic co-transmission at in vitro hypothalamic synapses.

The lateral hypothalamus (LH) is an important center for the integration of autonomic and limbic information and is implicated in the modulation of visceral motor and sensory pathways, including those underlying feeding and arousal behaviors. LH neurons in vitro release both ATP and GABA. The control of ATP and GABA co-transmission in LH may underlie the participation of LH in basic aspects of arousal and reinforcement. LH neurons receive cholinergic input from the pedunculopontine and laterodorsal tegmental nuclei as well as from cholinergic interneurons within the LH per se. This study presents evidence for nicotinic acetylcholine receptor (nAChR)-mediated enhancement of GABAergic, but not of purinergic, transmission despite the co-transmission of ATP and GABA at LH synapses in vitro. Facilitation of GABAergic transmission by nicotine is inhibited by antagonists of (alphabeta)*-containing nAChRs, but is unaffected by an alpha7-selective antagonist, consistent with a nAChR-mediated enhancement of GABA release mediated by non-alpha7-containing nAChRs. Activation of muscarinic ACh receptors enhances the release of ATP while concomitantly depressing GABAergic transmission. The independent modulation of ATP/GABAergic transmission may provide a new level of synaptic flexibility in which individual neurons utilize more than one neurotransmitter but retain independent control over their synaptic activity.

Effects of stem bark and leaf extracts of Bridelia ferruginea on rat bladder smooth muscle.

The effects of ethanol extracts of Bridelia ferruginea leaves and stem bark on purinergic neurotransmission in the rat bladder were investigated. The stem bark extract potentiated the contraction of the bladder evoked by exogenous adenosine 5-triphosphate (ATP) but depressed KCl-induced contractions in a dose-related pattern; these two opposite actions might account for the lack of effect on field stimulation of the bladder purinergic nerves. The leaf extract depressed purinergic nerve-mediated contraction of the rat bladder in a dose-related fashion. This action could be attributed to blockade of purinergic neurotransmission since the leaf extract did not affect KCl-induced contractions.

Effects of omega-conotoxin GVIA and diltiazem on double peaked vasoconstrictor responses to periarterial electric nerve stimulation in isolated canine splenic artery.

The actions of omega-conotoxin (omega-CTX) and diltiazem on adrenergic and purinergic components of double peaked vasoconstrictor responses to periarterial nerve stimulation have been investigated in the isolated, perfused canine splenic arterial preparation. Double peaked vasoconstrictions (biphases of vasoconstrictors) were consistently observed in the conditions of 30 s trains of pulses at 1 - 10 Hz frequencies. omega-CTX (1 - 30 nM) produced similar inhibitory effects on the first phase and second phase responses in a dose-related manner. Thirty nM omega-CTX almost completely inhibited the biphasic vasoconstrictions at any used frequencies but did not affect the vasoconstrictor responses to exogenous applied ATP (0.01 - 1 micromol) and noradrenaline (0.03 - 3 nmol). Intraluminal application of a large dose of diltiazem (3 - 10 microM) also produced a dose-dependent inhibitory effect on biphasic vasoconstrictions at any used frequencies. Three microM diltiazem exerted rather a larger inhibitory effect on the second phase than the first phase response at low frequencies (1 - 3 Hz), but a similar inhibition on first and second phasic responses at high frequencies (6 - 10 Hz). An extremely high dose of diltiazem (10 microM) almost completely inhibited the biphasic vasoconstrictor responses to nerve stimulation, and slightly inhibited the contractile responses to exogenous applied ATP (0.01 - 1 micromol) and noradrenaline (0.03 - 3 nmol). The present results indicate that omega-CTX selectively acts prejunctionally to inhibit the release of transmitters from sympathetic nerve terminals, and omega-CTX-sensitive calcium channels may produce a parallel controlling of purinergic and adrenergic components of sympathetic cotransmission. A large dose of diltiazem has inhibitory effects on both prejunctional and postjunctional sympathetic co-transmission. British Journal of Pharmacology (2000) 129, 47 - 52

Effects of Daniellia oliveri bark on isolated rat bladder.

The stem bark of Daniellia oliveri was screened phytochemically and a methanol extract prepared.-Condensed tannins, saponins, cyanogenetic and cardiac glycosides were identified in the crude drug. The cardiac glycoside components in the methanol extract were precipitated with acetone to yield a reddish-brown residue. The n-butanol soluble fraction of an aqueous solution of this residue tested positive for cardiac glycosides and was shown by TLC to contain steroidal compounds. This fraction was subjected to pharmacological studies on isolated rat bladder smooth muscle. It had no effect on purinergic neurotransmission but was a noncompetitive antagonist for muscarinic receptors.

Effects of Daniellia oliveri stem bark and leaf extracts on rat skeletal muscle.

The stem bark and leaves of Daniellia oliveri were screened phytochemically and the effects of their respective methanol extracts on the skeletal muscle of rats were investigated using the isolated phrenic nerve hemidiaphragm muscle preparation. Both were found to contain tannins, cardiac and saponin glycosides. In addition, the bark, but not leaves, contained cyanogenetic glycosides. The methanol extracts were found to possess neuromuscular blocking properties. The leaf extract appeared to act primarily by inhibiting the influx of extracellular Ca(2+) principally by inhibiting K(+) channels. The inhibitory action of the bark extract appeared to be mediated by interference with transmitter release and an action on multiple sites.

Differential control of renal vs. adrenal sympathetic nerve activity by NTS A2a and P2x purinoceptors.

Activation of adenosine A2a and ATP P2x purinoceptors in the subpostremal nucleus tractus solitarii (NTS) via microinjection of the selective agonists CGS-21680 and alpha,beta-methylene ATP (alpha, beta-MeATP), respectively, elicits large dose-dependent decreases in arterial pressure and heart rate, differential regional vasodilation, and differential inhibition of regional sympathetic outputs. With marked hypotensive hemorrhage, preganglionic adrenal sympathetic nerve activity (pre-ASNA) increases, whereas renal (RSNA) and postganglionic adrenal sympathetic nerve activity (post-ASNA) decrease. In this setting, adenosine levels in the brain stem increase. Therefore, we investigated whether stimulation of specific purinoceptors in the NTS may evoke differential sympathetic responses. RSNA was recorded simultaneously with pre-ASNA or post-ASNA in chloralose-urethan-anesthetized male Sprague-Dawley rats. CGS-21680 (2 and 20 pmol in 50 nl) inhibited RSNA and post-ASNA, whereas pre-ASNA increased markedly. alpha,beta-MeATP (25 and 100 pmol in 50 nl) inhibited all sympathetic outputs. Sinoaortic denervation plus vagotomy markedly prolonged the responses to P2x-purinoceptor stimulation. Glutamate (100 pmol in 50 nl) caused differential inhibition of all sympathetic outputs similar to that evoked by alpha,beta-MeATP. We conclude that NTS A2a-purinoceptor activation evokes differential sympathetic responses similar to those observed during hemorrhage, whereas P2x-purinoceptor and glutamate-receptor activation evokes differential inhibition of sympathetic outputs similar to arterial baroreflex responses.

Activation of P2x-purinoceptors in the nucleus tractus solitarius elicits differential inhibition of lumbar and renal sympathetic nerve activity.

Activation of P2x-purinoceptors in the nucleus tractus solitarius (NTS) via microinjection of alpha,beta-methylene ATP (alpha,beta-MeATP) elicits large dose-dependent decreases in mean arterial pressure (MAP) and heart rate (HR) and preferential dilation of the iliac vascular bed in comparison to renal and mesenteric vascular beds. We investigated whether sympathoinhibition contributes to the depressor responses and whether differential changes in regional sympathetic output occur. In 43 chloralose/urethane anesthetized male Sprague-Dawley rats, MAP, HR, renal (RSNA) and lumbar sympathetic nerve activity (LSNA) were recorded. Data were analyzed as both the maximum decrease and the integral of the decrease over the duration of the depressor response. Microinjection of alpha,beta-MeATP (25 and 100 pmol in 50 nl volume) into the subpostremal NTS caused significant and dose-dependent decreases in MAP, HR, RSNA and LSNA. However, the changes in RSNA were significantly greater than those observed in LSNA for both doses and both methods of analysis of data (maximum responses in delta %: 84 +/- 3 vs 62 +/- 4, and 93 +/- 3 vs 74 +/- 4 for low and high dose of alpha,beta-MeATP, respectively; integral responses in delta % x min: 32 +/- 4 vs 18 +/- 3 and 179 +/- 7 vs 134 +/- 14 for low and high dose of alpha,beta-MeATP, respectively). Blockade of P2-purinoceptors in the NTS by the specific P2-receptor antagonist suramin abolished responses to 100 pmol alpha,beta-MeATP and microinjections of vehicle did not alter neural nor hemodynamic parameters. We conclude that activation of P2x-purinoceptors in the NTS inhibits sympathetic nerve activity and evokes differential regional sympathetic responses. However, differential sympathoinhibition does not explain differential vascular responses to the activation of P2x-purinoceptors in the NTS.

Effects of glibenclamide on negative cardiac responses to cholinergic and purinergic stimuli and cromakalim in the isolated dog heart.

We investigated the effects of an ATP-sensitive K+ channel blocker, glibenclamide, on the negative chronotropic and inotropic responses to intracardiac parasympathetic nerve stimulation, acetylcholine (ACh, a muscarinic receptor agonist), ATP (a P2-purinergic receptor agonist), adenosine (a P1-purinergic receptor agonist) and cromakalim (a potassium channel opener) in the isolated, blood-perfused canine right atrium of left ventricle. A high dose of glibenclamide (3 mumol) did not affect the negative chronotropic and inotropic responses to parasympathetic stimulation (frequencies of 1-30 Hz), although it slightly but significantly attenuated the negative cardiac responses to exogenous ACh (0.3-10 nmol). Furthermore, adenosine (0.03-0.3 mumol)-induced negative chronotropic and inotropic responses were significantly inhibited by glibenclamide (3 mumol), but ATP (0.01-1 mumol)-induced negative cardiac responses were not affected. A cumulative administration of cromakalim (0.01-1 mumol) dose-dependently caused much greater decreases in the contractile force of atrial and ventricular muscles than in sinus rate. Glibenclamide (0.3-3 mumol) similarly blocked the negative chronotropic and inotropic responses to cromakalim in a dose-dependent manner. These results suggest that glibenclamide modifies the negative cardiac responses to parasympathetic activation both in pre- and postjunctional sites and the responses to adenosine but not to ATP at K+ channels in the dog heart, although the modifications are minor under physiological conditions.

Expression of a cloned P2Y purinergic receptor that couples to phospholipase C.

P2Y purinergic receptors previously have been shown to couple either to activation of phospholipase C through a pertussis toxin-insensitive mechanism or to inhibition of adenylyl cyclase through pertussis toxin-sensitive members of the G1 family of G proteins. These and other pharmacological data strongly suggest that multiple P2Y purinergic receptors exist. Webb et al. [FEBS Lett. 324:219-225 (1993)] cloned a cDNA that, when expressed in frog oocytes, displayed the general pharmacological characteristics of a P2Y purinergic receptor but whose second messenger linkage was not resolved. We have now cloned the meleagrid (turkey) homologue of the previously cloned chick P2Y purinergic receptor and have stably expressed it in a heterologous human cell line (1321N1 astrocytoma cells) to establish its signaling properties. The purinergic receptor agonist 2-methylthio-ATP (2MeSATP) stimulated a marked activation of phospholipase C in 1321N1 cells stably expressing the meleagrid receptor. The order of potency of a series of analogues of ATP and ADP for stimulation of phospholipase C by the receptor expressed in 1321N1 cells [2MeSATP = 2-methylthio-ADP > adenosine 5'-O-(2-thio)diphosphate > ADP > 2-chloro-ATP = adenosine 5'-O-(3-thio)triphosphate > or = ATP > adenylyl-imidodiphosphate > UTP] was similar to that observed for P2Y purinergic receptors in turkey erythrocytes and many other tissues and was markedly different from those of the P2U and P2X purinergic receptor subtypes. Stimulation of inositol lipid hydrolysis by P2Y purinergic agonists was not affected by preincubation of cells with pertussis toxin. In contrast to its marked effects on phospholipase C activity, 2MeSATP caused only a small and variable inhibition of cAMP accumulation. Ribonuclease protection analysis of turkey tissues showed that this P2Y purinergic receptor is most highly expressed in blood and brain. Taken together, these results indicate that a phospholipase-C-activating P2Y purinergic receptor has been cloned and stably expressed in 1321N1 astrocytoma cells.

Stimulation of phospholipase C in cultured microvascular endothelial cells from human frontal lobe by histamine, endothelin and purinoceptor agonists.

1. Cultures of endothelial cells derived from the microvasculature of human frontal lobe have been investigated for phospholipase C (PLC) responses to histamine, endothelins and purinoceptor agonists. 2. Using cells prelabelled with [3H]-inositol and measuring total [3H]-inositol (poly)phosphates, histamine acting at H1 receptors stimulated a substantial response with an EC50 of about 10 microM. 3. Endothelin-1 also gave a clear stimulation of phosphoinositide-specific phospholipase C. Both concentration-response curves and binding curves showed effective responses and binding in the rank order of endothelin-1 > sarafotoxin S6b > endothelin-3, suggesting an ETA receptor. 4. Assay of total [3H]-inositol (poly)phosphates showed no response to the purinoceptor agonists, 2-methylthioadenosine 5'-trisphosphate (2MeSATP), adenosine 5'-O-(3-thiotrisphosphate) (ATP gamma S) or beta,gamma-methylene ATP. Both ATP and UTP gave a small PLC response. 5. Similarly, when formation of [32P]-phosphatidic acid from cells prelabelled with 32Pi was used as an index of both PLC and phospholipase D, a small response to ATP and UTP was seen but there was no response to the other purinoceptor agonists tested. 6. Study by mass assay of stimulation by ATP of inositol (1,4,5) trisphosphate accumulation revealed a transient response in the first few seconds, a decline to basal, followed by a small sustained response. 7. These results show that human brain endothelial cells in culture are responsive to histamine and endothelins in a manner which may regulate brain capillary permeability. Purines exert a lesser influence.

Adenosine in the heart: its emerging roles.

An important regulator of cardiac rhythm and coronary blood flow, adenosine is finding valuable applications in treatment and diagnosis. It should soon be available for cardiac imaging and eventually as a protective agent against acute myocardial infarction and reperfusion injury. Study of adenosine's uses is providing insights into its biologic effects in a variety of organ systems.

Effects of oblongine chloride, an alkaloid from Leontice leontopetalum on guinea-pig isolated smooth muscle and heart.

1. The effects of (-)oblongine chloride, a quaternary alkaloid from Leontice leontopetalum, on guinea-pig isolated ileal longitudinal segments, main pulmonary artery rings, spontaneously-beating atrium and isolated perfused heart were studied. 2. Oblongine chloride (3 x 10(-5)-10(-3) M) caused concentration-dependent relaxation of ileum, an effect which was not blocked by propranolol (10(-6) M) alone or in combination with prazosin (3 x 10(-8) M), or by indomethacin (10(-6) M), but was reduced by desensitization of the preparation by prior exposure to 3 x 10(-5) M ATP and, at high concentrations of oblongine, by a combination of propranolol and yohimbine (3 x 10(-6) M). 3. Oblongine chloride (10(-5)-3 x 10(-3) M) caused concentration-dependent relaxation of epinephrine-precontracted pulmonary artery. This effect was not affected by propranolol or by indomethacin but was significantly attenuated by pretreatment with 3 x 10(-5) M ATP and potentiated by pretreatment with quinacrine (10(-5) M). 4. Oblongine chloride (10(-5) M-3 x 10(-3) M) caused concentration-dependent increase in the contractility but did not affect the rate of the atrium. Similar effects were obtained with isolated perfused heart except that large concentrations of oblongine (10(-3), 3 x 10(-3) M) inhibited both contractility and rate of the heart. The inotropic effects of oblongine on the atrium were not blocked by propranolol or indomethacin but were significantly blocked by quinacrine.(ABSTRACT TRUNCATED AT 250 WORDS)

Frog secretions and hunting magic in the upper Amazon: identification of a peptide that interacts with an adenosine receptor.

A frog used for "hunting magic" by several groups of Panoan-speaking Indians in the borderline between Brazil and Peru is identified as Phyllomedusa bicolor. This frog's skin secretion, which the Indians introduce into the body through fresh burns, is rich in peptides. These include vasoactive peptides, opioid peptides, and a peptide that we have named adenoregulin, with the sequence GLWSKIKEVGKEAAKAAAKAAGKAALGAVSEAV as determined from mass spectrometry and Edman degradation. The natural peptide may contain a D amino acid residue, since it is not identical in chromatographic properties to the synthetic peptide. Adenoregulin enhances binding of agonists to A1 adenosine receptors; it is accompanied in the skin secretion by peptides that inhibit binding. The vasoactive peptide sauvagine, the opioid peptides, and adenoregulin and related peptides affect behavior in mice and presumably contribute to the behavioral sequelae observed in humans.