Adherence in diabetes: can we define it and can we measure it?

The effects of a beta 3-adrenoceptor agonist on insulin-induced changes in lipid metabolism were studied in obese male Zucker (fa/fa) rats during euglycaemic clamp. Rats were treated with BRL 35135 (R*, R*-(+/-)-methyl-4-[2-[2-hydroxy-2-(3-chlorophenyl)-ethyl-amino]-propyl] phenoxyacetate hydrobromide) (0.5 mg/kg per day in drinking water) for three weeks before an euglycaemic hyperinsulinaemic clamp was performed. Insulin infusion lowered serum non-esterified fatty acids and plasma glycerol more efficiently in BRL 35135-treated than in control rats although plasma insulin remained significantly lower in the BRL 35135-treated than in the control rats during the clamp. In conclusion, chronic treatment with BRL 35135 potentiates the effect of insulin on lipid metabolism.     

In vitro inhibition of human colonic motility with SR 59119A and SR 59104A: evidence of a beta3-adrenoceptor-mediated effect

The new beta3-adrenoceptor is present in the gastrointestinal tract of various species. This study aimed to show that this receptor modulates human colonic motility in vitro. We used circular muscle strips from the human colon suspended in single organ baths containing Krebs solution and subjected to an initial 1.5-2 g tension. We measured the effects of different beta3-adrenoceptor agonists, including SR 59104A (N-[(6-hydroxy-1,2,3,4-tetrahydronaphthalen-(2R)-2-yl)methyl]-(2 R)-2-hydroxy-2-(3-chlorophenyl)ethanamine hydrochloride), SR 59119A (N-[(7-methoxy-1,2,3,4-tetrahydronaphthalen-(2R)-2-yl)methyl]-(2R) -2-hydroxy-2-(3-chlorophenyl)ethanamine hydrochloride), BRL 37344 (R,R + S,S) [4-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino] propyl] phenoxy] acetic acid), and of isoprenaline and salbutamol in the absence or in the presence of propranolol alone or in combination with the beta3-adrenoceptor antagonist SR 59230A (3-(2-ethylphenoxy)-1-[(1S)-1,2,3,4-tetrahydro-naphthalen-1- ylamino]-(2S)-2-propanol oxalate) on amplitude of spontaneous contractions. To evaluate a possible beta2-adrenoceptor-mediated effect, we studied the action of these compounds on human isolated bronchi. On the human isolated colon, SR 59119A, SR 59104A and isoprenaline reduced the initial amplitude of spontaneous contractions by 60%. The curves obtained in the presence of antagonists suggested an action mediated by beta3-adrenoceptor stimulation, since propranolol did not antagonize the action of SR 59119A and SR 59104A, whereas the combination of propranolol and SR 59230A significantly displaced the concentration-response curve of these agonists to the right. This study provides pharmacological evidence of modulation of human colonic motility, and especially of the amplitude of spontaneous contractions, by the atypical beta-adrenoceptor, the beta3-adrenoceptor.     

Beta-3 adrenoceptor-mediated increase in cutaneous blood flow in the dog

Beta-3 adrenergic agonist administration decreases arterial blood pressure in the dog as previously shown. The putative presence of beta-3 adrenoceptors in peripheral microvascular muscle was studied in dogs through measurement of cutaneous blood flow and skin temperature changes. Experiments were carried out in normal and sinoaortic denervated dogs (i.e., animals deprived of baroreceptor pathways). In normal dogs, the infusion of 0.4 nmol/kg/min of 4-[-[(2-hydroxy-(3-chlorophenyl)ethyl)-amino]propyl] phenoxyacetate (BRL 37344) or (R,R-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]-1,3- benzodioxole-2,2-dicarboxylate (CL 316243) (two selective beta-3 adrenoceptor agonists), or 8 nmol/kg/min of 4-[3-t-butylamino-2-hydroxypropoxy]benzimidazol-2-one (CGP 12177) (a beta-1/beta-2 adrenergic antagonist also reported to act as an agonist for the beta-3 adrenoceptor) induced an increase in heart rate and cutaneous blood flow (evaluated in the internal part of the ear) and a decrease in blood pressure. The skin and the buccal mucous membrane became purplish. The infusion of (-)-isoproterenol (0.4 nmol/g/min), a dose known to stimulate preferentially beta-1/beta-2 adrenoceptors, or sodium nitroprusside (12 micrograms/kg/min) increased heart rate and decreased blood pressure, but reduced cutaneous blood flow. In sinoaortic denervated dogs, similar effects on cutaneous blood flow and blood pressure were observed. However, in these animals, heart rate remained unchanged whatever the infused drug. BRL 37344 (but not isoproterenol) increased cutaneous temperature in normal dogs. This study suggests that beta-3 adrenoceptors exist in canine cutaneous vascular smooth muscles and that their stimulation induces vasodilatation.     

Studies towards the synthesis of the hypermodified nucleoside of rat liver phenylalanine transfer ribonucleic acid: improved synthesis of the base beta-hydroxywybutine

An improved synthesis of the key intermediates (3 and 8) for the synthesis of beta-hydroxywybutines [[R-(R*,S*)]- and [S-(R*,R*)]-4], the most probable structures for the minor base from rat liver tRNA(Phe), has been achieved by the Wittig reaction between 1-benzyl-7-formylwye (1) and the phosphorane derived from (R)-2-[(methoxycarbonyl)amino]-3-(triphenylphosphonio)propanoate (10), followed by methylation, OsO4 oxidation, and cyclocondensation with COCl2 in the presence of pyridine. The racemic forms of beta-hydroxywybutines [(R*,S*)- and (R*,R*)-4], which were required for the determination of the optical purity of [R-(R*,S*)]- and [S-(R*,R*)]-4 by means of chiral HPLC, were conveniently prepared through pyrolysis of the cyclic carbonate 3 followed by NaBH4 reduction and catalytic hydrogenolysis. The samples of [R-(R*,S*)]- and [S-(R*,R*)]-4 were thus shown to be optically pure.     

Role of cardiomyopathy in Noonan''s syndrome. Apropos of a case]

Dehydrocorydaline, an active principle of Corydalis bulbosa alkaloids, in concentrations of 10(-5) M to 5 x 10(-5)M inhibited relaxation and the concomitant release of (3H)-noradrenaline caused by 10(-4)M nicotine and electrical perivascular nerve stimulation in the taenia caecum of guinea pig. The same inhibitory effects were observed on contraction and release of (3H) noradrenaline in the sympathetic nerve-pulmonary artery preparation of rabbit. On the other hand, neither relaxation nor contraction caused by exogenously applied noradrenaline was affected. These results suggest that the inhibitory action of dehydrocorydaline on the relaxation or contraction, produced by nicotine and electrical nerve stimulation, is due to blockade of noradrenaline release from the adrenergic nerve terminals in both the taenia caecum and pulmonary artery. Participation of the adrenergic neuron blocking action of dehydrocorydaline in preventing experimental ulceration is discussed.     

Desensitization of beta3-adrenergic receptor-stimulated adenylyl cyclase activity and lipolysis in rats

The beta3-adrenergic receptor is an integral membrane protein consisting of seven transmembrane domains. Unlike the beta1 and beta2 receptors, this subtype lacks the consensus phosphorylation sites required for desensitization by serine kinases. Using the rodent specific beta3 agonist BRL 35135, our initial data indicated that beta3 receptor-mediated glycerol levels progressively decreased following daily oral doses of 5 mg/kg. Therefore, we initiated studies designed to delineate the possible mechanism(s) for this decreased response. Within 3 hours following a single oral dose of BRL 35135, serum glycerol levels and UCP (uncoupling protein) RNA levels were significantly increased whereas beta3 RNA levels were significantly decreased. Rats were dosed daily for 5 days with either vehicle or BRL 35135 (5 mg/kg, p.o.) and blood samples were collected for glycerol analysis. Adipose tissue was excised for lipolysis and adenyl cyclase measurements. In addition, UCP and beta3 receptor RNA levels were assessed. No effect on adipocyte BRL 37344-stimulated adenylyl cyclase activity was observed 3 hours following the initial dose of BRL 35135. Although a slight decrease (approximately 25%) in adenylyl cyclase activity could be observed 24 hours following the initial dose, it wasn't until day 4 of dosing that a significant decrease (50%) was observed. In contrast, beta3- stimulated lipolysis in adipocytes from BRL 35135-treated rats was decreased 85% within 24 hours and this decrease persisted through four days of treatment. These data indicate that the lipolytic response to beta3 receptor activation is decreased after only a single oral dose of BRL 35135, whereas receptor-mediated adenylyl cyclase activation, although initially unaffected, also desensitizes by day four of treatment.     

Regulation of the DBP promoter by PAR proteins and in leukemic cells bearing an E2A/HLF translocation

YM158 (3-[(4-tert-butylthiazol-2-yl)methoxy]-5'-[3-(4-chlorobenzenesu lfonyl ) propyl]-2'-(1H-tetrazol-5-ylmethoxy)benzanilide monosodium salt monohydrate) antagonizes leukotriene (LT) D4 and thromboxane (TX) A2 receptors. Functional assays in vitro showed that YM158 exhibits competitive dual antagonism of LTD4 and TXA2 receptor-mediated contraction of isolated guinea pig tracheae, with pA2 values of about 8.87 and 8.81, respectively. Its antagonistic activity for the LTD4 receptor was approximately 6.5 times less potent than that of montelukast, and that for the TXA2 receptor was 2.5 times more potent than that of seratrodast. YM158 also inhibited PGD2- and PGF2alpha-induced tracheal contractions. YM158 showed no antagonism against LTC4-, histamine- or carbachol-induced contractions of guinea pig tracheae. Furthermore, YM158 antagonized the stable TXA2 analog U46619-induced aggregation of both guinea pig and human platelets and inhibited the LTD4-induced contraction of guinea pig ileum. From these results, YM158 appears to be a novel, selective dual antagonist for both LTD4 and TXA2 receptors.     

A search for new 5-HT1A/5-HT2A receptor ligands. In vitro and in vivo studies of 1-[omega-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-ones

A series of 1-?omega-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-one derivatives 2-14 was synthesized in order to obtain ligands with a dual 5-HT1A/5-HT2A activity. The majority of those compounds (2-5, 7, 10-13) exhibited a high 5-HT1A (Ki = 2-44 nM) and/or 5-HT2A affinity (Ki = 51 and 39 for 5 and 7, respectively). Induction of lower lip retraction (LLR) and behavioral syndrome and inhibition of these effects evoked by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) were used for determination the agonistic and antagonistic activity, respectively, at 5-HT1A receptors. The 5-HT2A antagonistic activity was assessed by the blocking effect on the head twitches induced by (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in mice. Two of the tested compounds, 1-?3-[4-(3-chlorophenyl)-1-piperazinyl]propyl?-6-fluoroindolin-2(1 H)-one (5) and 1-?3-[4-(2-methoxyphenyl)-1-piperazinyl]propyl?indolin-2(1H)-one (7), demonstrated a high 5-HT1A/5-HT2A affinity and an in vivo antagonistic activity towards both receptor subtypes.     

Pharmacological characteristics of MJ-451, a new benzopyran- derived ATP-sensitive potassium channel opener, in guinea pig isolated trachea

In this study, we determined the pharmacological activities of MJ-451 (6-cyano-3S,4R-dihydro-2, 2-dimethyl-2H-3-hydroxy-4-[2-oxo-5S-1-hydroxmethyl)-1-pyrrolidinyl ]-1 -benzopyran) in guinea pig isolated trachea and compared its effects with those of cromakalim. MJ-451 (0.1-10 micromol/l) and cromakalim (0.01-1 micromol/l) produced concentration-dependent relaxation of guinea pig isolated trachea precontracted with carbachol (0.5 micromol/l) or histamine (1 micromol/l). MJ-451 (0.03-30 micromol/l), as well as cromakalim (0.03-30 micromol/l), caused a complete and concentration-dependent relaxation of guinea pig isolated trachea precontracted with 20 mmol/l KCl, but did not inhibit the spasmogenic effect of 80 mmol/l KCl. However, theophylline (30-3,000 micromol/l) caused a complete and concentration-dependent relaxation of guinea pig isolated trachea precontracted with either 20 or 80 mmol/l KCl. Propranolol (0.1 micromol/l) markedly antagonized the relaxant action of isoprenaline, but not that of MJ-451 in carbachol-contracted isolated trachea. 8-(p)-sulfophenyltheophylline (150 micromol/l), a selective P1 purinoceptor antagonist, had no effect against the tracheal relaxation induced by MJ-451, but markedly depressed the concentration-response curve of 5'-N-ethylcarboxamidoadenosine. Charybdotoxin (10 micromol/l), a large-conductance Ca2+-activated K+ channel blocker, failed to modify the relaxant activity of MJ-451 in carbachol-contracted isolated trachea. The ATP-sensitive K+ channel blocker, glibenclamide (0.1, 1 and 10 micromol/l) concentration-dependently antagonized the relaxant activity of MJ-451 in carbachol-contracted isolated trachea. It is concluded that MJ-451 is a selective ATP-sensitive K+ channel opener in the tracheal smooth muscle of the guinea pig.     

Effects of ONO-1101, a novel beta-antagonist, on action potential and membrane currents in cardiac muscle

Direct effects of ONO-1101 ?(-)-[(S)-2,2-dimethyl-1,3-dioxolan-4-yl]methyl-3-[4-[(S) -2-hydroxy-3-(2-morpholino carbonylamino)ethylamino] propoxy]phenylpropionate monohydrochloride), a novel beta-antagonist, on action potential parameters and membrane currents, and its beta adrenoceptor antagonism were examined in cardiac muscle. Action potential-parameters in papillary muscle of reserpinized animals and membrane currents recorded from single myocytes obtained from guinea pig and rabbit hearts were not affected by 1 to 100 microM ONO-1101. On the other hand, ONO-1101 markedly inhibited the potentiation of Ca current by isoproterenol in single cardiac myocytes of the guinea pig. The concentration-response relationship of Ca current for isoproterenol was shifted to the right. This effect resembled that of esmolol, which is also a beta adrenoceptor antagonist. A Schild plot analysis revealed the slope and pA2 value of each antagonist (ONO-1101, 0.94, 8.0; and esmolol, 0.98, 7.3, respectively) and demonstrated that ONO-1101 is about 5 times more potent than esmolol as a beta-antagonist. Two other effects of isoproterenol: 1) potentiation of delayed rectifier K current and 2) activation of chloride current, were also inhibited by ONO-1101. The time required for 50% removal of beta-antagonism of ONO-1101 and esmolol after the washout was estimated as 4 and 6 min, respectively, in depolarized papillary muscle. These results suggest that ONO-1101 is a potent beta-antagonist whose effects were removed quickly by washout. When applied at what is thought to be a clinical dosage, ONO-1101 had no direct effects on action potential-parameters and membrane currents in cardiac muscle. These characteristics of ONO-1101 suggest that this agent may be effective in clinical use.     

Acute effects of the beta 3-adrenoceptor agonist, BRL 35135, on tissue glucose utilisation

1. The acute effects of BRL 35135 (BRL) on tissue glucose utilisation index (GUI) in vivo were investigated in anaesthetized rats by use of 2-deoxy-[3H]-glucose. 2. Intravenous injection of BRL caused a dose-dependent increase in GUI in skeletal muscle, and white and brown adipose tissue; plasma insulin and fatty acid concentrations were also increased. Chronic treatment with BRL added to the diet caused a 34 fold increase in basal GUI of brown adipose tissue (BAT), but had no effect on GUI in other tissues. After chronic treatment, the acute tissue response to an intravenous maximal dose of BRL had disappeared completely in all tissues apart from the soleus muscle. 3. A high dose (20 mg kg-1) of the non-selective beta-antagonist, propranolol, inhibited the acute effect of BRL on GUI in BAT, but failed to affect GUI in muscle. A lower dose (1 mg kg-1) of the antagonist also inhibited the BAT response, but had little or no effect on the response in Type I (working) muscles such as soleus and adductor longus (ADL), and potentiated the response in Type II (non-working) muscles such as tibialis and extensor digitorium longus (EDL). 4. A low dose (1 mg kg-1) of the selective beta 1-antagonist, atenolol, had no effect on the BRL response but the same dose of the selective beta 2-antagonist, ICI 118551, potentiated significantly the effect of BRL on GUI in most muscles without altering plasma insulin levels. 5. It is concluded that: (i) the heterogeneous tissue responses of different muscle fibre types in the presence of P-antagonists indicates that BRL affects muscle GUI directly, in addition to effects mediated by increases in plasma insulin concentration; (ii) the resistance of the BRL response to conventional P-adrenoceptor antagonists implicates an atypical adrenoceptor mediating the GUI response in skeletal muscle, but this may not be identical to the adipose tissue P3-adrenoceptor; (iii) the potentiation of BRL responses by ICI 118551 indicates an inhibitory P2-adrenoceptor-mediated component in the muscle GUI response to BRL.     

The interaction of McN-A-343 with muscarine receptors in cardiac and smooth muscle

The interaction of the muscarine receptor partial agonist (4-m-chlorophenylcarbamoyloxy)-2-butynyltrimethylammonium chloride (McN-A-343) was investigated at muscarine receptors in the atria and taenia caeci of the guinea-pig to compare its interaction at the muscarine M2 receptor in the two tissues. In the smooth muscle, the muscarine M3 receptor subtype is responsible for the contractile response but the major subtype detected in binding or antibody experiments is the M2 subtype. In guinea pig atria the dissociation constant of McN-A-343 at muscarine receptors was 15.2 microM determined in functional experiments on left atria in McEwen's solution or 14.8 microM in binding experiments with [3H]-(-)-quinuclidinyl benzilate ([3H]QNB) in the same medium containing 5'-guanylylimododiphosphate (50 microM). In the taenia caeci, the dissociation constant estimated for McN-A-343 at the M3 receptor from functional experiments based on the contractile response to the agonist in McEwen's solution was 4.6 microM. This value was similar to the dissociation constant (6.2 microM) estimated from binding studies versus [3H]QNB conducted in the same medium although studies with 11-[[2-[(diethylamino)methyl]-1-piperidinyl]acetyl]-5,11-dihydro-6H- pyrido[2,3-b][1,4]benzodiazepine 6-one (AF-DX 116) versus [3H]-(-)-N-methylscopolamine suggested that 70% of the receptors were the M2 subtype. The presence of the M2 subtype in the taenia caeci was also confirmed by the ability of oxotremorine to inhibit the increase in cAMP produced by isoprenaline (10 microM) since apparent pKB values for AF-DX 116 and hexahydrosiladiphenidol were 6.95 and 6.75, respectively. McN-A-343 (100 microM) failed to inhibit the response to isoprenaline and did not antagonize the inhibitory response to oxotremorine. It is concluded that the apparent affinity of McN-A-343 for muscarine M2 receptors in the atria and the taenia caeci differs and a number of explanations are discussed.     

Antinociceptive profile of 3-alpha-tropanyl 2-(4-Cl-phenoxy)butyrate (SM-21) [corrected]: a novel analgesic with a presynaptic cholinergic mechanism of action

The antinociceptive effect of (+/-)-3-alpha-tropanyl 2-(4-Cl-phenoxy)butyrate [corrected] (SM-21) (10-40 mg kg(-1) s.c., 10-30 mg kg(-1) i.p., 20-60 mg kg(-1) p.o., 3-20 mg kg(-1) i.v. and 5-20 microg per mouse i.c.v.) was examined in rodents and guinea pigs by using the hot-plate, abdominal constriction, tail-flick and paw-pressure tests. The antinociception produced by (+/-)-SM-21 was prevented by atropine, pirenzepine and hemicholinium-3 but not by quinpirole, R-(alpha)-methylhistamine, [1-[2(methylsufonyl)amino]ethyl]-4-piperidinyl]methyl-5-floro++ +-2-methoxy-1H-indole-3-carboxylate hydrochloride, N6-cyclopentyladenosine, 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine hydrobromide, naloxone, 3-aminopropyl-diethoxy-methyl-phosphinic acid or reserpine. On the basis of the above data, it can be postulated that (+/-)-SM-21 exerted an antinociceptive effect mediated by a central potentiation of cholinergic transmission. Affinity profiles of (+/-)-SM-21 for muscarinic receptor subtypes, determined by functional studies (rabbit vas deferens for M1, guinea pig atrium for M2, guinea pig ileum for M3 and immature guinea pig uterus for putative M4) have shown a selectivity ratio M2/M1 of 4.6 that, although very low, might be responsible for the antinociception induced by (+/-)-SM-21 through an increase in ACh extracellular levels. In the antinociceptive dose range, (+/-)-SM-21 did not impair mouse performance evaluated by the rota-rod and hole-board tests.     

1 beta-Methyl-2-(5-substituted pyrrolidin-3-ylthio)carbapenems. 3. Synthesis and antibacterial activity of BO-2727 and its related compounds

The synthesis and biological activity of (1R,5S,6S)-2-[(3S,5S)- 5-substituted pyrrolidin-3-ylthio]- 6-[(R)-1-hydroxyethyl]-1-methyl-1-carbapen-2-em-3-carboxylic acid in which hydroxy-substituted aminoethyl, aminopropyl, and aminobutyl groups were introduced as substituents, are described. These derivatives showed potent antibacterial activity against Gram-positive and Gram-negative bacteria including P. aeruginosa. Among them, lenapenem (BO-2727, 7b), carrying an (R)-1-hydroxy-3-(N-methylamino)propyl group, was selected as a development candidate.     

Nonparticipation of adrenergic mechanism in potassium-induced relaxation of taenia from guinea pig caecum

In the isolated taenia caeci of guinea pigs excess potassium (10-30 mM) induced a phasic relaxation followed by a contraction. This phasic relaxation was unaffected by treatment with hexamethonium, phentolamine, propranolol and bretylium. However, relaxation induced by perivascular nerve stimulation was inhibited by all these agents but not by hexamethonium. Tetrodotoxin inhibited both forms of relaxation. Potassium-induced relaxation was not accompanied by [3H]noradrenaline release. Perivascular nerve stimulation caused release of [3H]noradrenaline and this was blocked by bretylium. Treatment with ouabain or replacement of NaCl by LiCl, but not treatment by cold storage, inhibited the potassium-induced relaxation. These results suggest that the potassium-induced relaxation of taenia caeci was due to electrogenic sodium pumping and was independent of the adrenergic innervation of the tissue.     

Analysis of the mechanisms underlying the biphasic responses to bradykinin in circular muscle from guinea pig ileum

Experiments were designed to further characterize the receptor mediating the biphasic response to bradykinin in circular muscle from guinea pig ileum in vitro by the use of HOE 140, a potent and specific bradykinin antagonist. D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]bradykinin (HOE 140, 0.1-1000 nM) caused a graded inhibition of bradykinin (10 nM)-induced contraction and relaxation responses in circular muscle from guinea pig ileum, with IC50s of 4 and 10 nM respectively. However, the potency of HOE 140 to antagonize the bradykinin (300 nM)-induced contraction and relaxation was decreased about 6-fold (IC50 22 nM) and 57-fold (IC50 570 nM). HOE 140 (3-100 nM) caused parallel and concentration-dependent rightward displacements of bradykinin (0.1-3000 nM)-induced biphasic concentration-response curves in circular muscle from guinea pig ileum. Schild regression plots yielded straight lines with slopes not significantly different from unity and pKb values of 9.0 and 8.7 against bradykinin-induced contraction and relaxation, respectively. Similar pKb values (8.7) were obtained for HOE 140 against bradykinin-mediated contraction in the longitudinal muscle of the guinea pig ileum. The action of HOE 140 was selective for bradykinin, since response to other agonists were not affected. It is concluded that HOE 140 does not discriminate the receptors mediating the biphasic responses to bradykinin in circular muscle from guinea pig ileum, as it showed a similar selective, competitive and reversible antagonism against both components of the bradykinin response in this preparation.     

Direct contractile effect of cholecystokinin octapeptide on caecal circular smooth muscle cells of guinea pig via both CCK-A and CCK-B/gastrin receptors

This study was designed to investigate the participation of cholecystokinin(CCK)-A and/or CCK-B/gastrin receptors in CCK-8-induced contraction of guinea pig caecal circular smooth muscle cells, using a novel selective CCK-A receptor antagonist, (S)-N-[1-(2-fluorophenyl)-3,4,6,7-tetrahydro-4-oxo-pyrrolo-[3,2,1-jk] [1,4]benzodiazepine-3-yl]-1H-indole-2-carboxamide (FK480), and a novel selective CCK-B/gastrin receptor antagonist, (R)-1-[2,3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl-1H-1, 4-benzodiazepine-3-yl]-3-(3-methylphenyl)urea (YM022). Concentration-response curves for the contractile effect of CCK-8 alone and in the presence of 0.1nM FK480, 0.1 nM YM022, or a combination of 0.1 nM FK480 and 0.1 nM YM022 on isolated smooth muscle cells were determined. In addition, the inhibitory effects of various concentrations of FK480 or YM022 on 1 nM CCK-8-induced contraction were examined. At a concentration of 0.1 nM, both FK480 and YM022 shifted the concentration-response curve for CCK-8 to the right (about 100 times) with the same potency. In addition, a concentration-response curve for a combination of 0.1 nM FK480 and 0.1 nM YM022 was shifted to the right (about 100 times) of the curves for 0.1 nM FK480 alone or 0.1 nM YM022 alone. Both antagonists inhibited 1 nM CCK-8-induced contraction of caecal circular smooth muscle cells in a concentration-dependent manner, with the similar inhibitory potency. A significant inhibition was obtained at a concentration as low as 0.1 nM FK480 and 0.1 nM YM022. This study strongly suggested the presence of both CCK-A and CCK-B/gastrin receptors in caecal circular smooth muscle cells of guinea pig, and that the contractile effect of CCK-8 on these cells was mediated via both of these receptors.     

Atypical beta-adrenoceptors in the rat isolated common carotid artery

1. The possible existence of atypical beta-adrenoceptors in vascular smooth muscle of the rat common carotid artery was examined in this study. 2. Isoprenaline produced concentration-dependent relaxation of noradrenaline (10(-7) M) precontracted ring segments of the carotid artery. The relaxation was not affected by endothelial denudation. 3. Propranolol (10(-8) M-3 x 10(-7) M) shifted the isoprenaline curve to the right without suppressing the maximum response. However, the slope (0.74) of the Schild plot was significantly (P < 0.05) less than 1. 4. Salbutamol (beta 2), CGP 12177 and BRL 37344 (beta 3) also concentration-dependently relaxed noradrenaline precontracted artery segments. These relaxations were not affected by propranolol (10(-7) M). Pretreatment of the artery segments with BRL 37344 did not desensitize the tissue to the relaxant effect of isoprenaline, CGP 12177 and salbutamol. 5. It is concluded that atypical beta-adrenoceptors exist in vascular smooth muscle of the common carotid artery.     

Pyrazolopyridine derivatives act as competitive antagonists of brain adenosine A1 receptors: [35S]GTPgammaS binding studies

The effects of adenosine receptor ligands and three novel pyrazolopyridine derivatives on guanosine-5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) binding to rat cerebral cortical membranes were examined. [35S]GTPgammaS binding was stimulated in a concentration dependent manner by several adenosine receptor agonists. The adenosine A2a receptor selective agonist, 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680), was ineffective confirming specificity for adenosine A1 receptor activation. 2-Chloro-N6-cyclopentyladenosine (CCPA; 10(-7) M)-stimulated [35S]GTPgammaS binding was inhibited by xanthine and pyrazolopyridine based adenosine receptor antagonists. The concentration-response curve for CCPA-stimulated [35S]GTPgammaS binding was shifted to the right with increasing concentrations of antagonist without significant changes in maximal response. Schild analyses determined pK(B) values of 8.97, 8.88, 8.21, 8.16, 7.79 and 7.65 for 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), (R)-1-[(E)-3-(2-phenylpyrazolo[1,5a]pyridin-3-yl) acryloyl]-2-piperidine ethanol (FK453), 6-oxo-3-(2-phenylpyrazolo[1,5a]pyridin-3-yl)-1(6H)-pyridazinebutyric+ ++ acid (FK838), 9-chloro-2-(2-furyl)[1,2,4]triazolo-[1,5c]quinazolin-5-amine (CGS 15943), 8-cyclopentyl-1,3-methylxanthine (CPT) and (R)-1-[(E)-3-(2-phenylpyrazolo[1,5a]pyridin-3-yl) acryloyl]-piperidin-2-yl acetic acid (FK352), respectively. Schild slopes were close to unity, confirming that these novel pyrazolopyridine derivatives act as competitive antagonists at rat brain adenosine A1 receptors.