Antiemetic effects of morphine on motion- and drug-induced emesis in Suncus murinus

Emetic and antiemetic effects of morphine were investigated in Suncus murinus. Subcutaneous (up to 30 mg/kg) or intracerebroventricular administration (50 micrograms) of morphine failed to cause emesis. However, pretreatment with morphine (s.c.) prevented the emesis induced by nicotine (10 mg/kg, i.p.), copper sulfate (40 mg/kg, p.o.), cisplatin (20 mg/kg, i.p.) and motion stimulus. These results suggest that morphine has only antiemetic potency and may block a common mechanism for the emetic reflex of suncus, because the antiemetic effects of the drug were exerted irrespective of the stimulus.     

Characterization of adenosine receptors evoking excitation of mesenteric afferents in the rat

We examined the effects of adenosine receptor agonists and antagonists on the discharge of mesenteric afferent nerves supplying the jejunum in pentobarbitone sodium-anaesthetized rats. Adenosine (0.03-10 mg kg(-1), i.v.), NECA (0.3-300 microg kg(-1), i.v.) and the A1 receptor agonist, GR79236 (0.3-1000 microg kg(-1), i.v.), each induced dose-dependent increases in afferent nerve activity and intrajejunal pressure, hypotension and bradycardia. The A1 receptor antagonist, DPCPX (3 mg kg(-1), i.v.), antagonized all the effects of GR79236 but only the haemodynamic effects of adenosine and NECA. The A2A receptor antagonist, ZM241385 (3 mg kg(-1), i.v.), antagonized the hypotensive effect of NECA but none of the effects of GR79236. The A2A receptor agonist, CGS21680 (0.3-300 microg kg(-1), i.v.), and the A3 receptor agonist, IB-MECA (0.3-300 microg kg(-1), i.v.), each induced only a dose-dependent hypotension. Subsequent administration of adenosine (3 mg kg(-1), i.v.) induced increases in afferent nerve activity and intrajejunal pressure and bradycardia. ZM241385 (3 mg kg(-1), i.v.) antagonized the hypotensive effect of CGS21680 but not the effects of adenosine. Bethanechol (300 microg kg(-1), i.v.) evoked increases in afferent nerve activity and intrajejunal pressure, hypotension and bradycardia. However, adenosine (3 mg kg(-1), i.v.) evoked greater increases in afferent nerve activity than bethanechol despite inducing smaller increases in intrajejunal pressure. In summary, A1 and A2B and/or A2B-like receptors evoke adenosine-induced increases in mesenteric afferent nerve activity and intrajejunal pressure in the anaesthetized rat. Furthermore, elevations in intrajejunal pressure do not wholly account for adenosine-evoked excitation of mesenteric afferent nerves.     

Assessment of the role of alpha2-adrenoceptor subtypes in the antinociceptive, sedative and hypothermic action of dexmedetomidine in transgenic mice

1. The role of alpha2-adrenoceptor (AR) subtypes in the modulation of acute nociception, motor behaviour and body temperature, has been investigated by determining the activity of the alpha2AR selective agonist dexmedetomidine (Dex) in mice devoid of individual alpha2AR subtypes through either a point (alpha2A) or null (alpha2B/alpha2C) mutation ('knock-out'). 2. In a rodent model of acute thermal nociception, the mouse tail immersion test, Dex, in wild type (WT) control animals, produced a dose-dependent increase in the threshold for tail withdrawal from a 52 degrees C water bath with mean ED50 values of 99.9+/-14.5 (alpha2A), 94.6+/-17.8 (alpha2B) and 116.0/-17.1 (alpha2C) microg kg(-1), i.p. 3. In comparison to the WT controls, Dex (100-1000 microg kg(-1), i.p.), was completely ineffective as an antinociceptive agent in the tail immersion test in the alpha2A AR D79N mutant animals. Conversely, in the alpha2B AR and alpha2C AR knock-outs, Dex produced a dose-dependent antinociceptive effect that was not significantly different from that observed in WT controls, with ED50 values of 85.9+/-15.0 (P>0.05 vs WT control) and 226.0+/-62.7 (P>0.05 vs WT control) microg kg(-1) i.p., respectively. 4. Dex (10-300 microg kg(-1), i.p.) produced a dose-dependent reduction in spontaneous locomotor activity in the alpha2A, alpha2B and alpha2C AR WT control animals with ED50 values of 30.1+/-9.0, 23.5+/-7.1 and 32.3+/-4.6 microg kg(-1), i.p., respectively. Again, Dex (100-1000 microg kg(-1), i.p.) was ineffective at modulating motor behaviour in the alpha2A AR D79N mutants. In the alpha2B AR and alpha2C AR knock-out mice, Dex produced a dose-dependent reduction in spontaneous locomotor activity with ED50 values of 29.1+/-6.4 (P>0.05 vs WT control) and 57.5+/-11.3 (P>0.05 vs WT control) microg kg(-1), respectively. 5. Dex was also found to produce a dose-dependent reduction in body temperature in the alpha2A, alpha2B and alpha2C AR WT control mice with ED50 values of 60.6+/-11.0, 16.2+/-2.5 and 47.2+/-9.1 microg kg(-1), i.p., respectively. In the alpha2A AR D79N mutants, Dex had no effect on body temperature at a dose (100 microg kg(-1), i.p.) that produced a significant reduction (-6.2+/-0.5 degrees C; P<0.01 vs vehicle) in temperature in WT controls. However, higher doses of Dex (300 and 1000 microg kg(-1), i.p) produced a small, but statistically significant decrease in temperature corresponding to -1.7+/-0.4 degrees C and -2.4+/-0.3 degrees C (both P<0.01 vs vehicle), respectively. In the alpha2B AR and alpha2C AR knock-out mice, Dex produced a dose-dependent reduction in body temperature with ED50 values of 28.4+/-4.8 (P>0.05 vs WT control) and 54.1+/-8.0 (P>0.05 vs WT control) microg kg(-1), respectively. 6. In conclusion, the data are consistent with the alpha2A AR being the predominant subtype involved in the mediation of the antinociceptive, sedative and hypothermic actions of Dex. This profile would appear to indicate that an alpha2A AR subtype selective analgesic will have a narrow therapeutic window, particularly following systemic administration.     

Rapid method for obtaining high-quality chromosome banding in the study of hematopoietic neoplasia

The antiemetic effects of six serotonergic 5-HT1A-receptor agonists, 8-hydroxy-2-(di-n-propylamino)tetrarin (8-OH-DPAT), 4-(4-[4-(2-pyrimidinyl)piperazin-1-yl]butyl)-2,3,4,5- tetrahydro-1,4-benzoxazepine-3,5-dione (SUN8399), buspirone, gepirone, ipsapirone and tandospirone, against motion sickness were investigated in Suncus murinus. Subcutaneous injection of all six agonists completely and dose-dependently suppressed motion-induced emesis. Pretreatment with 8-OH-DPAT or SUN8399 dose-dependently inhibited emesis elicited by nicotine (4.0 mg/kg, s.c.), veratrine (0.7 mg/kg, s.c.), cisplatin (20 mg/kg, i.p.) and copper sulfate (40 mg/kg, p.o.). These results suggest that serotonergic 5-HT1A-receptor agonists are effective as anti-motion sickness drugs, and these drugs may block a common mechanism(s) for the emetic reflex of the suncus because the antiemetic effects of the 5-HT1A-receptor agonists were exerted irrespective of the stimulus.     

Tissue response to covered Wallstents

8-epi prostaglandin F2alpha(8-epi PGF2alpha) contracted rat thoracic aorta rings in a concentration-dependent manner in the presence or absence of functional endothelium [median effective concentration (EC50) values, 455+/-52 and 268+/-34 nM, respectively; Student's t test; p=0.006]. U46619 was a more potent agonist with or without functional endothelium (EC50 values, 6.8+/-1.6 and 4.5+/-1.0 nM, respectively). SQ29548 [a thromboxane (TP)-receptor antagonist] inhibited contractions to both 8-epi PGF2alpha and U46619 in a competitive manner, with mean pA2 values of 8.3 and 7.9, respectively. 8-Epi PGF2alpha had a further contractile effect in vessels that had been contracted with noradrenaline and had been shown to possess a functional endothelium. Inhibition of thromboxane synthesis with OKY-046 or blockade of endothelin receptors with bosentan had no effect on responses to 8-epi PGF2alpha or U46619. Preincubation with 8-epi PGF2alpha or noradrenaline shifted the concentration-response curves to U46619 upward at low concentrations of U46619 with no significant change in EC50 values or maximal responses. Reduction of TP-receptor number in rat aorta with dithiothreitol caused a concentration-dependent inhibition of responses to both U46619 and 8-epi PGF2alpha, with no effect on maximal responses and or on the responses to U46619 after the preincubation with 8-epi PGF2alpha. These results indicate that 8-epi PGF2alpha is a potent vasoconstrictor in the rat aorta and are suggestive of an action of 8-epi PGF2alpha at the TP receptor.     

Antidepressant-like effects of endogenous histamine and of two histamine H1 receptor agonists in the mouse forced swim test

1. Effects of substances which are able to alter brain histamine levels and two histamine H1 receptor agonists were investigated in mice by means of an animal model of depression, the forced swim test. 2. Imipramine (10 and 30 mg kg(-1), i.p.) and amitriptyline (5 and 15 mg kg(-1), i.p.) were used as positive controls. Their effects were not affected by pretreatment with the histamine H3 receptor agonist, (R)-alpha-methylhistamine, at a dose (10 mg kg(-1), i.p.) which did not modify the cumulative time of immobility. 3. The histamine H3 receptor antagonist, thioperamide (2-20 mg kg(-1), s.c.), showed an antidepressant-like effect, with a maximum at the dose of 5 mg kg(-1), which was completely prevented by (R)-alpha-methylhistamine. 4. The histamine-N-methyltransferase inhibitor, metoprine (2-20 mg kg(-1), s.c.), was effective with an ED50 of 4.02 (2.71-5.96) mg kg(-1); its effect was prevented by (R)-alpha-methylhistamine. 5. The histamine precursor, L-histidine (100-1000 mg kg(-1), i.p.), dose-dependently decreased the time of immobility [ED30 587 (499-712) mg kg(-1)]. The effect of 500 mg kg(-1) L-histidine was completely prevented by the selective histidine decarboxylase inhibitor, (S)-alpha-fluoromethylhistidine (50 mg kg(-1), i.p.), administered 15 h before. 6. The highly selective histamine H1 receptor agonist, 2-(3-trifluoromethylphenyl)histamine (0.3-6.5 microg per mouse, i.c.v.), and the better known H1 agonist, 2-thiazolylethylamine (0.1-1 microg per mouse, i.c.v.), were both dose-dependently effective in decreasing the time of immobility [ED50 3.6 (1.53-8.48) and 1.34 (0.084-21.5) microg per mouse, respectively]. 7. None of the substances tested affected mouse performance in the rota rod test at the doses used in the forced swim test. 8. It was concluded that endogenous histamine reduces the time of immobility in this test, suggesting an antidepressant-like effect, via activation of H1 receptors.     

Increases in retinovascular prostaglandin receptor functions by cyclooxygenase-1 and -2 inhibition

PURPOSE: To determine the relative contribution of cyclooxygenase (COX)-1 and COX-2 in regulating prostaglandin (PG) E2 and PGF2alpha receptors (EP and FP, respectively) densities and their functions in retinal vasculature of neonatal pigs. METHODS: Newborn pigs were treated intravenously every 8 hours for 48 hours with saline, 40 mg/kg nonselective COX inhibitor ibuprofen, 80 mg/kg COX-1 inhibitor valeryl salicylate, or 5 mg/kg DuP697 and 5 mg/kg NS398, COX-2 inhibitors. Retinal microvessel EP and FP receptor densities were measured by radioligand binding and receptor-coupled effects by determining second-messenger inositol 1,4,5-trisphosphate (IP3) and vasomotor responses. Retinal blood flow (RBF) response to incremental increases in blood pressure (BP) was measured by a microsphere technique. RESULTS: Valeryl salicylate, DuP697, and NS398 reduced retinal PGE2 and PGF2alpha concentrations in the newborn by approximately half, whereas ibuprofen caused further reduction to levels observed in adults. Retinal vessel EP1, EP3, and FP receptor densities increased approximately threefold after treatments with COX-1 or COX-2 inhibitors, and five- to sixfold after ibuprofen treatment. EP and FP receptor upregulation was associated with corresponding increases in IP3 production and retinal vasoconstriction in response to PGF2alpha, fenprostalene (an FP agonist), PGE2, 17-phenyl trinor PGE2 (an EP1 agonist), and M&B28,767 (an EP3 agonist) and with enhanced RBF autoregulation of high BP (> or =125 mm Hg). Conversely, EP2 receptor density and coupled functions were minimally affected by COX inhibition. CONCLUSIONS: Data suggest that increased COX-1- and COX-2-catalyzed prostaglandin synthesis contribute equivalently to the downregulation of retinovascular EP1, EP3, and FP receptors and their vasoconstrictor functions in newborn pigs; the EP2 receptor was not significantly influenced by ontogenic alterations in prostaglandin levels.     

Effects of gavage versus dosed feed administration on the toxicokinetics of benzyl acetate in rats and mice

8-epi-prostaglandin F2 alpha stimulated contraction of human myometrial strips obtained from five different donors at the time of hysterectomy with a pEC50 value of 6.3 +/- 0.5. In paired strips from the same donors the pEC50 value for the selective TP receptor agonist U46619 ([1R-[1a,4a,5b(Z),6a(1E,3S*)]]-7-[6-(3- hydroxy-1-octenyl)-2-oxabicyclo[2.2.1]hept-5-yl]-5-heptenoic acid) was 8.3 +/- 0.4. In strips from four other donors 8-epi-prostaglandin F2 alpha was ineffective whereas the pEC50 for U46619 was 6.9 +/- 0.3. Responses to 8-epi-prostaglandin F2 alpha were unaffected by the selective DP receptor antagonist BW A868C (3-benzyl-5-(6-carboxyhexyl)-1-(2- cyclohexyl-2-hydroxyethylamino)hydantoin) at 50 nM but were blocked by the selective TP receptor antagonist L670596 ((-)6,8-difluoro-9-p-methylsulfonyl benzyl-1,2,3,4- tetrahydrocarbazol-1-yl-acetic acid) at 50 nM. The pIC50 values obtained when the TP receptor antagonists GR 32191 ([1R- [1 alpha(Z),2 beta,3 beta,5 alpha]]-(+)-7-[5-[[(1,1'-biphenyl)-4- yl]methoxy]-3-hydroxy-2-(1-piperidinyl)cyclopentyl]-4-heptenoic acid), ICI D1542 ((4(Z)-6-[(2S,4S,5R)-2-[1-methyl-1-(2-nitro-4-tolyloxy)ethyl]- 4-(3-pyridyl)-1,3-dioxan-5-yl]hex-4-enoic acid), ICI 192605 (4(Z)-6-[(2,4,5-cis)-2-(2-chlorophenyl)-4-(2-hydroxyphenyl)-1,3- dioxan-5-yl]hexenoic acid), L670596 and SQ 29548 ([1S-(1 alpha,2 beta(5Z),3 beta,4 alpha]]-7- [3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7- oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid) were added cumulatively to strips pre-contracted with an EC80 concentration of 8-epi-prostaglandin F2 alpha were not significantly different from those obtained when an EC80 concentration of U46619 was used. The effects of 8-epi-prostaglandin F2 alpha on strips pre-contracted with an EC80 concentration of U46619 were not different from those of U46619 itself. It is concluded that in the non-pregnant human myometrium 8-epi-prostaglandin F2 alpha is a medium potency contractile agonist acting predominantly at the TP receptor.     

Effects of talipexole on motor behavior in normal and MPTP-treated common marmosets

Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 0.5 mg/animal i.v. once or twice) to common marmosets induced persistent parkinsonian motor deficits. The postsynaptic dopamine D2 receptor agonist properties of talipexole (B-HT 920, 2-amino-6-allyl-5,6,7,8-tetrahydro-4H-thiazolo[4,5-d]-azepine), which is believed to be a dopamine autoreceptor agonist, were examined using normal and MPTP-treated marmosets and were compared to these properties of bromocriptine, a selective dopamine D2 receptor agonist. Talipexole (20-160 micrograms/kg i.p.) dose dependently increased motor activity and reversed the akinesia and incoordination of movement in MPTP-treated marmosets. In normal marmosets, higher doses of talipexole (80-160 micrograms/kg i.p.) produced a dose-dependent increase in motor activity, while the lowest dose (20 micrograms/kg i.p.) depressed this activity. These data for talipexole were very similar to those for bromocriptine. Talipexole had, however, several properties different from those of bromocriptine; it had a rapid onset of antiparkinsonian activity compared to bromocriptine; it had more than 25 times as much activity potency as bromocriptine; a dose of talipexole (80 micrograms/kg i.p.) sufficient to produce the activity did not induce emesis as strongly as an insufficient dose of bromocriptine (0.5 mg/kg i.p.). These results suggest that talipexole has postsynaptic dopamine D2 receptor agonist properties and that these properties of talipexole may be favorable in the treatment of Parkinson's disease.     

Role of rpoS in the regulation of glutathione oxidoreductase (gor) in Escherichia coli

Caffeine (10-40 mg/kg, p.o.) enhanced locomotor activity (LA). Administration of GABA antagonist, bicuculline (0.5-1.0 mg/kg, i.p.), potentiated this caffeine-induced increase of LA, as well as LA of control rats. Treatment with the GABA agonist, muscimol (0.25-1 mg/kg, i.p.) or dopaminergic antagonist, haloperidol (0.25-1 mg/kg, i.p.) or muscarinic receptor blocker, atropine (3.75-5 mg/kg, i.p.), or inhibitor of acetylcholine esterase physostigmine (0.05-0.30 mg/kg, i.p.) or nicotine (0.5-1.5 mg/kg, i.p.) an nicotinic receptor agonist all decreased the LA of both caffeine-treated and control rats. Haloperidol-induced reduction in caffeine-induced increase in LA was found to be withdrawn with higher dose of caffeine. The dopamine agonist L-Dopa (75-150 mg/kg, p.o.) along with carbidopa (10 mg/kg, p.o.) increased the LA in control rats and potentiated the LA of caffeine treated rats. The haloperidol attenuated the bicuculline-induced increase in LA and atropine or physostigmine attenuated the bicuculline or L-Dopa + carbidopa-induced increase in LA in both caffeine treated and control rats when those drugs were administered concomitantly with bicuculline or L-Dopa+carbidopa. These results suggest that (a) the GABAergic system has direct role in the regulation of LA, and (b) caffeine potentiates LA by antagonism of the adenosine receptor and activation of the dopaminergic system which, in turn, reduces GABAergic activity through the reduction of cholinergic system.     

Effects of a peer-led senior health education program

Serotonin (5-hydroxytryptamine; 5-HT) elicits external carotid vasoconstriction in vagosympathectomized dogs via 5-HT1B/1D receptors and a mechanism unrelated to the 5-HT1, 5-HT2, 5-HT3 and 5-HT4 types. In order to further explore the nature of this novel mechanism, the canine external carotid effects of 2-(2-aminoethyl)-quinoline (D-1997), a novel 5-HT1 receptor agonist, were analyzed and compared with those of 5-HT and sumatriptan. Intracarotid (i.c.) infusions of 5-HT, D-1997 and sumatriptan to vagosympathectomized dogs dose-dependently decreased external carotid conductance, the rank order of agonist potency being 5-HT > sumatriptan > D-1997. The effects to D-1997 were resistant to intravenous (i.v.) pretreatment with 5-HT2 and 5-HT3/5-HT4 receptor antagonists. Remarkably, the effects induced by lower (10-100 microg/min), but not higher (300-1000 microg/min), doses of D-1997 were blocked by high doses of methiothepin (1 and 3 mg/kg, i.v.), as previously shown with 5-HT. In addition, GR-127935 (1-10 microg/kg, i.v.), partially and dose-dependently antagonized D-1997-induced responses. However, the effects of D-1997 remained unaltered after blockade of alpha- and beta-adrenoceptors, muscarinic, nicotinic, histamine and dopamine receptors, or inhibition of 5-HT-uptake or cyclo-oxygenase, depletion of biogenic amines or blockade of Ca2+ channels. These results may support our previous contention that lower doses of 5-HT elicit external carotid vasoconstriction in vagosympathectomized dogs by activation of 5-HT1B/1D receptors, whilst higher doses of 5-HT stimulate a novel vasoconstrictor mechanism.     

Supplemental dietary arginine accelerates intestinal mucosal regeneration and enhances bacterial clearance following radiation enteritis in rats

Medetomidine was administered to sheep and horses at a dose rate of 5 microg kg(-1) (i.v.). Heart rate and blood pressure were recorded. Medetomidine induced bradycardia and a biphasic blood pressure response consisting of a transient hypertension followed by hypotension. Administration of prazosin (an alpha1 adrenoceptor antagonist; 100 microg kg(-1), i.v.) had no effect on the cardiovascular response to medetomidine (5 microg kg(-1), i.v.), but inhibited the cardiovascular response of methoxamine (an alpha1 adrenoceptor agonist; 75 microg kg(-1), i.v.). L-659,066 (an alpha2 adrenoceptor antagonist which does not cross the blood brain barrier; 264 microg kg(-1), i.v.) attenuated the medetomidine induced bradycardia, but had no effect on the cardiovascular response to methoxamine. L659,066 also reduced the medetomidine induced hypertension in sheep, but had less effect on the horse. It is concluded that both alpha1 and alpha2 adrenoceptors are important in the control of cardiovascular function in horses and sheep. Medetomidine appears to act on alpha2 adrenoceptors alone in the sheep. The cardiovascular effects of medetomidine in the horse are complex and may be influenced by central alpha2 adrenoceptor regulation or effects on other receptor subtypes as well as direct stimulation of peripheral alpha2 adrenoceptors.     

The effect of central angiotensin II receptor blockade on interleukin-1beta- and prostaglandin E-induced fevers in rats: possible involvement of brain angiotensin II receptor in fever induction

We investigated the role of the brain angiotensin II (Ang II) receptor subtypes AT1 and AT2 in the development of fever induced in freely moving rats by administration of interleukin-1beta (IL-1beta) or prostaglandin E2 (PGE2). Intraperitoneal (i.p.) injection of IL-1beta (2 microg/kg) induced a marked fever of rapid onset. Intracerebroventricular (i.c.v.) administration, immediately before IL-1beta injection, of a selective AT2 receptor antagonist, CGP42112A (5 or 20 microg), reduced the fever in a dose-related manner. Rats given an i.c.v. injection of PGE2 (200 ng) developed a monophasic fever response that was attenuated by i.c.v. treatment with CGP42112A (10 or 20 microg) in a dose-related manner. The IL-1beta (2 microg/kg i.p.)- and PGE2 (200 ng i.c.v.)-induced fevers were unchanged by the selective AT1 receptor antagonist losartan (60 microg i.c.v.). Treatment with exogenous Ang II (100 ng i.c.v.), which itself had no effect on resting body temperature, resulted in an enhancement of the PGE2 (50 ng i.c.v.)-induced fever. The administration of CGP42112A (2 and 5 microg) into the rostral hypothalamus (preoptic/anterior hypothalamic region) reduced fevers induced by IL-1beta (2 microg/kg i.p.) or intrahypothalamic (i.h.) PGE2 (100 ng). Moreover, i.h. injection of Ang II (25 ng) augmented the PGE2 (25 ng i.h.)-induced fever. Finally, the i.h. administration, 15 min before i.h. PGE2 (100 ng), of the angiotensin-converting enzyme (ACE) inhibitor lisinopril (5 and 10 microg) attenuated the PGE2-induced fever. These results suggest that brain AT2 receptors contribute to the induction of such febrile responses in rats.     

Intracellular Ca2+ elevation and contraction due to prostaglandin F2alpha in rat aorta

Prostaglandin F2alpha was tested to determine (a) whether its effect on intracellular Ca2+ levels ([Ca2+]i) and force in vascular smooth muscle was mediated through activation of the thromboxane A2 and/or prostaglandin receptor, and (b) the relative roles of Ca2+ influx via L-type and non-L-type Ca2+ channels in prostaglandin receptor-mediated contraction. [Ca2+]i and force were measured simultaneously in fura-2-loaded rat aortic strips. The thromboxane A2 receptor antagonist, SQ29548 ([1S]-1a,2b(5Z),3b,4a-7-(3-[2-[(phenylamino)carbonyl] hydrazinomethyl)-7-oxobicyclo-[2.2.1]hept-2-yl-5-heptenoic acid), prevented the prostaglandin F2alpha-induced plateau [Ca2+]i elevation and force by 80-90%, while abolishing these responses due to the thromboxane A2 receptor agonist, U46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy prostaglandin F2alpha). Prostaglandin F2alpha (+ SQ29548)-induced plateau [Ca2+]i elevation and force were not inhibited by verapamil. Ni2+, a non-selective cation channel blocker, in the presence of verapamil, abolished the prostaglandin F2alpha (+ SQ29548)-elevated [Ca2+]i, while the contraction was only partially inhibited. These results suggest that, in rat aorta, (1) elevated [Ca2+]i and force due to high prostaglandin F2alpha concentrations largely results from thromboxane A2 receptor activation, and (2) the prostaglandin component of the prostaglandin F2alpha-induced contraction is dependent on Ca2+ influx via non-L-type channels.     

Exogenous and endogenous catecholamines inhibit the production of macrophage inflammatory protein (MIP) 1 alpha via a beta adrenoceptor mediated mechanism

Noradrenaline (NA) and adrenaline (Ad) are modulators of cytokine production. Here we investigated the role of these neurotransmitters in the regulation of macrophage inflammatory protein (MIP)-1alpha expression. Pretreatment of RAW 264.7 macrophages with NA or Ad decreased, in a concentration-dependent manner (1 nM-100 microM), MIP-1alpha release induced by bacterial lipopolysaccharide (LPS 10 ng ml(-1) LPS). The effect of NA was reversed by the selective beta-adrenoceptor antagonist propranolol (10 microM), but not by the alpha-adrenoceptor antagonist phentolamine (10 microM). In the concentration range of 10 nM-10 microM, isoproterenol, a beta-adrenoceptor agonist, but not phenylephrine (a selective alpha1-adrenoceptor agonist) or UK-14304 (a selective alpha2-adrenoceptor agonist) mimicked the inhibitory effects of catecholamines on MIP-1alpha production. Increases in intracellular cyclic adenosine monophosphate, elicited either by the selective type IV phosphodiesterase inhibitor rolipram (0.1 - 10 microM), or by prostaglandin E2, (10 nM-10 microM) decreased MIP-1alpha release, suggesting that increased cyclic AMP may contribute to the suppression of MIP-1alpha release by beta-adrenoceptor stimulation. Northern blot analysis demonstrated that NA (100 nM-10 microM), Ad, isoproterenol, as well as rolipram (100 nM-10 microM) decreased LPS-induced MIP-1alpha mRNA accumulation. NA and Ad (1-100 microM) also decreased MIP-1alpha production in thioglycollate-elicited murine peritoneal macrophages. Pretreatment of mice with either isoproterenol (10 mg kg(-1), i.p.) or rolipram (25 mg kg(-1), i.p.) decreased LPS-induced plasma levels of MIP-1alpha, while propranolol (10 mg kg(-1), i.p.) augmented the production of this chemokine, confirming the role of a beta-adrenoceptor mediated endogenous catecholamine action in the regulation of MIP-1alpha production in vivo. Thus, based on our data we conclude that catecholamines are important endogenous regulators of MIP-1alpha expression in inflammation.     

In vivo functional interaction between phencyclidine binding sites and sigma receptors to produce head-weaving behavior in rats

To investigate the in vivo functional interaction between phencyclidine (1-(1-phenylcyclohexyl)piperidine; PCP) binding sites and sigma receptors, we examined the effects of sigma receptor ligands on stereotyped head-weaving behavior induced by PCP, a putative PCP/sigma receptor ligand, and (+)-5-methyl-10,11-dihydroxy-5H-dibenzo(a,d)cyclo-hepten-5,10-imin e ((+)-MK-801; dizocilpine), a selective PCP binding site ligand, in rats. PCP (7.5 mg/kg, i.p.)-induced head-weaving behavior was inhibited by both N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)-phenyl]-ethylamine (NE-100; 0.03-1.0 mg/kg, p.o.), a selective sigma1 receptor ligand, and alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperidine butanol (BMY-14802; 3 and 10 mg/kg, p.o.), a prototype sigma receptor ligand, in a dose-dependent manner, whereas NE-100 (0.1-1.0 mg/kg, p.o.) and BMY-14802 (3 and 10 mg/kg, p.o.) did not inhibit dizocilpine (0.25 mg/kg, s.c.)-induced head-weaving behavior. These results suggest that NE-100 and BMY-14802 act via sigma receptors. Dizocilpine-induced head-weaving behavior was potentiated by 1,3-di-o-tolyl-guanidine (DTG; 0.03-0.3 microg/kg, i.v.) and (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine ((+)-3-PPP; 3 and 6 mg/kg, i.p.), sigma1/sigma2 receptor ligands, as well as by (+)-N-allyl-normetazocine ((+)-SKF-10,047: 8 mg/kg, i.p.), a sigma1 receptor ligand, while DTG (0.3 microg/kg, i.v.), (+)-3-PPP (6 mg/kg, i.p.) and (+)-SKF-10,047 (8 mg/kg, i.p.) did not induce this behavior. Potentiation of dizocilpine-induced head-weaving behavior by DTG (0.3 microg/kg, i.v.), (+)-3-PPP (6 mg/kg, i.p.) and (+)-SKF-10,047 (8 mg/kg, i.p.) was completely blocked by NE-100 (0.1 mg/kg, p.o.) and BMY-14802 (10 mg/kg, p.o.). These results suggest that PCP binding sites and sigma receptors are involved in PCP-induced head weaving behavior, and that sigma1 receptors play an important role in modulation of the head-weaving behavior.     

AGN 191976: a novel thromboxane A2-mimetic with ocular hypotensive properties

The possible subdivision of thromboxane A2-sensitive (TP) receptors is currently a controversial subject. We report herein on a novel thromboxane A2 mimetic, AGN 191976, which has almost identical pharmacological activity to the well-characterized prostaglandin H2/thromboxane A2 (PGH2/TxA2) mimetic U-46619, but its effects on intraocular pressure are quite distinct from U-46619. Prostanoid receptor activity was determined in vitro using different smooth muscle assays and platelets. Intraocular pressure was measured tonometrically in ocular normotensive Beagle dogs and Cynomolgus monkeys. Conjunctival microvascular permeability was determined in guinea pigs. Despite closely resembling U-46619 as a potent and selective TP receptor agonist, AGN 191976 was a potent ocular hypotensive in dogs and monkeys whereas U-46619 did not lower IOP in either species. The ocular hypotensive effect of AGN 191976 in dogs was attenuated by pretreatment with the TP receptor antagonist SQ 29548. Thus, the ocular hypotensive effects of AGN 191976 are consistent with TP receptor stimulation. Both TxA2-mimetics caused plasma leakage in the guinea pig conjunctiva. The disparate activities of U-46619 and AGN 191976 in our studies suggest the existence of heterogeneous populations of TP-receptors in the eye.     

Characterization of the recombinant human prostanoid DP receptor and identification of L-644,698, a novel selective DP agonist

1. A human embryonic kidney cell line [HEK 293(EBNA)] stably expressing the human recombinant prostaglandin D2 (PGD2) receptor (hDP) has been characterized with respect to radioligand binding and signal transduction properties by use of prostanoids and prostanoid analogues. Radioligand binding studies included saturation analyses, the effects of nucleotide analogues, the initial rate of ligand-receptor association and equilibrium competition assays. In addition, adenosine 3':5'-cyclic monophosphate (cyclic AMP) generation in response to ligand challenge was also measured, as this is the predominant hDP signalling pathway. 2. L-644,698 ((4-(3-(3-(3-hydroxyoctyl)-4-oxo-2-thiazolidinyl) propyl) benzoic acid) (racemate)) was identified as a novel ligand having high affinity for hDP with an inhibitor constant (Ki) of 0.9 nM. This Ki value was comparable to the Ki values obtained in this study for ligands that have previously shown high affinity for DP: PGD2 (0.6 nM), ZK 110841 (0.3 nM), BW245C (0.4 nM), and BW A868C (2.3 nM). 3. L-644,698 was found to be a full agonist with an EC50 value of 0.5 nM in generating cyclic AMP following activation of hDP. L-644,698 is, therefore, comparable to those agonists with known efficacy at the DP receptor (EC50): PGD2 (0.5 nM), ZK 110841 (0.2 nM) and BW245C (0.3 nM). 4. L-644,698 displayed a high degree of selectivity for hDP when compared to the family of cloned human prostanoid receptors: EP1 (> 25,400 fold), EP2 (approximately 300 fold), EP3-III (approximately 4100 fold), EP4 (approximately 10000 fold), FP (> 25,400 fold), IP (> 25,400 fold) and TP (> 25,400 fold). L-644,698 is, therefore, one of the most selective DP agonists as yet described. 5. PGJ2 and delta12-PGJ2, two endogenous metabolites of PGD2, were also tested in this system and shown to be effective agonists with Ki and EC50 values in the nanomolar range for both compounds. In particular, PGJ2 was equipotent to known DP specific agonists with a Ki value of 0.9 nM and an EC50 value of 1.2 nM.     

Caspase 1-independent IL-1beta release and inflammation induced by the apoptosis inducer Fas ligand

Anchietia salutaris tea is traditionally used in Brazil to treat allergies, suggesting it contains compounds with antagonistic activity on the allergic mediators. We have evaluated extracts and semi-purified fractions of Anchietia salutaris as a source of compounds having this type of antagonism on the contraction induced in guinea-pig lung parenchymal strips and on platelet aggregation and shape change. After 10 min pre-incubation dichloromethane extracts containing 30 or 100 microg mL(-1) inhibited the contraction induced by prostaglandin D2 (PGD2) in guinea-pig lung parenchymal strips with dose ratios (DR) of 0.76+/-0.14 and 0.93+/-0.19, respectively; the amount of inhibition depended both on the concentration and on the time of pre-incubation (DR after 30 min pre-incubation was 1.21+/-0.51). The dichloromethane extract and its semi-purified fractions also inhibited the contractions induced by U46619, a more potent, stable, synthetic agonist of thromboxane A2 (TxA2) prostanoid (TP) receptors, the receptors acted upon by PGD2 to produce lung contractions. The dichloromethane extract did not inhibit the lung parenchymal contractions induced by histamine, leukotriene D4 (LTD4) or platelet-activating factor (PAF). Platelet aggregation induced by U46619, adenosine 5'-diphosphate (ADP) or PAF was not inhibited by the dichloromethane extract. Indeed, the extract potentiated platelet aggregation induced by low concentrations of these agonists and also potentiated the shape change induced by U46619. These results imply that the dichloromethane extract of Anchietia salutaris and its semi-purified fractions contain an active principle that competitively inhibits TxA2 TP receptors, the stimulation of which causes lung parenchymal contraction. The inhibition seems to be selective for this receptor subtype, because the extract fails to inhibit platelet aggregation or shape change. This provides additional support of earlier reports suggesting the occurrence of TP receptor subtypes.     

Anorectic activity of prostaglandin precursors

1 Intraperitoneal and intragastric (i.g.) administration of prostaglandin precursors arachidonic (2 mg, 15 mg/kg, i.p; 30 mg/kg i.g.), linolenic (100 mg/kg i.p.; 200 mg/kg, i.g.) and linoleic (15, 100 mg/kg, i.p.; 100 mg/kg, i.g.) acids to 22 h food-deprived rats inhibits food intake. 2 This anorexia is similar to that induced by prostaglandin F2alpha (1 mg/kg, i.p.). 3 At anorectic doses these fatty acids do not cause pyrexia, in fact arachidonic acid causes hypothermia. 4 Prior treatment with indomethacin (15 mg/kg) and paracetamol (50 mg/kg) specifically reverses the anorexia and the behavioural satiety induced by the three fatty acids, while not affecting prostaglandin F2alpha-induced suppression of food intake. 5 Results of the present experiments suggest that both physiological and pharmacological modification of appetite could be brought about through an effect on prostaglandin generating systems.