Central antidopaminergic properties of 2-bromolisuride, an analogue of the ergot dopamine agonist lisuride

2-Bromolisuride (2-Br-LIS), a derivative of the ergot dopamine (DA) agonist lisuride, was investigated in rodents in comparison with the DA antagonist haloperidol with regard to its influence on DA related behaviour, cerebral DA metabolism and prolactin (PRL) secretion. 2-Br-LIS produced catalepsy in mice (ED50 3.3 mg/kg i.p.), antagonized apomorphine-induced stereotypies in mice (ED50 0.4 mg/kg i.p.), antagonized DA agonist-induced stereotypies in rats (0.1-1.56 mg/kg i.p.), inhibited locomotor activity in rats (0.025-6.25 mg/kg i.p.), antagonized the hyperactivity produced by various DA agonists in rats (0.025-6.25 mg/kg i.p.) and inhibited the apomorphine-induced hypothermia in mice (0.05-0.78 mg/kg i.p.). 2-Br-LIS (0.03-10 mg/kg i.p.) stimulated DA biosynthesis and DOPAC formation in the striatum and DA rich limbic system of rats, but had no effect on serotonin turnover. In striatum and limbic forebrain of gamma-butyrolactone-pretreated rats 2-Br-LIS reversed the apomorphine-induced inhibition of DOPA accumulation. 2-Br-LIS (0.03 - 3 mg/kg) enhanced PRL secretion in intact male rats. These findings indicate DA antagonistic properties of 2-Br-LIS presumably due to blockade of central pre- and postsynaptic DA receptors being of approximately the same order of potency as haloperidol. 2-Br-LIS is the first ergot compound with definite antidopaminergic properties suggesting its potential usefulness as a neuroleptic.     

M&B 28,767: a potent anti-secretory and anti-ulcer PG analogue. A comparative study with 16, 16' dimethyl PGE2 methylester

M&B 28,767 [(+/-)11-deoxy-16-phenoxy-omega-tetranor PGE1] and 16, 16'-dimethyl PGE2 methylester (DMPG) were compared for their effects on gastric acid secretion (GAS) and gastric ulceration (GU), employing various laboratory models. In anaesthetised rats, GAS was stimulated by a continuous i.v. infusion of pentagastrin (30 micrograms/kg/h), and PG analogues were perfused through the stomach for 1 h. M&B 28,767 (3-15 micrograms/kg/h) and DMPG (3-60 micrograms/kg/h) reduced GAS in a dose-related manner, the ED50 values being 4 and 15 micrograms/kg/h respectively. In conscious rats possessing indwelling gastric cannulae, oral doses of M&B 28,767 (0.025-0.1 microgram/kg) and DMPG (0.50-1.0 microgram/kg) caused a prolonged inhibition of pentagastrin-stimulated GAS. M&B 28,767 was 17 times more potent than DMPG; the respective ED50 values were 0.036 and 0.6 microgram/kg. Indomethacin-induced ulceration in rats, was reduced by both M&B 28,767 and DMPG; the respective ED50 values being 3.0 and 0.8 micrograms/kg. Both compounds given orally increased gastrointestinal motility in mice; M&B 28,767 (1-3 mg/kg) and DMPG (0.1-0.3 mg/kg) caused diarrhoea, the former being about 0.1 times as potent as the latter. In another test, M&B 28,767 (0.5-5.0 mg/kg) and DMPG (10-40 micrograms/kg) overcame morphine-induced constipation in a dose-related manner, the respective ED50s being 0.9-1.4 mg/kg and 20-40 micrograms/kg. Thus, M&B 28,767 had a better profile of activity than DMPG as an antisecretory and antiulcer agent.     

Evaluation of the racemate and the enantiomers of a new highly active and selective aromatase inhibitor of the aminoglutethimide type.

Compound 1 [3-(4-aminophenyl)-3-cyclohexylpiperidine-2,6-dione] is a highly potent nonsteroidal aromatase inhibitor of the aminoglutethimide (AG)-type containing an asymmetric carbon atom. 1 and its enantiomers (+)-1 and (-)-1 inhibited human placental aromatase by 50% at 0.3, 0.15, and 4.6 microM, respectively (IC50 AG = 37 microM). A competitive type of inhibition was observed for 1 and (+)-1 (Ki 1 = 3.9 nM, Ki (+)-1 = 2.0 nM, Ki AG = 408 nM). Using solubilized high spin aromatase, 1 showed a type II difference spectrum indicating the interaction of the amino nitrogen with the central Fe(III)-ion of the cytochrome P450 heme component. 1 and (+)-1 inhibited cholesterol side chain cleavage enzyme (desmolase) by 50% at 67 and 82 microM, respectively (IC50 AG = 29 microM). In ACTH-stimulated rat adrenal tissue in vitro, 1 was less active in inhibiting aldosterone and corticosterone production compared to AG (IC50s, 1, 130 and 140 microM, AG, 80 and 50 microM, respectively). In vivo, 1 was superior to AG, too: it showed a stronger inhibition of the plasma estradiol concentration of pregnant mares' serum gonadotropin-primed SD rats, the activity residing mainly in the (+)-enantiomer [ovarian vein: (+)-1, 0.31 mg/kg: 81% inhibition, (-)-1, 0.31 mg/kg: 6%, AG, 1.25 mg/kg: 35%]. Furthermore 1 was much more active in inhibiting the testosterone-stimulated tumor growth of the ovariectomized 9,10-dimethyl-1,2-benzanthracene tumor-bearing SD rat (postmenopausal model). Up to a dose of 600 mg/kg of 1 no central nervous symptom depressive effects were observed in the motility test and the rotarod experiment, whereas AG exhibited ED50s of 62 and 164 mg/kg, respectively.     

In vitro and in vivo opioid activity of [DPro(6)]dermorphin,a new dermorphin analogue

To study the effects of inducing stereo-chemical modifications in the structure of dermorphin (DM) so as to improve its mu-opioid receptor affinity and its resistance to C-terminal enzymatic degradation, in the Institute of Molecular Genetics of Moscow, we synthesized a new DM analogue ([DPro(6)]DM) and analyzed the changes induced in the biological activities of DM by substituting the Pro(6) residue with DPro(6). We compared the activity of the new DM analogue and DM in in vitro assays and in in vivo tests of analgesia, thermoregulation, heart rate recordings, and gastrointestinal motility in rats. In the in vitro tests, guinea pig ileum (GPI) and mouse vas deferens (MVD), although the opioid activities of [DPro(6)]DM indicated that the peptide was always less potent than DM, its lower IC(50) ratios (mu/delta) showed that it had higher mu-opioid receptor selectivity. In the in vivo analgesic test, [DPro(6)]DM, when injected intraperitoneally (i.p.) (0.5-5 and 10mg/kg) in rats, had the same antinociceptive efficacy as DM and when injected intranasally (i.n.) (0.005 and 0.02 mg/kg) it induced a more stable and long-lasting analgesia than DM (the AUC was about 91% higher for [DPro(6)]DM than for DM). Moreover, these data confirm that the intranasal route is advantageous for peripheral drug administration. In the heart rate study, [DPro(6)]DM and DM (0.5mg/kg, i.p.), induced a similar, weak bradycardia. The only difference was that [DPro(6)]DM induced a longer-lasting effect than DM. Conversely, in body temperature regulation [DPro(6)]DM induced weaker inhibitory activity than DM (56% of the DM-induced response); it did so only in a cold environment and at the maximal used dose (0.5mg/kg, i.p.) without inducing vasomotor effects. In the gastrointestinal study, [DPro(6)]DM and DM (0.005, 0.05, and 0.5mg/kg, i.p.) significantly slowed upper gastrointestinal transit of a charcoal meal and inhibited colonic propulsion. Comparison of the ED(50) values of [DPro(6)]DM (0.03 mg/kg) and DM (0.009 mg/kg) showed that the DM analogue was about three times less potent than DM in slowing gastrointestinal and colonic transit. In conclusion, all these data overall suggest that structural maneuvering in the Pro(6)-residue of the DM molecule changes its affinity for mu-opioid receptor subtypes and confirms the usefulness of experimental studies involving structural modifications in obtaining new therapeutic agents.     

Analgesic activity of spiradoline mesylate (U-62,066E), a kappa opioid agonist in mice

The present study was undertaken to evaluate the analgesic potency of spiradoline mesylate, a k(kappa) opioid agonist, in comparison with that of morphine, by hot plate, tail-pinch and acetic acid-induced writhing assay. The ED50 values of spiradoline in hot plate, tail-pinch and acetic acid-induced writhing assay were 0.46, 0.26 and 0.20 mg/kg, respectively. The analgesic potency of spiradoline was 1.5-7.0 times higher than that of morphine. Repeated treatment with spiradoline as well as morphine developed tolerance to the analgesic effect in hot plate assay. In mice developed tolerance to one analgesic, response to the other analgesic did not alter compared to saline-treated mice. Single administration of spiradoline (1.5 and 3 mg/kg, s.c.) did not inhibit morphine-induced analgesia. These results suggest that spiradoline has more potent analgesic activity than morphine, presumably mediated through stimulation of receptors different from morphine.     

The human renin infused rat: use as an in vivo model for the biological evaluation of human renin inhibitors

The human renin infused rat model (HRIRM) was used as an in vivo small-animal model for evaluating the efficacy of a collection of inhibitors of human renin. The intravenous infusion of recombinant human renin (2.4 microg x kg(-1) x min(-1)) in the ganglion-blocked, nephrectomized rat produced a mean blood pressor response of 47+/-3 mm Hg (1 mm Hg = 133.3 Pa), which was reduced by captopril, enalkiren, and losartan in a dose-dependent manner following oral administration, with ED50 values of 0.3+/-0.1, 2.5+/-0.9, and 5.2+/-1.6 mg/kg, respectively. A series of peptidomimetic P2-P3 butanediamide renin inhibitors inhibited purified recombinant human renin in vitro in a concentration-dependent manner, with IC50 values ranging from 0.4 to 20 nM at pH 6.0, with a higher range of IC50 values (0.8-80 nM) observed at pH 7.4. Following i.v. administration of renin inhibitors, the pressor response to infused human renin in the HRIRM was inhibited in a dose-dependent manner, with ED50 values ranging from 4 to 600 microg/kg. The in vivo inhibition of human renin following i.v. administration in the rat correlated significantly better with the in vitro inhibition of human renin at pH 7.4 (r = 0.8) compared with pH 6.0 (r = 0.5). Oral administration of renin inhibitors also resulted in a dose-dependent inhibition of the pressor response to infused human renin, with ED50 values ranging from 0.4 to 6.0 mg/kg and the identification of six renin inhibitors with an oral potency of <1 mg/kg. The ED50 of renin inhibitors for inhibition of angiotensin I formation in vivo was highly correlated (r = 0.9) with the ED50 for inhibition of the pressor response. These results demonstrate the high potency, dose dependence, and availability following oral administration of the butanediamide series of renin inhibitors.     

The spinal antinociceptive effect of FR140423 is mediated through kyotorphin receptors

We investigated the antinociceptive effect of a novel anti-inflammatory and analgesic drug, 3-(difluoromethyl)-1-(4-methoxyphenyl)-5-[4-(methylsulfinyl)phenyl]pyraz ole (FR140423), in the tail-pinch test in mice, and evaluated the mechanism of action of FR140423 using L-leucyl-L-arginine (Leu-Arg), a kyotorphin (endogenous Met-enkephalin releaser) receptor antagonist, L-NG-nitroarginine methylester (L-NAME), an inhibitor of nitric oxide (NO) synthase, and methylene blue (MB), an inhibitor of activation of guanylate cyclase. Oral administration of FR140423, at doses of 5-80 mg/kg, produced a dose-dependent antinociceptive effect with an ED50 value of 18 mg/kg. This antinociception was reversed by intrathecal (i.t.) (10 microg/mouse), but not by intracerebroventricular (i.c.v.) (100 microg/mouse), injection of Leu-Arg. Moreover, the antinociceptive effect of i.t. injection of FR140423 with an ED50 value of 3.7 microg/mouse was completely antagonized by co-administered Leu-Arg 10 microg/mouse. However, L-NAME (2000 mg/kg s.c.) and MB (200 mg/kg s.c.) did not antagonize the antinociception of FR140423. These findings suggest that FR140423 plays a role in nociceptive modulation in the spinal cord, being antinociceptive via the kyotorphin-Met-enkephalin pathway but not via the peripheral NO-cyclic GMP pathway.     

Characterization of the effects of opiorphin and sialorphin and their analogs substituted in position 1 with pyroglutamic acid on motility in the mouse ileum

Opiorphin and sialorphin are two recently discovered endogenous enkephalin‐degrading enzyme inhibitors. Our aim was to characterize their effect on the mouse ileum motility and to investigate the role of glutamine in position 1. Opiorphin, sialorphin, and their analogs substituted in position 1 with pyroglutamic acid (pGlu) were synthesized by the solid‐phase method using Fmoc chemistry. The effect of peptides on gastrointestinal (GI) motility was characterized using in vitro assays and in mouse model of upper GI transit. Opiorphin and sialorphin, but not their analogs, significantly increased electrical field‐stimulated contractions in the mouse ileum in a δ‐opioid receptor‐dependent manner. Opiorphin, sialorphin, and their analogs did not influence the effect of [Met⁵]enkephalin on smooth muscle contractility in the mouse ileum in vitro. [Met⁵]enkephalin and sialorphin, but not opiorphin injected intravenously (1 mg/kg), significantly inhibited the upper GI transit. The intraperitoneal administration of peptides (3 mg/kg) did not change the mouse upper GI transit. In conclusion, this is the first study investigating the effect of opiorphin and sialorphin on the mouse ileum motility and demonstrating that glutamine in position 1 is crucial for their pharmacological action. Our results may be important for further structure–activity relationship studies on opiorphin and sialorphin and future development of potent clinical therapeutics aiming at the enkephalinergic system. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Antagonism of peptidoleukotrienes and inhibition of systemic anaphylaxis by RG 12525 in guinea pigs

RG 12525 was determined to be a specific, competitive and orally effective antagonist of the peptidoleukotrienes, LTC4, LTD4 and LTE4, in several assays utilizing guinea pigs. In vitro, RG 12525 competitively inhibited 3H-LTD4 binding to lung membranes (Ki = 3.0 +/- 0.3 nM) and competitively antagonized the spasmogenic activity of LTC4, LTD4 and LTE4 on lung strips (KB values = 3 nM) with greater than 8000 fold selectivity. In vivo, RG 12525 orally inhibited LTD4 induced wheal formation (ED50 = 5 mg/kg with a t1/2 = 10 hrs at 9 mg/kg), LTD4 induced bronchoconstriction (ED50 = 0.6 mg/kg), and anaphylactic death (ED50 = 2.2 mg/kg with a t1/2 = 7 hrs at 10 mg/kg) and antigen induced bronchoconstriction (ED50 = 0.6 mg/kg). RG 12525 represents a significant improvement in receptor affinity and oral efficacy and thus, is a valuable pharmacological tool to evaluate peptidoleukotrienes in allergic diseases.     

Stimulation of prolactin secretion by morphine: role of the central serotonergic system.

Unanesthetized male rats with indwellinh right atrial cannulae were injected with morphine (MOR) i.v. which produced a dose-related increase in plasma prolactin levels (PRL). This effect was blocked partially by naloxone (NAL) at a dose of 0.06 mg/kg and totally by 0.6 mg/kg NAL. Interruption of central serotonergic neurotransmission by receptor blockade, with metergoline (MET) or cyproheptadine (Cypro), inhibition of tryptophan hydroxylase by para-chlorophenylalanine or destruction of serotonin neurons by 5, 7-dihydroxytryptamine antagonized the morphine (3 mg/kg) induced elevation in PRL release. Depression of dopaminergic activity with α-methyl-para-tyrosine elevated the basal PRL levels, but it did not prevent a further increase of prolactin levels by morphine (3 mg/kg). These data are compatible with the hypothesis that morphine stimulates PRL release by activation of the central serotonergic system.     

Novel 8 alpha-ergolines with inhibitory and stimulatory effects on prolactin secretion in rats

Four derivatives of the ergot dopamine (DA) agonist lisuride (LIS), namely 6-n-propyl-lisuride (6-n-propyl-LIS), transdihydrolisuride (TDHL), 6-n-propyl-transdi-hydrolisuride (6-n-propyl-TDHL) and 2-bromolisuride (2-Br-LIS) were investigated in female rats with regard to their influence on hyperprolactinaemia induced by pretreatment with reserpine (2 mg/kg i.p., 24 h) at various intervals following their subcutaneous or oral administration (0.05 mg/kg). Two hours after administration, LIS, 6-n-propyl-LIS, and 6-n-propyl-TDHL caused a statistically significant inhibition of reserpine-induced hyperprolactinaemia of about the same extent. Eight hours after administration 6-n-propyl-LIS and 6-n-propyl-TDHL were as active as after 2 h in inhibiting prolactin (PRL) secretion whereas LIS was almost ineffective in this respect. TDHL caused a statistically significant inhibition of PRL secretion at 2 and 8 h after oral administration; this effect was less pronounced after s.c. administration. In contrast to the aforementioned derivatives 2-Br-LIS further increased the reserpine-induced hyperprolactinaemia. In normal male rats pretreatment with 2-Br-LIS (0.025-6.25 mg/kg s.c., 2 h) dose-dependently stimulated PRL secretion. The present data support the assumption of the longlasting DA agonistic action of 6-n-propyl-LIS and 6-n-propyl-TDHL and of the antidopaminergic properties of 2-Br-LIS recently derived from behavioural studies.     

The spinal antinociceptive effect of FR140423 in mice involvement of the descending noradrenergic and serotonergic systems.

In this study, we investigated the role of descending monoaminergic systems in the antinociceptive activity of FR140423, 3-(difluoromethyl)-1-(4-methoxyphenyl)-5-[4-(methyl sulfinyl)phenyl]pyrazole, by using the tail-pinch test in mice and various monoamine depletors. The antinociceptive effects of FR140423 given p.o. and i.t. with ED50 values of 22 mg/kg and 3.5 microg/mouse, respectively, in the tail-pinch test were antagonized by reserpine, 6-hydroxydopamine plus nomifensine, and p-chlorophenylalanine treatment, whereas the antinociceptive action of morphine in this assay was attenuated by reserpine and 6-hydroxydopamine plus nomifensine but not by p-chlorophenylalanine treatment. These results suggest that both descending noradrenergic and serotonergic systems are involved in the antinociceptive activity of spinally and systemically administered FR140423 against mechanical noxious stimuli. The mechanisms underlying the suppressive action of FR140423 on the nociceptive response may differ from those of morphine in mice.     

Effects of copper source and concentration on copper status and immune function in growing and finishing steers

Forty-eight individually fed purebred Angus steers (7±1.1 mo of age, 218±9.1 kg BW) were used to determine the effects of copper (Cu) source and concentration on Cu status and immune function. Steers were stratified by weight and initial liver Cu concentration and randomly assigned to one of five treatments. Treatments were: (1) control (no supplemental Cu), (2) 10 mg Cu/kg dry matter (DM) from Cu sulfate (CuSO₄), (3) 10 mg Cu/kg DM from a Cu-amino acid complex (Availa Cu; Zinpro Corporation, Eden Prairie, MN, USA), (4) 20 mg Cu/kg DM from CuSO₄, and (5) 20 mg Cu/kg DM from Availa Cu. Steers were housed in individual pens and fed an alfalfa-corn based growing diet (7.1 mg Cu/kg DM) for 56 d then gradually switched to a high concentrate diet (6.1 mg Cu/kg DM) for 144 d. On d 56 of the growing phase and d 112 of the finishing phase, liver Cu concentrations were higher (P<0.01) in Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P<0.01) liver Cu concentrations than steers receiving 10 mg Cu/kg DM. On d 112 of the finishing phase, steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P<0.01) liver Cu concentrations than steers supplemented 20 mg Cu/kg DM from CuSO₄. Cell mediated immune response to phytohemagglutinin was higher (P<0.01) in steers supplemented with 20 mg Cu/kg DM compared to steers supplemented with 10 mg Cu/kg DM. Total immunoglobulin (Ig) and immunoglobulin G (IgG) concentrations specific to pig red blood cells (PRBC) were higher (P<0.01) in steers supplemented with 10 mg Cu/kg DM from CuSO₄ than steers supplemented with 10 mg Cu/kg DM from Availa Cu. During the finishing phase, IgG concentrations specific to PRBC were higher (P<0.03) and antibody titers specific to ovalbumin (OVA) were lower (P<0.05) in control steers relative to Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P<0.02) antibody titers specific to OVA than steers receiving 10 mg Cu/kg DM. Steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P<0.01) antibody titers specific to OVA than steers supplemented with 20 mg Cu/kg DM from CuSO₄. Results indicate that the immune response to an antigen varies depending on the type of antigen administered as well as the concentration and source of Cu supplemented.     

Biological characterization of 10-(2-propynyl) estr-4-ene-3, 17-dione (MDL 18,962), an enzyme-activated inhibitor of aromatase

MDL 18,962 was shown to be a highly specific, potent (Ki = 3-4 nM), enzyme-activated inhibitor of aromatase with minimal intrinsic endocrine properties. The affinity of MDL 18,962 was higher for human and baboon placental aromatase than for rhesus placental or rodent ovarian aromatase. These species differences necessitated the development of a novel model of peripheral aromatase utilizing human enzyme. Human choriocarcinoma trophoblast xenografts in athymic nude mice were used for pharmacologic and pharmacokinetic evaluation of MDL 18,962. The ED50 for inhibition of aromatase activity in these trophoblast tumors at 6 h post-treatment was 1.4 mg/kg, s.c. and 3.0 mg/kg, oral. Preliminary results indicated that the ED50 for inhibition of peripheral aromatization of androgen by MDL 18,962 in female baboons was 0.01 mg/kg, i.v. and 4 mg/kg, oral.     

Interaction of antidepressants with 4-aminopyridine.

Systemic administration of 4-Aminopyridine at a dose of 4 mg/kg (4-AP) induces hypothermia in mice. Scopolamine (ED50 = 0.26 mg/kg) and two tricyclic antidepressants, desipramine (ED50 = 1.82 mg/kg) and IM/P/3/4 (ED50 = 8.95 mg/kg) completely antagonize 4-AP-induced hypothermia, whereas minaprine (0.1-0.25 mg/kg), a non-tricyclic antidepressant, reverts only 45% of the maximal effect of 4-AP. Oxotremorine at a dose of 0.05 mg/kg (OXO) induces a hypothermic effect comparable to that of 4-AP. Scopolamine (ED50 = 0.011 mg/kg) completely reverts OXO-induced hypothermia whereas desipramine and IM/P/3/4 never produce more than 60% of antagonism over a wide range of doses. Minaprine does not affect OXO-induced hypothermia. These results suggest that the interaction of antidepressants with cholinergic function occurs mainly at the pre-synaptic level.     

The anticonvulsant activities of N-benzyl 3-methoxypropionamides

We recently reported that the ED50 value for (R,S)-2,3-dimethoxypropionamide (1) in the maximal electroshock (MES)-induced seizure test in mice was 30 mg/kg (Choi, D.; Stables, J.P., Kohn, H. Bioorg. Med. Chem. 1996, 4, 2105). This value is comparable to that observed for phenobarbital (ED50 = 22 mg/kg). Compound 1 is structurally similar to a class of MES-selective anticonvulsant agents, termed functionalized amino acids (2), that were developed in our laboratory. The distinguishing feature of 2 is the differential activities observed for enantiomers. In this study, we asked whether comparable differences in activities were observed in the MES-induced seizure test for (R)- and (S)-1. We developed stereospecific syntheses for these enantiomers and showed that both compounds exhibit nearly equal anticonvulsant activity in mice (i.p.) (MES ED50 = 79-111 mg/kg). The surprisingly high ED50 values for (R)- and (S)-1 required our redetermining the ED50 value for (R,S)-1. We revised this value to 79 mg/kg. A limited structure-activity relationship study for 1 was conducted. Special attention was given to the C(2) methoxy unit in 1. We found that replacement of this moiety led to only modest differences in the MES activities upon ip administration to mice. Significantly, we observed an enhancement in the anticonvulsant activity for (R,S)-N-benzyl 2-hydroxy-3-methoxypropionamide ((R,S)-6) upon oral administration to rats ((R,S)-6: mice (i.p.) ED50 > 100, < 300 mg/kg; rat (oral) ED50 = 62 mg/kg). The activities of 3-methoxypropionamides, functionalized amino acids, and related compounds are discussed.     

Anticonvulsant activity of 2,4(1H)-diarylimidazoles in mice and rats acute seizure models

2,4(1H)-Diarylimidazoles have been previously shown to inhibit hNa(V)1.2 sodium (Na) channel currents. Since many of the clinically used anticonvulsants are known to inhibit Na channels as an important mechanism of their action, these compounds were tested in two acute rodent seizure models for anticonvulsant activity (MES and scMet) and for sedative and ataxic side effects. Compounds exhibiting antiepileptic activity were further tested to establish a dose response curve (ED(50)). The experimental data identified four compounds with anticonvulsant activity in the MES acute seizure rodent model (compound 10, ED(50)=61.7mg/kg; compound 13, ED(50)=46.8mg/kg, compound 17, ED(50)=129.5mg/kg and compound 20, ED(50)=136.7mg/kg). Protective indexes (PI=TD(50)/ED(50)) ranged from 2.1 (compound 10) to greater than 3.6 (compounds 13, 17 and 20). All four compounds were shown to inhibit hNa(V)1.2 in a dose dependant manner. Even if a correlation between sodium channel inhibition and anticonvulsant activity was unclear, these studies identify four Na channel antagonists with anticonvulsant activity, providing evidence that these derivatives could be potential drug candidates for development as safe, new and effective antiepileptic drugs (AEDs).     

Postprandial Hypertriglyceridemia Predicts Development of Insulin Resistance Glucose Intolerance and Type 2 Diabetes

Insulin resistance (IR) and type 2 diabetes mellitus (T2DM) have been found to be associated with postprandial hypertriglyceridemia (PPHTg). However, whether PPHTg can cause IR and diabetes is not clear. We therefore investigated the role of PPHTg in development of T2DM in rat model of T2DM. 96 male Wistar rats were randomized into four groups (24 rats each). Control Group A, high sucrose diet (HSD) Group B, HSD+Pioglitazone (10mg/kg/day) Group C and HSD+Atorvastatin (20mg/kg/day) Group D. Fat and glucose tolerance tests were done at regular intervals in all groups besides insulin and body weight measurement. At 26 weeks, low dose streptozotocin (15mg/kg,i.p.) was given to half of the rats. All rats were followed up till 48 weeks. PPHTg developed as early as week 2 in Group B and stabilized by week 14. Group B displayed highest PPHTg compared to other groups. Atorvastatin treatment (Group D) abolished PPHTg which became comparable to controls, pioglitazone treatment partially blunted PPHTg resulting in intermediate PPHTg. Group B with highest PPHTg showed highest subsequent IR, glucose intolerance (GI) and highest incidence of prediabetes at week 26 and diabetes at week 34 and 46 compared to other groups. Group D rats displayed lower IR, GI, low incidence of prediabetes and diabetes at these time points compared to Groups B and C. ROC analysis showed that triglyceride area under the curve of each time point significantly predicts the risk of diabetes. Present study provides the evidence that PPHTg predicts the development of IR, GI and T2DM in rat model of diet induced T2DM.     

Mechanisms for the stimulatory effects of opioidergic and serotonergic input signals on prolactin in pregnant rats.

Dopamine (DA) neurons participate in tonic inhibition of prolactin (PRL), whereas beta-endorphin (beta-End) and serotonin (5-HT) neurons appear to be important stimulatory links for nocturnal PRL surges that occur throughout the first half of pregnancy in the rat. The purpose of this study was to determine how these neuronal components might be organized within the pathway controlling PRL release during gestation. Maximal stimulation of DA receptors with the agonist bromocriptine mesylate (Bromo) completely blocked the PRL response to beta-End (100 ng/microliters/min for 15 min) given intracerebroventricularly (i.c.v.) on day 8 of pregnancy. DA receptor blockade, produced by implanting a 25 mg pellet of haloperidol (Hal) on day 7 of pregnancy, resulted in PRL levels of 500-600 ng/ml by the following morning. beta-End i.c.v. or 250 mg/ml/kg BW of the DA synthesis inhibitor, alpha-methyl-p-tyrosine (alpha-MPT), given during the intersurge period, were equally effective in significantly increasing PRL (p less than 0.01) above pretreatment levels. beta-End and alpha-MPT evoked similar increases in rats pretreated with Hal, suggesting the stimulatory effect of beta-End on nocturnal PRL surges may primarily be due to DA inhibition. The next objective was to determine how beta-End and 5-HT might interact to stimulate the nocturnal surge. Day 8 pregnant rats were infused continuously with the opioid receptor blocker, naloxone hydrochloride (Nal), at a rate of 2.0 mg/10 min from 1000-1300 h. The PRL response to an injection of 20 mg/kg BW 5-hydroxytryptophan (5-HTP) at 1200 h was greatly attenuated, compared to controls infused with saline instead of Nal. This suggests that 5-HT stimulates PRL, at least in part, by an action at opioid receptors. Distilled H2O or 10 mg/kg BW of the selective S2 receptor blocker, ketanserin tartrate (Ket), was given intraperitoneally (i.p.) during the intersurge period on day 8 of pregnancy. All animals demonstrated an identical response to beta-End given 2 hours later, regardless of the type of pretreatment. It appears that beta-End does not stimulate PRL by way of an S2 receptor. Although beta-End induced a significant increase in PRL on day 16 of pregnancy, the response was attenuated by more than 60% compared to the response on day 8 of pregnancy. This attenuation may involve placental lactogens, shown to be secreted during this time and to inhibit PRL secretion.(ABSTRACT TRUNCATED AT 400 WORDS)     

Concentration-dependent interaction of theophylline with d-tubocurarine

The interaction of theophylline with d-tubocurarine chloride (dTC) was examined in rabbits. After steady-state subtherapeutic (less than 10 mg/l), therapeutic (10-20 mg/l), and toxic (greater than 20 mg/l) concentrations of theophylline, dose-response curves for dTC were determined and compared with controls that received no theophylline. At therapeutic concentrations of theophylline the effective dose for 50% inhibition of twitch (ED50) for dTC (mean +/- SE, 0.115 +/- 0.016 mg/kg) was significantly shifted to the left in comparison with the control (0.165 +/-0.008 mg/kg). The ED50 of dTC for the subtherapeutic group was 0.143 +/- 0.011 mg/kg, which was less than the control but not of statistical significance (P = 0.1). The ED50 for the toxic theophylline group was 0.168 +/- 0.003 mg/kg, which was not significantly different from controls but significantly different from the theophylline therapeutic and subtherapeutic groups. Thus, toxic concentrations of theophylline reversed the potentiating effects of therapeutic and subtherapeutic concentrations of dTC dose-response curves. Therefore, depending on concentration, theophylline exhibits a biphasic interaction with dTC. Surgical patients on theophylline may require less dTC intraoperatively. More importantly, the use of theophylline in the postoperative period to reverse anesthetic effects may result in recurarization.