EGCG Suppresses ERK5 Activation to Reverse Tobacco Smoke-Triggered Gastric Epithelial-Mesenchymal Transition in BALB/c Mice

Tobacco smoke is an important risk factor of gastric cancer. Epithelial-mesenchymal transition is a crucial pathophysiological process in cancer development. ERK5 regulation of epithelial-mesenchymal transition may be sensitive to cell types and/or the cellular microenvironment and its role in the epithelial-mesenchymal transition process remain elusive. Epigallocatechin-3-gallate (EGCG) is a promising chemopreventive agent for several types of cancers. In the present study we investigated the regulatory role of ERK5 in tobacco smoke-induced epithelial-mesenchymal transition in the stomach of mice and the preventive effect of EGCG. Exposure of mice to tobacco smoke for 12 weeks reduced expression of epithelial markers E-cadherin, ZO-1, and CK5, while the expression of mesenchymal markers Snail-1, Vimentin, and N-cadherin were increased. Importantly, we demonstrated that ERK5 modulated tobacco smoke-mediated epithelial-mesenchymal transition in mice stomach, as evidenced by the findings that tobacco smoke elevated ERK5 activation, and that tobacco smoke-triggered epithelial-mesenchymal transition was reversed by ERK5 inhibition. Treatment of EGCG (100 mg/kg BW) effectively attenuated tobacco smoke-triggered activation of ERK5 and epithelial-mesenchymal transition alterations in mice stomach. Collectively, these data suggested that ERK5 was required for tobacco smoke-triggered gastric epithelial-mesenchymal transition and that EGCG suppressed ERK5 activation to reverse tobacco smoke-triggered gastric epithelial-mesenchymal transition in BALB/c mice. These findings provide new insights into the mechanism of tobacco smoke-associated gastric tumorigenesis and the chemoprevention of tobacco smoke-associated gastric cancer.

Nanosuspension for improving the bioavailability of a poorly soluble drug and screening of stabilizing agents to inhibit crystal growth

The purpose of this study was to develop a nanosuspension of a poorly soluble drug by nanomilling process using wet media milling to achieve superior in vitro dissolution and high in vivo exposure in pharmacokinetic studies. A promising nanosuspension was developed with Vitamin E TPGS based formulation with particle size in the nano range. Although the formulation showed significant improvement during in vitro dissolution and in vivo plasma level, probably due to the strong hydrophobic interaction between Vitamin TPGS and the drug molecule, crystal growth was observed during stability studies. A systematic study was done with different combinations of solubilizer/stabilizer system in order to obtain a more stable nanosuspension. Hydroxypropyl methylcellulose (HPMC 3 cps) was found to stabilize the nanosuspension by better surface coverage due to stronger interaction with the drug as compared to other stabilizers used in this study.

Self-administration of bretazenil under progressive-ratio schedules: behavioral economic analysis of the role intrinsic efficacy plays in the reinforcing effects of benzodiazepines

Previous research suggests that intrinsic efficacy of benzodiazepines is an important determinant of their behavioral effects. We evaluated the reinforcing effects of the benzodiazepine partial agonist bretazenil using behavioral economic models referred to as "consumer demand" and "labor supply". Four rhesus monkeys were trained under a progressive-ratio (PR) schedule of i.v. midazolam injection. A range of doses of bretazenil (0.001-0.03 mg/kg/injection and vehicle) was evaluated for self-administration with an initial response requirement of 40 that doubled to 640; significant self-administration was maintained at doses of 0.003-0.03 mg/kg/injection. Next, a dose of bretazenil that maintained peak injections/session was made available with initial response requirements doubling from 10 to 320 (maximum possible response requirements of 160 and 5120, respectively), and increasing response requirements decreased self-administration (mean number of injections/session) of a peak dose (0.01 mg/kg/injection). Analyses based on consumer demand revealed that a measure of reinforcing strength termed "essential value", for bretazenil was similar to that previously obtained with midazolam (non-selective full agonist), but less than that observed for zolpidem (full agonist, selective for α1 subunit-containing GABA(A) receptors). According to labor supply analysis, the reinforcing effects of bretazenil were influenced by the economic concept referred to as a "price effect", similar to our previous findings with midazolam but not zolpidem. In general, behavioral economic indicators of reinforcing effectiveness did not differentiate bretazenil from a non-selective full agonist. These findings raise the possibility that degree of intrinsic efficacy of a benzodiazepine agonist may not be predictive of relative reinforcing effectiveness.

Allosteric modulation by benzodiazepines of GABA-gated chloride channels of an identified insect motor neurone

The actions of benzodiazepines were studied on the responses to GABA of the fast coxal depressor (D(f)) motor neurone of the cockroach, Periplaneta americana. Ro5-4864, diazepam and clonazepam were investigated. Responses to GABA receptors were enhanced by both Ro5-4864 and diazepam, whereas clonazepam, a potent-positive allosteric modulator of human GABA(A) receptors, was ineffective on the native insect GABA receptors of the D(f) motor neurone. Thus, clear pharmacological differences exist between insect and mammalian native GABA-gated chloride channels with respect to the actions of benzodiazepines. The results enhance our understanding of invertebrate GABA-gated chloride channels which have recently proved important in (a) comparative studies aimed at identifying human allosteric drug-binding sites and (b) understanding the actions of compounds used to control ectoparasites and insect crop pests.

Contribution of specific binding to the central benzodiazepine site to the brain concentrations of two novel benzodiazepine site ligands

The in vivo occupancy of brain benzodiazepine binding sites by compounds A and B was measured using a [(3)H]Ro 15-1788 binding assay and related to plasma and brain drug concentrations. The plasma concentration associated with 50% occupancy was higher for compound A than compound B (73 and 3.7 nM, respectively), however, there was little difference in the brain concentrations required (73 and 63 nM). Both compounds showed a non-linear relationship between plasma and brain concentrations such that above brain concentrations of approximately 100 nM increasing plasma concentrations did not result in a concomitant increase in brain concentrations. This is consistent with brain concentrations being dependent on a saturable compartment which was postulated to be the benzodiazepine binding site-containing GABA(A) receptors. This hypothesis was tested in alpha1H101R mice, in which the alpha1 subunit of the GABA(A) receptor is rendered insensitive to benzodiazepine binding resulting in an approximate 50% reduction in the total benzodiazepine-containing GABA(A) receptor population. It was shown that the Occ(50) brain concentrations in the alpha1H101R animals was lower (17 nM) than in wild type mice (63 nM), as was the plateau concentration in the brain (105 and 195 nM, respectively). These data suggest measured concentrations of compounds A and B in brain tissue are dependent on receptor expression with a minimal contribution from unbound and non-specifically bound compound.

Effect of Z-360, a novel orally active CCK-2/gastrin receptor antagonist on tumor growth in human pancreatic adenocarcinoma cell lines in vivo and mode of action determinations in vitro

PURPOSE

Gastrin is known to enhance the growth of pancreatic carcinoma via the cholecystokinin (CCK)-2/gastrin receptor. We investigated the anti-tumor effect of Z-360 (calcium bis [(R)-(-)-3-[3-{5-cyclohexyl-1-(3,3-dimethyl-2-oxo-butyl)-2-oxo-2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepin-3-yl}ureido]benzoate]), a novel orally active CCK-2 receptor antagonist alone or combined with the chemotherapeutic agent, gemcitabine in human pancreatic adenocarcinoma cell lines.

RESULTS

Z-360 potently inhibited specific binding of [3H]CCK-8 to the human CCK-2 receptor, with a Ki value of 0.47 nmol/l, and showed antagonistic activity for this receptor. The anti-tumor effect of Z-360 alone or combined with gemcitabine was assessed using subcutaneous xenografts of MiaPaCa2 and PANC-1 and an orthotopic xenograft model (PANC-1). Oral administration of Z-360 significantly inhibited the growth of MiaPaCa2 (41.7% inhibition at 100 mg/kg, P<0.01). Combined administration of Z-360 and gemcitabine significantly inhibited subcutaneous PANC-1 tumor growth compared with either agent alone (27.1% inhibition compared to effect with gemcitabine, P<0.05), and significantly prolonged survival compared with the vehicle control (median survival of 49 days in vehicle compared to 57 days in the combination group, P<0.05). In vitro studies showed that Z-360 significantly inhibited gastrin-induced proliferation of human CCK-2 receptor-expressing cells, and also significantly reduced gastrin-induced PKB/Akt phosphorylation to the level of untreated controls.

CONCLUSION

In the present study, we have shown that Z-360 combined with gemcitabine can inhibit pancreatic tumor growth and prolong survival in a pancreatic carcinoma xenograft model, on a possible mode of action being the inhibition of gastrin-induced PKB/Akt phosphorylation through blockade of the CCK-2 receptor. Our results suggest that Z-360 may be a useful adjunct to gemcitabine for the treatment of pancreatic carcinoma and a therapeutic option for patients with advanced pancreatic cancer.

Mediators of glucagon-like peptide 2-induced blood flow: responses in different vascular sites

The aims of the present study were: to characterize the mechanisms of hemodynamic alterations induced by GLP-2, and, to compare the responses elicited in the superior mesenteric artery (SMA) to other vascular beds. Anesthetized rats were infused at the doses of 0.9, 2.3, 4.6 and 9.3 nmol/kg into the jugular vein for 60 min. Blood flow in the various arteries was measured by the ultrasonic transit time technique. Some animals were pretreated with indomethacin (5 mg/kg, ip), L-NAME (9, 18, 36 and 72 micromol/kg, iv), atropine sulfate (1-2 mg/kg, iv), CCK-1 and CCK-2 receptor antagonists (L-364,718 and L-365,260, 1 mg/kg, iv), exendin (9-39) amide (35 nmol/kg, iv) and lidocaine (74 micromol/kg, iv) prior to the infusion of GLP-2 (4.6 nmol/kg). In another group, capsaicin was applied either systematically (125 mg/kg, sc) or vagally (1 mg/rat). GLP-2 administration at all doses significantly increased the SMA blood flow throughout the experiments. GLP-2 (4.6 nmol/kg) infusion significantly increased blood flow of inferior mesenteric artery and carotid artery but not in any other vessel measured. Only the pretreatments with L-NAME and lidocaine were ineffective in preventing the GLP-2-induced responses. These results implicate that GLP-2-induced blood flow alterations are most significant in the SMA and are not mediated by prostaglandins, muscarinic, GLP-1 or CCK receptors. Our results also suggest that the stimulatory effect of GLP-2 on SMA blood flow is NO-dependent and mediated via intrinsic, non-cholinergic enteric neurons.

Effects of non-competitive AMPA receptor antagonists injected into some brain areas of WAG/Rij rats, an animal model of generalized absence epilepsy

CFM-2 [1-(4-aminophenyl)-3,5-dihydro-7,8-dimethoxy-4H-2,3-benzodiazepin-4-one] and THIQ-10c [N-acetyl-1-(4-chlorophenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline], are two non-competitive 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl) propionic acid (AMPA) receptor antagonists, which demonstrated to antagonize generalized tonic-clonic seizures in different animal models. We have evaluated the effects of such compounds in a genetic animal model of absence epilepsy, the WAG/Rij rat. Animals were focally microinjected into specific brain areas of the cortico-thalamic circuit in order to evaluate the effects of these compounds on the number and duration of epileptic spike-wave discharges (SWDs) and better characterize the role of AMPA neurotransmission in this animal model. The focal microinjection of the two AMPA antagonists into some thalamic nuclei (ventralis posteromedialis (VPM), reticularis (NRT), ventralis posterolateralis (VPL) and the primary somatosensory forelimb region (S1FL)) was, generally, not able to significantly modify the occurrence of SWDs. Whereas, both compounds were able to reduce the number and duration of SWDs dose-dependently when microinjected into the peri-oral region of the primary somatosensory cortex (S1po). These findings suggest that AMPA receptor antagonists might play a role in absence epilepsies and that it might depend on the involvement of specific neuronal areas.

Benzodiazepinedione inhibitors of the Hdm2:p53 complex suppress human tumor cell proliferation in vitro and sensitize tumors to doxorubicin in vivo

The activity and stability of the p53 tumor suppressor are regulated by the human homologue of the mouse double minute 2 (Hdm2) oncoprotein. It has been hypothesized that small molecules disrupting the Hdm2:p53 complex would allow for the activation of p53 and result in growth suppression. We have identified small-molecule inhibitors of the Hdm2:p53 interaction using our proprietary ThermoFluor microcalorimetry technology. Medicinal chemistry and structure-based drug design led to the development of an optimized series of benzodiazepinediones, including TDP521252 and TDP665759. Activities were dependent on the expression of wild-type (wt) p53 and Hdm2 as determined by lack of potency in mutant or null p53-expressing cell lines or cells engineered to no longer express Hdm2 and wt p53. TDP521252 and TDP665759 inhibited the proliferation of wt p53-expressing cell lines with average IC(50)s of 14 and 0.7 micromol/L, respectively. These results correlated with the direct cellular dissociation of Hdm2 from wt p53 observed within 15 minutes in JAR choriocarcinoma cells. Additional activities of these inhibitors in vitro include stabilization of p53 protein levels, up-regulation of p53 target genes in a DNA damage-independent manner, and induction of apoptosis in HepG2 cells. Administration of TDP665759 to mice led to an increase in p21(waf1/cip1) levels in liver samples. Finally, TDP665759 synergizes with doxorubicin both in culture and in an A375 xenograft model to decrease tumor growth. Taken together, these data support the potential utility of small-molecule inhibitors of the Hdm2:p53 interaction for the treatment of wt p53-expressing tumors.

Modulation of cholinephosphotransferase activity in breast cancer cell lines by Ro5-4864, a peripheral benzodiazepine receptor agonist

Changes in phospholipid and fatty acid profile are hallmarks of cancer progression. Increase in peripheral benzodiazepine receptor expression has been implicated in breast cancer. The benzodiazepine, Ro5-4864, increases cell proliferation in some breast cancer cell lines. Biosynthesis of phosphatidylcholine (PC) has been identified as a marker for cells proliferating at high rates. Cholinephosphotransferase (CPT) is the terminal enzyme for the de novo biosynthesis of PC. We have addressed here whether Ro5-4864 facilitates some cancer causing mechanisms in breast cancer. We report that cell proliferation increases exponentially in aggressive breast cancer cell lines 11-9-1-4 and BT-549 when treated with nanomolar concentrations of Ro5-4864. This increase is seen within 24 h of treatment, consistent with the cell doubling time in these cells. Ro5-4864 also upregulates c-fos expression in breast cancer cell lines 11-9-1-4 and BT-549, while expression in non-tumorigenic cell line MCF-12A was either basal or slightly downregulated. We further examined the expression of the CPT gene in breast cancer (11-9-1-4, BT-549) and non-tumorigenic cell lines (MCF-12A, MCF-12F). We found that the CPT gene is overexpressed in breast cancer cell lines compared to the non-tumorigenic cell lines. Furthermore, the activity of CPT in forming PC is increased in the breast cancer cell lines cultured for 24 h. Additionally, we examined the CPT activity in the presence of nanomolar concentrations of Ro5-4864. Biosynthesis of PC was increased in breast cancer cell lines upon treatment. We therefore propose that Ro5-4864 facilitates PC formation, a process important in membrane biogenesis for proliferating cells.

Regulation of leptin distribution between plasma and cerebrospinal fluid by cholecystokinin receptors

Cholecystokinin (CCK) is a postprandial hormone that elicits a satiating effect and regulates feeding behaviour. CCK has been shown to enhance the effect of leptin in several experimental paradigms. The goal of this work was to characterize the effect of endogenous CCK on plasma leptin content by using CCK receptor antagonists. Therefore, we administered SR-27897, a selective CCK1 receptor antagonist, and L-365260, a selective CCK2 receptor antagonist, to fed and food-deprived rats and determined plasma leptin concentration by enzyme immunoassay. Plasma insulin and glucose concentration as well as food intake were also determined. Under our conditions, SR-27897 increased plasma concentration of leptin both in fed and food-deprived rats. It also increased food intake as well as plasma concentration of insulin in fed animals. L-365260 increased plasma leptin concentration only in fed rats. In animals receiving exogenous leptin, CCK-8 increased the ratio between the concentration of leptin in cerebrospinal fluid and plasma. These results show that CCK receptor antagonists increases plasma concentration of leptin and suggest that endogenous CCK may facilitate the uptake of plasma leptin to the cerebrospinal fluid.

Antinociceptive effects of peripheral benzodiazepine receptors

Pretreatment of mice with Ro5-4864 or PK11195 inhibited the first- and second-phase responses in the formalin test and this effect was significantly reversed by aminoglutethimide, an inhibitor of pregnenolone synthesis, suggesting that the antinociceptive effect of the peripheral-type benzodiazepine receptor ligands is dependent on steroid formation. Doses of Ro5-4864 that did not produce an antinociceptive effect when injected by the intraperitoneal route presented an analgesic effect, if infected by the intracerebroventricular, intrathecal or intraplantar routes. PK11195 pretreatments with intrathecal, intracerebroventricular or intraplantar doses had no effect in the formalin test. These results suggest that the antinociceptive effect of Ro5-4864 reflects the influence of this ligand on steroid production not only in many nonneuronal peripheral tissues but also in the nervous system, while the antinociceptive action of PK11195 may be due to the stimulation of steroid synthesis only in nonnervous tissues.

Antidepressant-like effect of Ro5-4864, a peripheral-type benzodiazepine receptor ligand, in forced swimming test

This study examined the effects of peripheral-type benzodiazepine receptors in the forced swimming test. PK 11195 (1-(2-chloro-phenyl)-N-methyl-N-(1-methylpropyl)-1-isoquinoline carboxamide) and Ro5-4864 (7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepine-2-one) were i.p. injected in mice, according to an acute (1 or 24 h) and a repeated (14 days) schedule. Pretreatment with the agonist, Ro5-4864, significantly reduced immobility time 1 h after treatment but not 24 h after it, whereas the antagonist, PK11195, did not interfere with the test parameters. Nevertheless, PK11195 pretreatment inhibited the Ro5-4864 antidepressant-like effect. Animals repeatedly treated with Ro5-4864 had a similar profile of action with no sign of motor impairment or locomotor activation as evaluated in the rota-rod and open-field tests, respectively. Aminoglutethimide pretreatment, which blocks the early step of steroid synthesis, inhibited the antidepressant-like effect of Ro5-4864. The present findings suggest an antidepressant-like profile for the benzodiazepine, Ro5-4864, that seems to involve steroid synthesis as underlying mechanism.

A randomised, double blind, placebo controlled crossover study of the cholecystokinin 2 antagonist L-365,260 as an adjunct to strong opioids in chronic human neuropathic pain

The aim of this study was to establish if the cholecystokinin (CCK) 2 antagonist L-365,260 augments the analgesic effect of morphine in human subjects with chronic neuropathic pain. This is a randomised, double blind, placebo controlled study of 40 adult subjects taking morphine for neuropathic pain. Each received placebo, L-365,260 30 mg and L-365,260 120 mg in three divided doses daily separated by a washout period in random order. Pain, activity, sedation, sleep and side effects were recorded along with 12 lead ECGs, renal and liver function tests and full blood pictures. L-365,260 failed to augment the analgesic effect of morphine at any of the dose levels used. Side effects were minor. There were no changes in ECGs and biochemical indices were unaltered with its use. The CCK 2 antagonist L-365,260 does not augment the analgesic effect of morphine in subjects with chronic neuropathic pain. L-365,260 was well tolerated and side effects from its use were minor.

Effects of evodiamine on gastrointestinal motility in male rats

The effects of evodiamine on gastric emptying, gastrointestinal transit, and plasma levels of cholecystokinin (CCK) were studied in male rats. Evodiamine, isolated from the dry unripened fruit of Evodia rutaecarpa Bentham (a Chinese medicine named Wu-chu-yu), has been recommended for abdominal pain, acid regurgitation, nausea, diarrhea, and dysmenorrhea. Gastrointestinal motility was assessed in rats 15 min after intragastric instillation of a test meal containing charcoal and Na(2)51CrO(4). Gastric emptying was determined by measuring the amount of radiolabeled chromium contained in the small intestine as a percentage of the initial amount received. Gastrointestinal transit was evaluated by calculating the geometric center of distribution of the radiolabeled marker. Blood samples were collected for CCK radioimmunoassay (RIA). After administration of evodiamine (0.67-6.00 mg/kg), both gastric emptying and gastrointestinal transit were inhibited, whereas the plasma concentration of CCK was increased in a dose-dependent manner. The selective CCK(1) receptor antagonists, devazepide and lorglumide, effectively attenuated the evodiamine-induced inhibition of gastric emptying and gastrointestinal transit. L-365,260 (3R-(+)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepine-3-yl)-N'-(3-methylphenyl)-urea), a selective CCK(2) receptor antagonist, did not alter the evodiamine-induced inhibition of gastric emptying and gastrointestinal transit. These results suggest that evodiamine inhibits both gastric emptying and gastrointestinal transit in male rats via a mechanism involving CCK release and CCK(1) receptor activation.

Reactivation of cocaine conditioned place preference induced by stress is reversed by cholecystokinin-B receptors antagonist in rats

The effects of different cholecystokinin (CCK) receptor antagonists (devazepide and L365,260) on cocaine or stress-induced reactivation of cocaine conditioned place preference (CPP) were investigated in rats. After receiving alternate injection of cocaine (10 mg/kg) and saline for 8 consecutive days, the rats spent more time in the drug-paired side (cocaine CPP) on day 9. These animals did not show cocaine CPP on day 31 following saline-paired training daily from days 10 to 30 (21-day extinction). However, a single injection of cocaine (10 mg/kg) or 15 min of intermittent footshock could reinstate CPP on day 32 with significant more time spent in the drug-paired side in comparison with that on day 0. Systemic injection of CCK-A receptor antagonists, devazepide (0.1 and 1 mg/kg, i.p.), 30 min before cocaine priming, significantly attenuated cocaine-induced reinstatement of CPP, while CCK-B receptor antagonist, L365,260 (0.1 and 1 mg/kg, i.p.), did not show a similar effect. In contrast, pretreatment with L365,260 (0.1 and 1 mg/kg, i.p.) but not devazepide (0.1 and 1 mg/kg, i.p.) significantly blocked stress-induced reinstatement of CPP. In another experiment, CCK-A or B receptor antagonists were infused into nucleus accumbens or amygdala to determine which brain area are involved in the role of different CCK receptors in stress or drug-induced relapse to cocaine seeking. The results show that infusion of the devazepide (10 microg) into the nucleus accumbens significantly inhibited the cocaine-induced reinstatement of CPP, while infusion of devazepide (1 and 10 microg) into amygdala did not affect cocaine-induced reactivation of CPP. Interestingly, infusion of L365,260 (1 and 10 microg) into both nucleus accumbens or amygdala significantly attenuated or blocked stress-induced reinstatement of CPP. These findings demonstrate that CCK-A and B receptor have different roles in relapse to drug craving and further suggest that the brain areas involved in the CCK receptors on reinstatement of drug seeking are not identical. CCK-B receptor antagonists might be of some value in the treatment and prevention of relapse to stress-induced to drug craving following long-term detoxification.

Mobilization of rat stomach ECL-cell histamine in response to short- or long-term treatment with omeprazole and/or YF 476 studied by gastric submucosal microdialysis in conscious rats

1. Mobilization of histamine from the ECL cells was monitored by gastric submucosal microdialysis in conscious rats. The ECL cells are known to operate under gastrin control and the purpose of the present study was to examine their in situ response to short-term (12 h) as well as long-term (28 days) hypergastrinaemia, induced by treatment with the proton pump inhibitor omeprazole. 2. Hypergastrinaemia promptly raised the histamine concentration in the microdialysate. The effect was prevented by CCK(2) receptor blockade (YF476). On day 7 of omeprazole treatment the microdialysate histamine concentration reached a peak, five times higher than before treatment. Subsequently (14 and 28 days), less histamine was mobilized. 3. Gastrin infusion (4 h) raised the microdialysate histamine concentration in a dose-dependent manner in fasted rats and freely fed rats and in rats treated with omeprazole for a week. However, while fasted and fed rats responded to low doses of gastrin, the omeprazole-treated rats required large doses of gastrin to respond. 4. When the amount of histamine mobilized was related to the serum gastrin concentration the following EC(50) values could be calculated: fasted rats 2.3 x 10(-10) M, freely fed rats 2.5 x 10(-10) M, omeprazole-treated rats 8.7 x 10(-10) M. The maximal histamine responses in the three groups were 18.4 pmol 4 h(-1)+/-0.8, 21.9 pmol 4 h(-1)+/-1.2 and 68.0 pmol 4 h(-1)+/-3.5, respectively. 5. The results suggest that ECL cells, exposed to a high gastrin concentration for a week, respond with a shift in the receptor-ligand binding affinity from high to low. Apparently, CCK(2) receptors of the ECL cells are subject to dynamic changes with respect to ligand-binding affinity.

Long-lasting cholecystokinin(2) receptor blockade after a single subcutaneous injection of YF476 or YM022

Histamine-forming ECL cells in the rat stomach operate under the control of gastrin. They represent a convenient target for studying cholecystokinin-B/gastrin (CCK(2)) receptor antagonists in vivo. We examined the effectiveness and duration of action of two CCK(2) antagonists, YM022 and YF476, with respect to their effect on ECL-cell histidine decarboxylase (HDC) activity in the rat. Oral administration of subcutaneous deposition of YF476 or YM022 reduced the HDC activity. The maximum/near-maximum dose for both drugs and for both modes of administration was 300 micromol kg(-1) (effects measured 24 h after dose). At this dose and time the serum concentration of YF476 was 20 - 40 nmol l(-1). The dose 300 micromol kg(-1) was used in all subsequent studies. A single subcutaneous injection of YF476 inhibited the HDC activity for 8 weeks. The circulating concentration of YF476 remained high for the same period of time (>/=15 nmol l(-1)). Subcutaneous YM022 suppressed the HDC activity for 4 weeks. A single oral dose of YF476 or YM022 inhibited the HDC activity for 2 - 3 days. Chronic gastric fistula rats were used to study the effect of subcutaneous YF476 on gastrin-stimulated acid secretion. A single injection of YF476 prevented gastrin from causing an acid response for at least 4 weeks (the longest time studied). We conclude that a single subcutaneous injection of 300 micromol kg(-1) YF476 causes blockade of CCK(2) receptors in the stomach of the rat for 8 weeks thus providing a convenient method for studies of the consequences of long-term CCK(2) receptor inhibition.

A locus and mechanism of action for associative morphine tolerance

Repeated administration of an opioid in the presence of specific environmental cues can induce tolerance specific to that setting (associative tolerance). Prolonged or repeated administration of an opioid without consistent contextual pairing yields non-associative tolerance. Here we demonstrate that cholecystokinin acting at the cholecystokinin-B receptor is required for associative but not non-associative morphine tolerance. Morphine given in the morphine-associated context increased Fos-like immunoreactivity in the lateral amygdala and hippocampal area CA1. Microinjection of the cholecystokinin B antagonist L-365,260 into the amygdala blocked associative tolerance. These results indicate that cholecystokinin acting in the amygdala is necessary for associative tolerance to morphine's analgesic effect.

Small intestinal and pancreatic microstructures are modified by an intraduodenal CCK-A receptor antagonist administration in neonatal calves

The aim of the present study was to investigate the role of CCK on the upper gut and pancreas microstructure and on pancreatic juice secretion in neonatal calves assessed by a repetitive intraduodenal administration of FK480, a CCK-A receptor antagonist, during the first 6 days of life. The experiment was performed on 10 neonatal calves surgically fitted with a pancreatic accessory duct catheter and duodenal cannulas. Calves were sacrificed on day 7 for tissue sampling. Treatment with FK480 resulted in: reduction of preprandial pancreatic juice secretion at days 1-3, smaller size of pancreatic acini and number of cells per acinus, reduction in intestinal crypt depth (except in the duodenal bulb), numerous modifications of intestinal villi length and width, lower mitotic index of crypt cells, and increased number and size of enterocytes with 'empty vacuoles'. In conclusion, the blockade of CCK-A receptors during early life both reduced pancreatic exocrine secretion and induced complex changes in pancreatic microstructure. The influence of CCK on the upper gut microstructure in neonatal calves could be either direct via activation of CCK-A receptors located in the mucosa of the upper gut or indirect by modulation of the secretion of pancreatic juice.

The role of the hippocampus and 5-HT/GABA interaction in the central effects of benzodiazepine receptor ligands

The effects of an intrahippocampal administering of a nonselective full (midazolam), a partial benzodiazepine (BDZ) receptor agonist (bretazenil), and a BDZ1 selective (zolpidem) receptor ligand were examined in the open field test (OFT) of neophobia and Vogel's test (VT) of conflict behavior in rats. Moreover, the influence of local injections of a noncompetitive GABA(A) receptor antagonist, picrotoxin, on the anxiolytic-like effect of serotonin (5-HT) depletion (p-chlorophenylalanine, p-CPA) in the Vogel test was studied. It was found that in the OFT only midazolam (0.1 microg/site) given to the hippocampus (HP) disinhibited rat exploratory behavior, whereas all the examined compounds inhibited animal motor activity when injected locally at 10.0 microg/site, the highest dose used in the tests. In the VT, again, only midazolam disinhibited rat conflict behavior on a dose-dependent basis. Picrotoxin administered to the HP produced a tendency to increase locomotor activity in rats, and significantly attenuated the anti-conflict action of serotonin depletion without changing the pain threshold and spontaneous drinking of the animals. p-CPA induced potent, dose-dependent and selective 5-HT and 5-hydroxyindoleacetic acid decrease in the HP after administering the dose used in the behavioral experiment. Thus, the present data provide evidence for the lack of selective anxiolytic activity of a partial non-selective agonist and a full selective agonist at the BDZ1 receptor after their administration to the HP. The model of intra-HP drug injections appeared effective in discriminating the anxiolytic spectrum of activity of new psychotropic compounds. Moreover, the obtained results indicate that the dorsal HP is one of the central sites important for GABA/5-HT interaction that modulates rat emotional behavior.

Synthesis and characterization of orally active nonpeptide vasopressin V2 receptor antagonists

The present study was undertaken to evaluate whether a novel series of 2,6-diaza-5-oxobicyclo[5.4.0]undeca-1(7),8,10-triene derivatives exhibited antagonistic activity for vasopressin V1 and V2 receptors. Most of these compounds were synthesized and showed a high affinity potential for V2 receptor and low to moderate affinity potential for V1 receptor. The most potent and V2-selective compound, N-[4-[2,6-diaza-6-[2-(4-methylpiperazinyl)-2-oxoethyl] -5- oxobicyclo[5.4.0]undeca-1(7),8,10-trien-2-yl]-carbonyl]pheny l][2-(4- methylphenyl)phenyl]-formamide (11b), exhibited IC50's of 2.9 nM for the V2 receptor and 200 nM for the V1 receptor, respectively. When administered orally to rat, 11b showed an approximately 18-fold increased urine volume in comparison with control rat.

Effect of ionizing radiation on the release of cholecystokinin in the hypothalamus of the rat

This study was designed to identify the mechanisms underlying the reduction in food intake in rats. Measurements were made of the release of cholecystokinin (CCK) stimulated by potassium chloride in the hypothalamus after (a) gamma irradiation (60Co), (b) treatment with the CCK-A and CCK-B antagonists L-364,718 and L-365,260 with and without radiation, (c) bilateral abdominal vagotomy, and (d) vagotomy with and without radiation and with and without L-364,718. The concentrations of CCK in hypothalamus perfusate were measured by a radioimmunoassay. Exposure of rats to 1, 3, 5 and 10 Gy (1 Gy/min) increased release of CCK in the hypothalamus in a manner that was dependent on dose. A dose of 5 Gy was chosen for further studies. Intraperitoneal (i.p.) administration of 10, 20 and 50 microg/kg of L-364,718 did not induce significant changes in release of CCK in sham-irradiated animals. However, the drug decreased the release of CCK induced by radiation in a dose-dependent manner. In contrast to L-364,718, 20-50 microg/kg of L-365,260 decreased the release of CCK in the hypothalamus in sham-irradiated animals but did not decrease release of CCK induced by exposure to radiation. Vagotomy produced an insignificant reduction in release of CCK compared to that in sham-irradiated controls. However, vagotomy decreased release of CCK in irradiated rats compared to the irradiated rats without vagotomy. Vagotomy and i.p. administration of 10, 20 and 50 microg/kg of L-364,718 decreased release of CCK in irradiated rats compared to that in irradiated rats without vagotomy. However, i.p. administration of 10, 20 and 50 microg/kg of L-364,718 did not induce significant decreases in release of CCK in the hypothalamus of vagotomized and irradiated animals compared to those in rats that were vagotomized and irradiated but not treated with L-364,718. These results demonstrate that radiation increases the release of CCK in the hypothalamus, and that this effect is inhibited by vagotomy and the administration of a CCK-A receptor antagonist. A CCK-A receptor antagonist may be used to mitigate a radiation-induced deficit in food intake.

Clobazam in partial status epilepticus

Clobazam is the first and only 1,5-benzodiazepine to be used in the management of epilepsy. The use and effectiveness of oral clobazam in patients with status epilepticus has only been previously described in one study of 16 cases, seven of whom were in complex partial status. We have used clobazam in four patients with EEG-proven partial status epilepticus refractory to standard antiepileptic drugs. In all cases, except one, the seizure activity was controlled within 2 hr of administering clobazam. Our four patients responded promptly to an oral loading of clobazam which was approximately twice the usual daily maintenance dose. The drug was well tolerated and no adverse effects were seen. Clobazam's effectiveness as a first-line agent remains to be studied. Further controlled studies are recommended.

Outcome evaluation of gabapentin as add-on therapy for partial seizures. "NEON" Study Investigators Group. Neurontin Evaluation of Outcomes in Neurological Practice

OBJECTIVE

The safety, tolerability, efficacy, and impact on quality of life of gabapentin (Neurontin) as adjunctive therapy to carbamazepine (CBZ) and/or phenytoin (PHT) was assessed in epileptic patients with partial seizures.

METHODS

NEON (Neurontin Evaluation of Outcomes in Neurological Practice) was an open-label, prospective, multicentre study conducted in patients on a stable dose of CBZ and/or PHT and experiencing an average of up to 4 complex partial seizures with or without secondary generalization per month, with no seizure-free months. The treatment lasted 20 weeks. Gabapentin was started at 400 mg/day and was individually titrated to effective tolerable dose up to 2400 mg/day. Quality of life was evaluated using the QOLIE-10 questionnaire.

RESULTS

A total of 141 patients were enrolled at 36 sites; 114 patients were evaluable for efficacy analyses. The mean maintenance dose of gabapentin was 1600 mg/day (range = 300-3200). A decrease of 50% or more in frequency of complex partial + secondary generalized seizures was observed in 81 (71%) patients (p = 0.0001). Fifty two (46%) patients were seizure-free during the last 8 weeks of treatment. A significant improvement (p < 0.05) was observed in 5 of the 10 questions of the QOLIE-10, as well as in the composite QOL score (p = 0.0002). The most frequent adverse events included somnolence (16%), dizziness (9%), and asthenia (6%). Twenty-five (18%) patients prematurely discontinued the study, 16 (11%) of them due to adverse events.

CONCLUSIONS

This study indicates that treatment with gabapentin as adjunctive therapy to standard antiepileptic drugs in this group of patients not only provides significant improvement in seizure control, but also has a positive impact on quality of life. The clinical benefits in efficacy, safety and tolerability demonstrated at 20 weeks are sustained, and no tolerance develops with gabapentin in longer term use.

Cholecystokinin satiety involves CCKA receptors perfused by the superior pancreaticoduodenal artery

Three experiments compared the potency of the type A cholecystokinin (CCKA)-receptor antagonist devazepide for increasing intake of 30% sucrose when injected into the superior pancreaticoduodenal (SPD) artery (SPD group) or jugular vein (IV group). In experiment 1, 15 min of sucrose intake in adult, male Sprague-Dawley rats after 6 h of food deprivation was increased by devazepide (20 micrograms/kg) administered into the SPD artery whether given alone or in conjunction with cholecystokinin octapeptide (CCK-8, 2 micrograms/kg ip). Devazepide had no effect in the IV group. In experiment 2, injection of 8, 20, and 50 micrograms/kg of devazepide into the SPD artery increased sucrose intake of nondeprived rats. Only the highest dose was effective in the IV group. On subsequent tests, administration of 1 microgram/kg of CCK-8 significantly suppressed intake only in the SPD group. In experiment 3, nondeprived rats with SPD artery and jugular vein catheters were tested in a within-subjects design. Devazepide (20 micrograms/kg) increased sucrose intake after injection into the SPD artery, but not into the jugular vein. In experiment 4, intraduodenal devazepide (8, 20, and 50 micrograms/kg) had no effect. These results indicate that CCKA receptors within the SPD arterial bed mediate the satiating action of CCK, consistent with local action of duodenal CCK.

Intracerebroventricular cholecystokinin A-receptor antagonist does not reduce satiation by endogenous CCK

Suppression of sham feeding by exogenous CCK-8 or intraintestinal oleate infusion is attenuated by peripheral administration of the CCK-A receptor antagonist, devazepide, but not by the CCK-B antagonist, L365260. Likewise, systemically administered devazepide increases food intake by real feeding rats. These results suggest that endogenous CCK participates in the reduction of food intake by intestinal oleate and ingested food. Although originally categorized as a "peripheral" receptor subtype, the CCK-A receptor is also present in the brain. In an effort to examine whether devazepide acts in the brain or in the periphery to attenuate suppression of food intake by intraintestinal oleate, we injected devazepide into the lateral or fourth cerebral ventricles of intraintestinally infused, sham-fed rats. We also compared the ability of intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) devazepide to elicit increased food intake in real feeding rats. Doses of devazepide that were sufficient to attenuate or abolish oleate-induced suppression of sham feeding, when administered i.p., failed to attenuate suppression of intake when administered i.c.v., i.p. devazepide also was more effective than i.c.v. devazepide for attenuation of the suppression of sham feeding by i.p. injection of exogenous CCK-8. Finally, i.c.v. devazepide was ineffective for increasing real food intake, whereas the same dose administered i.p. significantly increased food intake. Our results do not support participation of brain CCK-A receptors in the suppression of food intake by exogenous CCK, or by endogenous CCK released after intraintestinal oleate infusion, or food intake.

Devazepide, a CCK(A) antagonist, attenuates the satiating but not the preference conditioning effects of intestinal carbohydrate infusions in rats

Endogenous cholecystokinin (CCK) is thought to participate in the satiating action of foods, and some data suggest that it may also mediate their postingestive reinforcing effects. This was investigated by determining if the CCK(A) receptor antagonist, devazepide, attenuates flavor preference conditioning by intraduodenal (I.D.) carbohydrate infusions. In Experiment 1, food-restricted female rats were trained 30 min/day to associate a cue flavor (CS+) with I.D. infusions of 8% Polycose and a different flavor (CS ) with I.D. water infusions. Half of the rats (DEV group) were pretreated with devazepide (300 microg/kg body weight) and the other half (CON group) with vehicle, 30 min prior to CS training sessions and choice tests. Both groups displayed similar CS+ preferences (CON: 68%; DEV: 69%). In contrast, devazepide blocked the feeding inhibitory effects of I.D. Polycose infusion and cholecystokinin octapeptide injection in Experiment 2. A higher dose of devazepide (1200 microg/kg) also failed to inhibit preference conditioning by I.D. Polycose in Experiment 3. These results indicate that, although CCK(A) mechanisms play a role in the satiating effect of I.D. carbohydrates, they do not mediate their reinforcing effect. The present study, along with other recent reports, indicate that different mechanisms mediate the satiating and reinforcing actions of nutrients.

[The effect of gidazepam on the cardiovascular system function in patients with neurotic reactions and in healthy subjects under aggravated conditions]

Administration of 0.05 g gidazepam once or twice daily for 7 days increased the stroke volume (SV) and circulation volume (CV) and reduced total peripheral resistance in neurotic patients. In healthy individuals 0.05 g gidazepam administered 60 min before an important examination stabilized CV. In subjects kept for 60 min in a microclimate with increasing temperature (55 +/- 2 degrees C, relative humidity 75-80%, rate of movement 1.5 m/min, rectal temperature at the end of exposure 39 degrees C) 0.05 g gidazepam administered 60 min before overheating optimally reorganized the reaction of the cardiovascular system, stabilized the SV at the initial level, which together with the growing heart rate increased the CV and provided sufficient perfusion of the vital organs. In healthy subjects working as operators for 4 h under conditions of hypercapnia (1.5% CO2), a single administration of 0.05 g gidazepam one hour before the beginning of work reduced the pulse pressure and increased the SV. The results obtained are evidence of the safety of using gidazepam as a corrector of emotion-induced disorders in operator performance under extreme conditions.

[Multi-drug antiemetic treatment and effect of treatment duration of concurrent steroids--for complete control of chemotherapy-induced nausea/vomiting in gynecological cancer]

Antiemetic effect and safety of concurrent administration of ondansetron and other antiemetics (dexamethasone, domperidone and ethyl loflazepate), given for complete suppression of nausea/vomiting, were examined in 46 patients (109 courses) with gynecological cancer receiving single high-dose of cisplatin or carboplatin. As for the delayed emesis, antiemetic effect depending on the steroid treatment duration, given concurrently to ondansetron, was compared. The results were as follows; 1. In 78 courses, anticancer drugs were given concurrently to cisplatin or carboplatin only on Day 1. In the remaining 31 courses, those drugs were concurrently administered up to Day 6 at the longest. 2. Complete suppression (i.e., no onsets) rate of acute emesis was 64.2% (70/109 courses) for nausea, and 84.4% (92/109 courses) for vomiting. 3. When the complete suppression depending on duration of concomitant steroid was examined mainly in patients receiving CAP (cyclophosphamide, adriamycin and cisplatin), higher antiemetic effect, especially in nausea, was observed in those on concomitant steroids for 3 days compared to that for 1 day. 4. The food intake rate improved along with nausea symptoms. 5. No adverse event or laboratory abnormality due to the multi-antiemetic treatment was observed. Based on the above, the efficacy of the antiemetic treatment in this study was confirmed. In delayed emesis, concurrent steroids given for 3 days after chemotherapy were considered effective and were also regarded to improve food intake.

[An experimental model of benzodiazepine intoxication]

It has been demonstrated in rat experiments that intraperitoneal injection of 100 mg/kg phenazepam immobilizes the animals for one hour, causes long-term diminution of the muscular tonus and disturbed coordination of movements, tachycardia, hypotension, hyperthermia, depression of orientation and exploration motor activity, and disturbance of conditioned reflexes of active and passive avoidance. It is concluded that the changes in the above-indicated parameters of autonomic and behavioral status of rats under the effect of a 100 mg/kg dose of phenazepam are clearly expressed for a long period of time, are specific to the effect of benzodiazepines and may therefore serve as a model of severe BD intoxication for evaluating the efficacy of their antidotes. This has been confirmed in experiments with the well-known BD antagonist phlumazelin.

Cholecystokinin receptors do not mediate the behavioral effects of lipopolysaccharide in mice

To test the possible role of cholecystokinin (CCK) in the decrease of social exploration induced by intraperitoneal (IP) injection of lipopolysaccharide (LPS, 100 microg/kg), mice were pretreated with IP or intracerebroventricular (ICV) injection of the CCKA receptor antagonist L-364,718 (3 mg/kg and 10 microg/kg, respectively) and the CCKB receptor antagonist L-365,260 (1 mg/kg and 10 microg/kg, respectively). L-364,718 and L-365,260 did not alter LPS-induced decrease in social investigation, whatever the route of administration, suggesting that endogenous cholecystokinin does not mediate the effect of proinflammatory cytokines on social exploration in mice.

Negative myoclonic status due to antiepileptic drug tapering: report of three cases

PURPOSE

Epileptic negative myoclonus (ENM) has been increasingly recognized in different epilepsies, but the reasons for its appearance and prognosis remain uncertain. We report 3 patients who developed de novo, almost continuous ENM, triggered by antiepileptic drug (AED) tapering, that resolved with treatment.

METHODS

Three patients aged 16, 19, and 65 years with a 13- to 36-year history of partial epilepsy were receiving a therapeutic dosage of carbamazepine or phenobarbital plus either clobazam (CLB) or valproate (VPA). None had previously had ENM. Forty-eight to 72 h after CLB or VPA withdrawal, the habitual seizures recurred. The patient also began to report repetitive postural lapses of one or more limbs that interfered with eating or writing. At this time, each patient underwent polygraphy with simultaneous surface electromyography (EMG) of deltoid, biceps, and triceps muscles and of the wrist extensor and flexor bilaterally.

RESULTS

In all patients, EEGs demonstrated almost continuous epileptiform discharges whose spatial distribution was similar to that observed before ENM appearance. Polygraphic recordings showed repetitive loss of postural EMG activity in one or more limbs, 100-400 ms in duration, which occurred in conjunction with the spike-waves. One milligram of clonazepam intravenously always terminated ENM status, which has not recurred in the ensuing 9-36 months.

CONCLUSIONS

ENM may emerge as a new type of seizure due to tapering of AED therapy. This effect is possibly related to the great activation of epileptiform activity with consequent interference with cortical activity.

Effect of a cholecystokinin-A receptor blocker on protein-induced food intake suppression in rats

To test the hypothesis that only dietary protein (Pro; chicken egg albumin) and not amino acids (AA), carbohydrates (CHO; cornstarch), or fats (Fat; corn oil) produces a satiating effect via cholecystokinin (CCK) receptors, devazepide was coadministered with each macronutrient. Given alone (in 4 ml ig), Pro (0.75, 1.0, and 1.5 g), AA (1.0 g), CHO (1.4 g), and Fat (2.4 g) suppressed (P < 0.05) food intake in the first hour by 0.5, 0.8, and 1.1 g; 1.9 g; and 1.0 g, respectively, and in the first 2 h of feeding by 0.8, 1.2, and 1.3 g; 1.7 g; 0.7 g; and 1.5 g, respectively. When coadministered with devazepide (0.5 mg/kg body wt ig), the suppression of food intake caused by Pro, AA, CHO, and Fat treatments was modulated in the first hour by 60, 50, and 55%; 16%, 11%; and 10%, respectively, and during 0-2 h by 63, 92, and 54%; 29%; 0%; and -20%, respectively. Devazepide (0.5 mg/kg) given intraperitoneally also modulated Pro intake suppression during the first hour by 33% and during 0-2 h by 79%. Devazepide appears to interact with mechanisms of Pro-induced food intake suppression, but not AA-, Fat-, or CHO-induced food intake suppression. These studies provide evidence that CCK receptors play a role in Pro (albumin)- but not AA-, CHO (corn starch)-, or Fat (corn oil)-induced food intake suppression in rats.

In mononeuropathic rats, the enhancement of morphine antinociception by L-365,260, a selective CCK(B) receptor antagonist, depends on the dose of systemic morphine and stimulus characteristics

The ability of the selective cholecystokinin(B) (CCK(B)) receptor antagonist L-365,260 (0.2 mg/kg s.c.) to modulate the antinociceptive action of relatively low doses of systemic morphine (0.1, 0.3 and 1.0 mg/kg i.v.) was evaluated using a well established rat model of peripheral unilateral mononeuropathy. Behavioural tests based on both mechanical (vocalization threshold to paw pressure) and thermal (struggle latency after immersion of the paw into a cold (10 degrees C), warm (44 degrees C) or hot (46 degrees C) water bath) stimuli were used. Experiments were performed 2 weeks after the surgery when the pain-related behaviour has fully developed. We demonstrated a differential effect of L-365,260 depending both on the dose of morphine and the test used. Pretreatment with the CCK(B) receptor antagonist (0.2 mg/kg) inverted the ineffectiveness of the lowest dose (0.1 mg/kg i.v.) of morphine against the noxious (46 degrees C) thermal stimulus, and the effect of the combination was equal to that seen after the dose 0.3 mg/kg of morphine alone. Likewise, in the mechanical test, the already enhanced effect of this dose (0.1 mg/kg) of morphine on the nerve-injured paw was further increased (by 4-fold) after L-365,260 pretreatment. These effects were abolished by naloxone (0.01 mg/kg i.v.). However, the effects of the higher doses (0.3 and 1.0 mg/kg i.v.) of morphine against the mechanical or noxious thermal stimuli were not significantly enhanced by pretreatment with the CCK(B) receptor antagonist. Further, L-365,260 was found to be completely ineffective in modulating the responses to morphine at 10 degrees C and at 44 degrees C.

Activation of amygdala cholecystokininB receptors potentiates the acoustic startle response in the rat

The acoustic startle reflex is a sensitive index of "anxiety" and "fear." Potentiation of startle by conditioned and unconditioned fear stimuli appears to be mediated by the amygdala. CholecystokininB (CCKB) agonists increase "anxiety" in laboratory animals and induce "panic" in humans. Here, we investigate the role CCKB receptor-mediated mechanisms in the amygdala in the potentiation of startle. First, intra-amygdala infusions of the CCKB receptor agonist pentagastrin (0, 0.01, 0.1, 1, and 10 nM) produced a dose-related potentiation of acoustic startle responses. At the highest dose, startle amplitudes were increased up to 90% above preinfusion baseline levels. Second, similar infusions of pentagastrin had no effect on locomotor activity over the same time course, showing that increases in startle responsivity after infusions of pentagastrin are not attributable to nonspecific changes in motor activity. Third, infusions of similar doses of pentagastrin into the striatum or nucleus accumbens did not potentiate startle responses. Fourth, pretreatment with the CCKB receptor antagonist L-365,260 (0.1 mg/kg, i.p.) attenuated the potentiation of startle produced by intra-amygdala infusions of pentagastrin. Finally, intra-amygdala infusion of the CCKB receptor-selective antagonist PD-135158 (10 micro;g) blocked the potentiation of startle produced by i.c.v. infusions of pentagastrin, suggesting that i.c.v. infusions of pentagastrin potentiate startle responses via activation of amygdala CCKB receptors. These results show that amygdala CCKB receptor-mediated mechanisms are involved in the potentiation of acoustic startle responses.

[Importance of toxicological studies in animals for elaboration of pathogenetic therapy of hydrazine intoxication]

Pathogenesis of poisoning with hydrazine seems complicated. Hydrazines inhibit pyridoxal-dependent enzymes, interfere with carbohydrates transformation and lipid metabolism, alter the processes of energy metabolism. Treatment of poisoning with hydrazine is effective only when containing drug combinations. Based experimentally, recommendations on the combination (phenazepam, be methyl, piracetam, ionol) were supported by chemical testing of the drugs.

Evaluation of the specificity and potency of a series of cholecystokinin-B/gastrin receptor antagonists in vivo

The potency and specificity of five proposed cholecystokinin-B receptor antagonists, YM022, RP73870, L-740,093, L-365,260 and LY288513, were studied in rats and mice. Gastrin activates rat stomach histidine decarboxylase via cholecystokinin-B/gastrin receptors. To examine cholecystokinin-B receptor-mediated effects of the five drugs, they were infused intravenously to fasted rats and the histidine decarboxylase activity in the oxyntic mucosa was determined. While YM022, RP73870, L-740,093 and L-365,260 failed to activate histidine decarboxylase, they dose-dependently antagonized the gastrin-induced histidine decarboxylase activation. LY288513 had no effect in the doses tested. The maximal inhibitory effect of L-365,260, L-740,093, RP73870 and YM022 on histidine decarboxylase, activated by the intravenous infusion of an ED50 does of gastrin (0.4 nmoles/kg/hr), was seen at doses of 3, 0.3, 0.1 and 0.1 mumoles/kg/hr, respectively; the corresponding ID50 values were 0.4, 0.02, 0.007 and 0.004 mumoles/kg/h. In a follow-up study, YM022 and RP73870 were found to produce a rightward shift of the gastrin dose-response curve, which is consistent with competitive inhibition. The effect of the five drugs on a cholecystokinin-A receptor-mediated response was examined by studying gastric emptying in mice. Cholecystokinin-8s, given by a subcutaneous bolus injection, dose-dependently inhibits gastric emptying. The specific cholecystokinin-A receptor antagonist devazepide (given intravenously as a bolus injection) antagonized the effect of cholecystokinin-8s in a dose-dependent manner, with an ID50 value of 28 nmoles/kg. None of the drugs inhibited the gastric emptying or prevented the cholecystokinin-8s-induced effect at the doses tested. The results indicate that YM022, RP73870, L-740,093 and L-365,260 act as cholecystokinin-B receptor antagonists in vivo, being without measurable agonistic activity. Furthermore, they do not interact with cholecystokinin-A receptors at te doses tested. Among the cholecystokinin-B receptor antagonists studied YM022 and RP73870 are superior, the rank order of potency being YM022 > or = RP73870 > L-740,093 > L-365,260.